26 files changed, 3702 insertions, 0 deletions

diff --git a/p2p/src/backend.rs b/p2p/src/backend.rs
new file mode 100644
index 0000000..290e3e7
--- /dev/null
+++ b/p2p/src/backend.rs
@@ -0,0 +1,139 @@
+use std::sync::Arc;
+
+use log::info;
+
+use karyons_core::{pubsub::Subscription, Executor};
+
+use crate::{
+    config::Config,
+    discovery::{ArcDiscovery, Discovery},
+    monitor::{Monitor, MonitorEvent},
+    net::ConnQueue,
+    peer_pool::PeerPool,
+    protocol::{ArcProtocol, Protocol},
+    ArcPeer, PeerID, Result,
+};
+
+pub type ArcBackend = Arc<Backend>;
+
+/// Backend serves as the central entry point for initiating and managing
+/// the P2P network.
+///
+///
+/// # Example
+/// ```
+/// use std::sync::Arc;
+///
+/// use easy_parallel::Parallel;
+/// use smol::{channel as smol_channel, future, Executor};
+///
+/// use karyons_p2p::{Backend, Config, PeerID};
+///
+/// let peer_id = PeerID::random();
+///
+/// // Create the configuration for the backend.
+/// let mut config = Config::default();
+///
+/// // Create a new Backend
+/// let backend = Backend::new(peer_id, config);
+///
+/// // Create a new Executor
+/// let ex = Arc::new(Executor::new());
+///
+/// let task = async {
+///     // Run the backend
+///     backend.run(ex.clone()).await.unwrap();
+///
+///     // ....
+///
+///     // Shutdown the backend
+///     backend.shutdown().await;
+/// };
+///
+/// future::block_on(ex.run(task));
+///
+/// ```
+pub struct Backend {
+    /// The Configuration for the P2P network.
+    config: Arc<Config>,
+
+    /// Peer ID.
+    id: PeerID,
+
+    /// Responsible for network and system monitoring.
+    monitor: Arc<Monitor>,
+
+    /// Discovery instance.
+    discovery: ArcDiscovery,
+
+    /// PeerPool instance.
+    peer_pool: Arc<PeerPool>,
+}
+
+impl Backend {
+    /// Creates a new Backend.
+    pub fn new(id: PeerID, config: Config) -> ArcBackend {
+        let config = Arc::new(config);
+        let monitor = Arc::new(Monitor::new());
+
+        let conn_queue = ConnQueue::new();
+
+        let peer_pool = PeerPool::new(&id, conn_queue.clone(), config.clone(), monitor.clone());
+        let discovery = Discovery::new(&id, conn_queue, config.clone(), monitor.clone());
+
+        Arc::new(Self {
+            id: id.clone(),
+            monitor,
+            discovery,
+            config,
+            peer_pool,
+        })
+    }
+
+    /// Run the Backend, starting the PeerPool and Discovery instances.
+    pub async fn run(self: &Arc<Self>, ex: Executor<'_>) -> Result<()> {
+        info!("Run the backend {}", self.id);
+        self.peer_pool.start(ex.clone()).await?;
+        self.discovery.start(ex.clone()).await?;
+        Ok(())
+    }
+
+    /// Attach a custom protocol to the network
+    pub async fn attach_protocol<P: Protocol>(
+        &self,
+        c: impl Fn(ArcPeer) -> ArcProtocol + Send + Sync + 'static,
+    ) -> Result<()> {
+        self.peer_pool.attach_protocol::<P>(Box::new(c)).await
+    }
+
+    /// Returns the number of currently connected peers.
+    pub async fn peers(&self) -> usize {
+        self.peer_pool.peers_len().await
+    }
+
+    /// Returns the `Config`.
+    pub fn config(&self) -> Arc<Config> {
+        self.config.clone()
+    }
+
+    /// Returns the number of occupied inbound slots.
+    pub fn inbound_slots(&self) -> usize {
+        self.discovery.inbound_slots.load()
+    }
+
+    /// Returns the number of occupied outbound slots.
+    pub fn outbound_slots(&self) -> usize {
+        self.discovery.outbound_slots.load()
+    }
+
+    /// Subscribes to the monitor to receive network events.
+    pub async fn monitor(&self) -> Subscription<MonitorEvent> {
+        self.monitor.subscribe().await
+    }
+
+    /// Shuts down the Backend.
+    pub async fn shutdown(&self) {
+        self.discovery.shutdown().await;
+        self.peer_pool.shutdown().await;
+    }
+}
diff --git a/p2p/src/config.rs b/p2p/src/config.rs
new file mode 100644
index 0000000..ebecbf0
--- /dev/null
+++ b/p2p/src/config.rs
@@ -0,0 +1,105 @@
+use karyons_net::{Endpoint, Port};
+
+use crate::utils::Version;
+
+/// the Configuration for the P2P network.
+pub struct Config {
+    /// Represents the network version.
+    pub version: Version,
+
+    /////////////////
+    // PeerPool
+    ////////////////
+    /// Timeout duration for the handshake with new peers, in seconds.
+    pub handshake_timeout: u64,
+    /// Interval at which the ping protocol sends ping messages to a peer to
+    /// maintain connections, in seconds.
+    pub ping_interval: u64,
+    /// Timeout duration for receiving the pong message corresponding to the
+    /// sent ping message, in seconds.
+    pub ping_timeout: u64,
+    /// The maximum number of retries for outbound connection establishment.
+    pub max_connect_retries: usize,
+
+    /////////////////
+    // DISCOVERY
+    ////////////////
+    /// A list of bootstrap peers for the seeding process.
+    pub bootstrap_peers: Vec<Endpoint>,
+    /// An optional listening endpoint to accept incoming connections.
+    pub listen_endpoint: Option<Endpoint>,
+    /// A list of endpoints representing peers that the `Discovery` will
+    /// manually connect to.
+    pub peer_endpoints: Vec<Endpoint>,
+    /// The number of available inbound slots for incoming connections.
+    pub inbound_slots: usize,
+    /// The number of available outbound slots for outgoing connections.
+    pub outbound_slots: usize,
+    /// TCP/UDP port for lookup and refresh processes.
+    pub discovery_port: Port,
+    /// Time interval, in seconds, at which the Discovery restarts the
+    /// seeding process.
+    pub seeding_interval: u64,
+
+    /////////////////
+    // LOOKUP
+    ////////////////
+    /// The number of available inbound slots for incoming connections during
+    /// the lookup process.
+    pub lookup_inbound_slots: usize,
+    /// The number of available outbound slots for outgoing connections during
+    /// the lookup process.
+    pub lookup_outbound_slots: usize,
+    /// Timeout duration for a peer response during the lookup process, in
+    /// seconds.
+    pub lookup_response_timeout: u64,
+    /// Maximum allowable time for a live connection with a peer during the
+    /// lookup process, in seconds.
+    pub lookup_connection_lifespan: u64,
+    /// The maximum number of retries for outbound connection establishment
+    /// during the lookup process.
+    pub lookup_connect_retries: usize,
+
+    /////////////////
+    // REFRESH
+    ////////////////
+    /// Interval at which the table refreshes its entries, in seconds.
+    pub refresh_interval: u64,
+    /// Timeout duration for a peer response during the table refresh process,
+    /// in seconds.
+    pub refresh_response_timeout: u64,
+    /// The maximum number of retries for outbound connection establishment
+    /// during the refresh process.
+    pub refresh_connect_retries: usize,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Config {
+            version: "0.1.0".parse().unwrap(),
+
+            handshake_timeout: 2,
+            ping_interval: 20,
+            ping_timeout: 2,
+
+            bootstrap_peers: vec![],
+            listen_endpoint: None,
+            peer_endpoints: vec![],
+            inbound_slots: 12,
+            outbound_slots: 12,
+            max_connect_retries: 3,
+            discovery_port: 0,
+            seeding_interval: 60,
+
+            lookup_inbound_slots: 20,
+            lookup_outbound_slots: 20,
+            lookup_response_timeout: 1,
+            lookup_connection_lifespan: 3,
+            lookup_connect_retries: 3,
+
+            refresh_interval: 1800,
+            refresh_response_timeout: 1,
+            refresh_connect_retries: 3,
+        }
+    }
+}
diff --git a/p2p/src/discovery/lookup.rs b/p2p/src/discovery/lookup.rs
new file mode 100644
index 0000000..f404133
--- /dev/null
+++ b/p2p/src/discovery/lookup.rs
@@ -0,0 +1,366 @@
+use std::{sync::Arc, time::Duration};
+
+use futures_util::{stream::FuturesUnordered, StreamExt};
+use log::{error, trace};
+use rand::{rngs::OsRng, seq::SliceRandom, RngCore};
+use smol::lock::{Mutex, RwLock};
+
+use karyons_core::{async_utils::timeout, utils::decode, Executor};
+
+use karyons_net::{Conn, Endpoint};
+
+use crate::{
+    io_codec::IOCodec,
+    message::{
+        get_msg_payload, FindPeerMsg, NetMsg, NetMsgCmd, PeerMsg, PeersMsg, PingMsg, PongMsg,
+        ShutdownMsg,
+    },
+    monitor::{ConnEvent, DiscoveryEvent, Monitor},
+    net::{ConnectionSlots, Connector, Listener},
+    routing_table::RoutingTable,
+    utils::version_match,
+    Config, Error, PeerID, Result,
+};
+
+/// Maximum number of peers that can be returned in a PeersMsg.
+pub const MAX_PEERS_IN_PEERSMSG: usize = 10;
+
+pub struct LookupService {
+    /// Peer's ID
+    id: PeerID,
+
+    /// Routing Table
+    table: Arc<Mutex<RoutingTable>>,
+
+    /// Listener
+    listener: Arc<Listener>,
+    /// Connector
+    connector: Arc<Connector>,
+
+    /// Outbound slots.
+    outbound_slots: Arc<ConnectionSlots>,
+
+    /// Resolved listen endpoint
+    listen_endpoint: Option<RwLock<Endpoint>>,
+
+    /// Holds the configuration for the P2P network.
+    config: Arc<Config>,
+
+    /// Responsible for network and system monitoring.
+    monitor: Arc<Monitor>,
+}
+
+impl LookupService {
+    /// Creates a new lookup service
+    pub fn new(
+        id: &PeerID,
+        table: Arc<Mutex<RoutingTable>>,
+        config: Arc<Config>,
+        monitor: Arc<Monitor>,
+    ) -> Self {
+        let inbound_slots = Arc::new(ConnectionSlots::new(config.lookup_inbound_slots));
+        let outbound_slots = Arc::new(ConnectionSlots::new(config.lookup_outbound_slots));
+
+        let listener = Listener::new(inbound_slots.clone(), monitor.clone());
+        let connector = Connector::new(
+            config.lookup_connect_retries,
+            outbound_slots.clone(),
+            monitor.clone(),
+        );
+
+        let listen_endpoint = config
+            .listen_endpoint
+            .as_ref()
+            .map(|endpoint| RwLock::new(endpoint.clone()));
+
+        Self {
+            id: id.clone(),
+            table,
+            listener,
+            connector,
+            outbound_slots,
+            listen_endpoint,
+            config,
+            monitor,
+        }
+    }
+
+    /// Start the lookup service.
+    pub async fn start(self: &Arc<Self>, ex: Executor<'_>) -> Result<()> {
+        self.start_listener(ex).await?;
+        Ok(())
+    }
+
+    /// Set the resolved listen endpoint.
+    pub async fn set_listen_endpoint(&self, resolved_endpoint: &Endpoint) {
+        if let Some(endpoint) = &self.listen_endpoint {
+            *endpoint.write().await = resolved_endpoint.clone();
+        }
+    }
+
+    /// Shuts down the lookup service.
+    pub async fn shutdown(&self) {
+        self.connector.shutdown().await;
+        self.listener.shutdown().await;
+    }
+
+    /// Starts iterative lookup and populate the routing table.
+    ///
+    /// This method begins by generating a random peer ID and connecting to the
+    /// provided endpoint. It then sends a FindPeer message containing the
+    /// randomly generated peer ID. Upon receiving peers from the initial lookup,
+    /// it starts connecting to these received peers and sends them a FindPeer
+    /// message that contains our own peer ID.
+    pub async fn start_lookup(&self, endpoint: &Endpoint) -> Result<()> {
+        trace!("Lookup started {endpoint}");
+        self.monitor
+            .notify(&DiscoveryEvent::LookupStarted(endpoint.clone()).into())
+            .await;
+
+        let mut random_peers = vec![];
+        if let Err(err) = self.random_lookup(endpoint, &mut random_peers).await {
+            self.monitor
+                .notify(&DiscoveryEvent::LookupFailed(endpoint.clone()).into())
+                .await;
+            return Err(err);
+        };
+
+        let mut peer_buffer = vec![];
+        self.self_lookup(&random_peers, &mut peer_buffer).await;
+
+        while peer_buffer.len() < MAX_PEERS_IN_PEERSMSG {
+            match random_peers.pop() {
+                Some(p) => peer_buffer.push(p),
+                None => break,
+            }
+        }
+
+        for peer in peer_buffer.iter() {
+            let mut table = self.table.lock().await;
+            let result = table.add_entry(peer.clone().into());
+            trace!("Add entry {:?}", result);
+        }
+
+        self.monitor
+            .notify(&DiscoveryEvent::LookupSucceeded(endpoint.clone(), peer_buffer.len()).into())
+            .await;
+
+        Ok(())
+    }
+
+    /// Starts a random lookup
+    ///
+    /// This will perfom lookup on a random generated PeerID
+    async fn random_lookup(
+        &self,
+        endpoint: &Endpoint,
+        random_peers: &mut Vec<PeerMsg>,
+    ) -> Result<()> {
+        for _ in 0..2 {
+            let peer_id = PeerID::random();
+            let peers = self.connect(&peer_id, endpoint.clone()).await?;
+            for peer in peers {
+                if random_peers.contains(&peer)
+                    || peer.peer_id == self.id
+                    || self.table.lock().await.contains_key(&peer.peer_id.0)
+                {
+                    continue;
+                }
+
+                random_peers.push(peer);
+            }
+        }
+
+        Ok(())
+    }
+
+    /// Starts a self lookup
+    async fn self_lookup(&self, random_peers: &Vec<PeerMsg>, peer_buffer: &mut Vec<PeerMsg>) {
+        let mut tasks = FuturesUnordered::new();
+        for peer in random_peers.choose_multiple(&mut OsRng, random_peers.len()) {
+            let endpoint = Endpoint::Tcp(peer.addr.clone(), peer.discovery_port);
+            tasks.push(self.connect(&self.id, endpoint))
+        }
+
+        while let Some(result) = tasks.next().await {
+            match result {
+                Ok(peers) => peer_buffer.extend(peers),
+                Err(err) => {
+                    error!("Failed to do self lookup: {err}");
+                }
+            }
+        }
+    }
+
+    /// Connects to the given endpoint
+    async fn connect(&self, peer_id: &PeerID, endpoint: Endpoint) -> Result<Vec<PeerMsg>> {
+        let conn = self.connector.connect(&endpoint).await?;
+        let io_codec = IOCodec::new(conn);
+        let result = self.handle_outbound(io_codec, peer_id).await;
+
+        self.monitor
+            .notify(&ConnEvent::Disconnected(endpoint).into())
+            .await;
+        self.outbound_slots.remove().await;
+
+        result
+    }
+
+    /// Handles outbound connection
+    async fn handle_outbound(&self, io_codec: IOCodec, peer_id: &PeerID) -> Result<Vec<PeerMsg>> {
+        trace!("Send Ping msg");
+        self.send_ping_msg(&io_codec).await?;
+
+        trace!("Send FindPeer msg");
+        let peers = self.send_findpeer_msg(&io_codec, peer_id).await?;
+
+        if peers.0.len() >= MAX_PEERS_IN_PEERSMSG {
+            return Err(Error::Lookup("Received too many peers in PeersMsg"));
+        }
+
+        trace!("Send Peer msg");
+        if let Some(endpoint) = &self.listen_endpoint {
+            self.send_peer_msg(&io_codec, endpoint.read().await.clone())
+                .await?;
+        }
+
+        trace!("Send Shutdown msg");
+        self.send_shutdown_msg(&io_codec).await?;
+
+        Ok(peers.0)
+    }
+
+    /// Start a listener.
+    async fn start_listener(self: &Arc<Self>, ex: Executor<'_>) -> Result<()> {
+        let addr = match &self.listen_endpoint {
+            Some(a) => a.read().await.addr()?.clone(),
+            None => return Ok(()),
+        };
+
+        let endpoint = Endpoint::Tcp(addr, self.config.discovery_port);
+
+        let selfc = self.clone();
+        let callback = |conn: Conn| async move {
+            let t = Duration::from_secs(selfc.config.lookup_connection_lifespan);
+            timeout(t, selfc.handle_inbound(conn)).await??;
+            Ok(())
+        };
+
+        self.listener.start(ex, endpoint.clone(), callback).await?;
+        Ok(())
+    }
+
+    /// Handles inbound connection
+    async fn handle_inbound(self: &Arc<Self>, conn: Conn) -> Result<()> {
+        let io_codec = IOCodec::new(conn);
+        loop {
+            let msg: NetMsg = io_codec.read().await?;
+            trace!("Receive msg {:?}", msg.header.command);
+
+            if let NetMsgCmd::Shutdown = msg.header.command {
+                return Ok(());
+            }
+
+            match &msg.header.command {
+                NetMsgCmd::Ping => {
+                    let (ping_msg, _) = decode::<PingMsg>(&msg.payload)?;
+                    if !version_match(&self.config.version.req, &ping_msg.version) {
+                        return Err(Error::IncompatibleVersion("system: {}".into()));
+                    }
+                    self.send_pong_msg(ping_msg.nonce, &io_codec).await?;
+                }
+                NetMsgCmd::FindPeer => {
+                    let (findpeer_msg, _) = decode::<FindPeerMsg>(&msg.payload)?;
+                    let peer_id = findpeer_msg.0;
+                    self.send_peers_msg(&peer_id, &io_codec).await?;
+                }
+                NetMsgCmd::Peer => {
+                    let (peer, _) = decode::<PeerMsg>(&msg.payload)?;
+                    let result = self.table.lock().await.add_entry(peer.clone().into());
+                    trace!("Add entry result: {:?}", result);
+                }
+                c => return Err(Error::InvalidMsg(format!("Unexpected msg: {:?}", c))),
+            }
+        }
+    }
+
+    /// Sends a Ping msg and wait to receive the Pong message.
+    async fn send_ping_msg(&self, io_codec: &IOCodec) -> Result<()> {
+        trace!("Send Pong msg");
+
+        let mut nonce: [u8; 32] = [0; 32];
+        RngCore::fill_bytes(&mut OsRng, &mut nonce);
+
+        let ping_msg = PingMsg {
+            version: self.config.version.v.clone(),
+            nonce,
+        };
+        io_codec.write(NetMsgCmd::Ping, &ping_msg).await?;
+
+        let t = Duration::from_secs(self.config.lookup_response_timeout);
+        let recv_msg: NetMsg = io_codec.read_timeout(t).await?;
+
+        let payload = get_msg_payload!(Pong, recv_msg);
+        let (pong_msg, _) = decode::<PongMsg>(&payload)?;
+
+        if ping_msg.nonce != pong_msg.0 {
+            return Err(Error::InvalidPongMsg);
+        }
+
+        Ok(())
+    }
+
+    /// Sends a Pong msg
+    async fn send_pong_msg(&self, nonce: [u8; 32], io_codec: &IOCodec) -> Result<()> {
+        trace!("Send Pong msg");
+        io_codec.write(NetMsgCmd::Pong, &PongMsg(nonce)).await?;
+        Ok(())
+    }
+
+    /// Sends a FindPeer msg and wait to receivet the Peers msg.
+    async fn send_findpeer_msg(&self, io_codec: &IOCodec, peer_id: &PeerID) -> Result<PeersMsg> {
+        trace!("Send FindPeer msg");
+        io_codec
+            .write(NetMsgCmd::FindPeer, &FindPeerMsg(peer_id.clone()))
+            .await?;
+
+        let t = Duration::from_secs(self.config.lookup_response_timeout);
+        let recv_msg: NetMsg = io_codec.read_timeout(t).await?;
+
+        let payload = get_msg_payload!(Peers, recv_msg);
+        let (peers, _) = decode(&payload)?;
+
+        Ok(peers)
+    }
+
+    /// Sends a Peers msg.
+    async fn send_peers_msg(&self, peer_id: &PeerID, io_codec: &IOCodec) -> Result<()> {
+        trace!("Send Peers msg");
+        let table = self.table.lock().await;
+        let entries = table.closest_entries(&peer_id.0, MAX_PEERS_IN_PEERSMSG);
+        let peers: Vec<PeerMsg> = entries.into_iter().map(|e| e.into()).collect();
+        drop(table);
+        io_codec.write(NetMsgCmd::Peers, &PeersMsg(peers)).await?;
+        Ok(())
+    }
+
+    /// Sends a Peer msg.
+    async fn send_peer_msg(&self, io_codec: &IOCodec, endpoint: Endpoint) -> Result<()> {
+        trace!("Send Peer msg");
+        let peer_msg = PeerMsg {
+            addr: endpoint.addr()?.clone(),
+            port: *endpoint.port()?,
+            discovery_port: self.config.discovery_port,
+            peer_id: self.id.clone(),
+        };
+        io_codec.write(NetMsgCmd::Peer, &peer_msg).await?;
+        Ok(())
+    }
+
+    /// Sends a Shutdown msg.
+    async fn send_shutdown_msg(&self, io_codec: &IOCodec) -> Result<()> {
+        trace!("Send Shutdown msg");
+        io_codec.write(NetMsgCmd::Shutdown, &ShutdownMsg(0)).await?;
+        Ok(())
+    }
+}
diff --git a/p2p/src/discovery/mod.rs b/p2p/src/discovery/mod.rs
new file mode 100644
index 0000000..94b350b
--- /dev/null
+++ b/p2p/src/discovery/mod.rs
@@ -0,0 +1,262 @@
+mod lookup;
+mod refresh;
+
+use std::sync::Arc;
+
+use log::{error, info};
+use rand::{rngs::OsRng, seq::SliceRandom};
+use smol::lock::Mutex;
+
+use karyons_core::{
+    async_utils::{Backoff, TaskGroup, TaskResult},
+    Executor,
+};
+
+use karyons_net::{Conn, Endpoint};
+
+use crate::{
+    config::Config,
+    monitor::Monitor,
+    net::ConnQueue,
+    net::{ConnDirection, ConnectionSlots, Connector, Listener},
+    routing_table::{
+        Entry, EntryStatusFlag, RoutingTable, CONNECTED_ENTRY, DISCONNECTED_ENTRY, PENDING_ENTRY,
+        UNREACHABLE_ENTRY, UNSTABLE_ENTRY,
+    },
+    Error, PeerID, Result,
+};
+
+use lookup::LookupService;
+use refresh::RefreshService;
+
+pub type ArcDiscovery = Arc<Discovery>;
+
+pub struct Discovery {
+    /// Routing table
+    table: Arc<Mutex<RoutingTable>>,
+
+    /// Lookup Service
+    lookup_service: Arc<LookupService>,
+
+    /// Refresh Service
+    refresh_service: Arc<RefreshService>,
+
+    /// Connector
+    connector: Arc<Connector>,
+    /// Listener
+    listener: Arc<Listener>,
+
+    /// Connection queue
+    conn_queue: Arc<ConnQueue>,
+
+    /// Inbound slots.
+    pub(crate) inbound_slots: Arc<ConnectionSlots>,
+    /// Outbound slots.
+    pub(crate) outbound_slots: Arc<ConnectionSlots>,
+
+    /// Managing spawned tasks.
+    task_group: TaskGroup,
+
+    /// Holds the configuration for the P2P network.
+    config: Arc<Config>,
+}
+
+impl Discovery {
+    /// Creates a new Discovery
+    pub fn new(
+        peer_id: &PeerID,
+        conn_queue: Arc<ConnQueue>,
+        config: Arc<Config>,
+        monitor: Arc<Monitor>,
+    ) -> ArcDiscovery {
+        let inbound_slots = Arc::new(ConnectionSlots::new(config.inbound_slots));
+        let outbound_slots = Arc::new(ConnectionSlots::new(config.outbound_slots));
+
+        let table_key = peer_id.0;
+        let table = Arc::new(Mutex::new(RoutingTable::new(table_key)));
+
+        let refresh_service = RefreshService::new(config.clone(), table.clone(), monitor.clone());
+        let lookup_service =
+            LookupService::new(peer_id, table.clone(), config.clone(), monitor.clone());
+
+        let connector = Connector::new(
+            config.max_connect_retries,
+            outbound_slots.clone(),
+            monitor.clone(),
+        );
+        let listener = Listener::new(inbound_slots.clone(), monitor.clone());
+
+        Arc::new(Self {
+            refresh_service: Arc::new(refresh_service),
+            lookup_service: Arc::new(lookup_service),
+            conn_queue,
+            table,
+            inbound_slots,
+            outbound_slots,
+            connector,
+            listener,
+            task_group: TaskGroup::new(),
+            config,
+        })
+    }
+
+    /// Start the Discovery
+    pub async fn start(self: &Arc<Self>, ex: Executor<'_>) -> Result<()> {
+        // Check if the listen_endpoint is provided, and if so, start a listener.
+        if let Some(endpoint) = &self.config.listen_endpoint {
+            // Return an error if the discovery port is set to 0.
+            if self.config.discovery_port == 0 {
+                return Err(Error::Config(
+                    "Please add a valid discovery port".to_string(),
+                ));
+            }
+
+            let resolved_endpoint = self.start_listener(endpoint, ex.clone()).await?;
+
+            if endpoint.addr()? != resolved_endpoint.addr()? {
+                info!("Resolved listen endpoint: {resolved_endpoint}");
+                self.lookup_service
+                    .set_listen_endpoint(&resolved_endpoint)
+                    .await;
+                self.refresh_service
+                    .set_listen_endpoint(&resolved_endpoint)
+                    .await;
+            }
+        }
+
+        // Start the lookup service
+        self.lookup_service.start(ex.clone()).await?;
+        // Start the refresh service
+        self.refresh_service.start(ex.clone()).await?;
+
+        // Attempt to manually connect to peer endpoints provided in the Config.
+        for endpoint in self.config.peer_endpoints.iter() {
+            let _ = self.connect(endpoint, None, ex.clone()).await;
+        }
+
+        // Start connect loop
+        let selfc = self.clone();
+        self.task_group
+            .spawn(ex.clone(), selfc.connect_loop(ex), |res| async move {
+                if let TaskResult::Completed(Err(err)) = res {
+                    error!("Connect loop stopped: {err}");
+                }
+            });
+
+        Ok(())
+    }
+
+    /// Shuts down the discovery
+    pub async fn shutdown(&self) {
+        self.task_group.cancel().await;
+        self.connector.shutdown().await;
+        self.listener.shutdown().await;
+
+        self.refresh_service.shutdown().await;
+        self.lookup_service.shutdown().await;
+    }
+
+    /// Start a listener and on success, return the resolved endpoint.
+    async fn start_listener(
+        self: &Arc<Self>,
+        endpoint: &Endpoint,
+        ex: Executor<'_>,
+    ) -> Result<Endpoint> {
+        let selfc = self.clone();
+        let callback = |conn: Conn| async move {
+            selfc.conn_queue.handle(conn, ConnDirection::Inbound).await;
+            Ok(())
+        };
+
+        let resolved_endpoint = self.listener.start(ex, endpoint.clone(), callback).await?;
+        Ok(resolved_endpoint)
+    }
+
+    /// This method will attempt to connect to a peer in the routing table.
+    /// If the routing table is empty, it will start the seeding process for
+    /// finding new peers.
+    ///
+    /// This will perform a backoff to prevent getting stuck in the loop
+    /// if the seeding process couldn't find any peers.
+    async fn connect_loop(self: Arc<Self>, ex: Executor<'_>) -> Result<()> {
+        let backoff = Backoff::new(500, self.config.seeding_interval * 1000);
+        loop {
+            let random_entry = self.random_entry(PENDING_ENTRY).await;
+            match random_entry {
+                Some(entry) => {
+                    backoff.reset();
+                    let endpoint = Endpoint::Tcp(entry.addr, entry.port);
+                    self.connect(&endpoint, Some(entry.key.into()), ex.clone())
+                        .await;
+                }
+                None => {
+                    backoff.sleep().await;
+                    self.start_seeding().await;
+                }
+            }
+        }
+    }
+
+    /// Connect to the given endpoint using the connector
+    async fn connect(self: &Arc<Self>, endpoint: &Endpoint, pid: Option<PeerID>, ex: Executor<'_>) {
+        let selfc = self.clone();
+        let pid_cloned = pid.clone();
+        let cback = |conn: Conn| async move {
+            selfc.conn_queue.handle(conn, ConnDirection::Outbound).await;
+            if let Some(pid) = pid_cloned {
+                selfc.update_entry(&pid, DISCONNECTED_ENTRY).await;
+            }
+            Ok(())
+        };
+
+        let res = self.connector.connect_with_cback(ex, endpoint, cback).await;
+
+        if let Some(pid) = &pid {
+            match res {
+                Ok(_) => {
+                    self.update_entry(pid, CONNECTED_ENTRY).await;
+                }
+                Err(_) => {
+                    self.update_entry(pid, UNREACHABLE_ENTRY).await;
+                }
+            }
+        }
+    }
+
+    /// Starts seeding process.
+    ///
+    /// This method randomly selects a peer from the routing table and
+    /// attempts to connect to that peer for the initial lookup. If the routing
+    /// table doesn't have an available entry, it will connect to one of the
+    /// provided bootstrap endpoints in the `Config` and initiate the lookup.
+    async fn start_seeding(&self) {
+        match self.random_entry(PENDING_ENTRY | CONNECTED_ENTRY).await {
+            Some(entry) => {
+                let endpoint = Endpoint::Tcp(entry.addr, entry.discovery_port);
+                if let Err(err) = self.lookup_service.start_lookup(&endpoint).await {
+                    self.update_entry(&entry.key.into(), UNSTABLE_ENTRY).await;
+                    error!("Failed to do lookup: {endpoint}: {err}");
+                }
+            }
+            None => {
+                let peers = &self.config.bootstrap_peers;
+                for endpoint in peers.choose_multiple(&mut OsRng, peers.len()) {
+                    if let Err(err) = self.lookup_service.start_lookup(endpoint).await {
+                        error!("Failed to do lookup: {endpoint}: {err}");
+                    }
+                }
+            }
+        }
+    }
+
+    /// Returns a random entry from routing table.
+    async fn random_entry(&self, entry_flag: EntryStatusFlag) -> Option<Entry> {
+        self.table.lock().await.random_entry(entry_flag).cloned()
+    }
+
+    /// Update the entry status  
+    async fn update_entry(&self, pid: &PeerID, entry_flag: EntryStatusFlag) {
+        let table = &mut self.table.lock().await;
+        table.update_entry(&pid.0, entry_flag);
+    }
+}
diff --git a/p2p/src/discovery/refresh.rs b/p2p/src/discovery/refresh.rs
new file mode 100644
index 0000000..7582c84
--- /dev/null
+++ b/p2p/src/discovery/refresh.rs
@@ -0,0 +1,289 @@
+use std::{sync::Arc, time::Duration};
+
+use bincode::{Decode, Encode};
+use log::{error, info, trace};
+use rand::{rngs::OsRng, RngCore};
+use smol::{
+    lock::{Mutex, RwLock},
+    stream::StreamExt,
+    Timer,
+};
+
+use karyons_core::{
+    async_utils::{timeout, Backoff, TaskGroup, TaskResult},
+    utils::{decode, encode},
+    Executor,
+};
+
+use karyons_net::{dial_udp, listen_udp, Addr, Connection, Endpoint, NetError, Port, UdpConn};
+
+/// Maximum failures for an entry before removing it from the routing table.
+pub const MAX_FAILURES: u32 = 3;
+
+/// Ping message size
+const PINGMSG_SIZE: usize = 32;
+
+use crate::{
+    monitor::{ConnEvent, DiscoveryEvent, Monitor},
+    routing_table::{BucketEntry, Entry, RoutingTable, PENDING_ENTRY, UNREACHABLE_ENTRY},
+    Config, Error, Result,
+};
+
+#[derive(Decode, Encode, Debug, Clone)]
+pub struct PingMsg(pub [u8; 32]);
+
+#[derive(Decode, Encode, Debug)]
+pub struct PongMsg(pub [u8; 32]);
+
+pub struct RefreshService {
+    /// Routing table
+    table: Arc<Mutex<RoutingTable>>,
+
+    /// Resolved listen endpoint
+    listen_endpoint: Option<RwLock<Endpoint>>,
+
+    /// Managing spawned tasks.
+    task_group: TaskGroup,
+
+    /// Holds the configuration for the P2P network.
+    config: Arc<Config>,
+
+    /// Responsible for network and system monitoring.
+    monitor: Arc<Monitor>,
+}
+
+impl RefreshService {
+    /// Creates a new refresh service
+    pub fn new(
+        config: Arc<Config>,
+        table: Arc<Mutex<RoutingTable>>,
+        monitor: Arc<Monitor>,
+    ) -> Self {
+        let listen_endpoint = config
+            .listen_endpoint
+            .as_ref()
+            .map(|endpoint| RwLock::new(endpoint.clone()));
+
+        Self {
+            table,
+            listen_endpoint,
+            task_group: TaskGroup::new(),
+            config,
+            monitor,
+        }
+    }
+
+    /// Start the refresh service
+    pub async fn start(self: &Arc<Self>, ex: Executor<'_>) -> Result<()> {
+        if let Some(endpoint) = &self.listen_endpoint {
+            let endpoint = endpoint.read().await;
+            let addr = endpoint.addr()?;
+            let port = self.config.discovery_port;
+
+            let selfc = self.clone();
+            self.task_group.spawn(
+                ex.clone(),
+                selfc.listen_loop(addr.clone(), port),
+                |res| async move {
+                    if let TaskResult::Completed(Err(err)) = res {
+                        error!("Listen loop stopped: {err}");
+                    }
+                },
+            );
+        }
+
+        let selfc = self.clone();
+        self.task_group.spawn(
+            ex.clone(),
+            selfc.refresh_loop(ex.clone()),
+            |res| async move {
+                if let TaskResult::Completed(Err(err)) = res {
+                    error!("Refresh loop stopped: {err}");
+                }
+            },
+        );
+
+        Ok(())
+    }
+
+    /// Set the resolved listen endpoint.
+    pub async fn set_listen_endpoint(&self, resolved_endpoint: &Endpoint) {
+        if let Some(endpoint) = &self.listen_endpoint {
+            *endpoint.write().await = resolved_endpoint.clone();
+        }
+    }
+
+    /// Shuts down the refresh service
+    pub async fn shutdown(&self) {
+        self.task_group.cancel().await;
+    }
+
+    /// Initiates periodic refreshing of the routing table. This function will
+    /// select 8 random entries from each bucket in the routing table and start
+    /// sending Ping messages to the entries.
+    async fn refresh_loop(self: Arc<Self>, ex: Executor<'_>) -> Result<()> {
+        let mut timer = Timer::interval(Duration::from_secs(self.config.refresh_interval));
+        loop {
+            timer.next().await;
+            trace!("Start refreshing the routing table...");
+
+            self.monitor
+                .notify(&DiscoveryEvent::RefreshStarted.into())
+                .await;
+
+            let table = self.table.lock().await;
+            let mut entries: Vec<BucketEntry> = vec![];
+            for bucket in table.iter() {
+                for entry in bucket.random_iter(8) {
+                    entries.push(entry.clone())
+                }
+            }
+            drop(table);
+
+            self.clone().do_refresh(&entries, ex.clone()).await;
+        }
+    }
+
+    /// Iterates over the entries and spawns a new task for each entry to
+    /// initiate a connection attempt to that entry.
+    async fn do_refresh(self: Arc<Self>, entries: &[BucketEntry], ex: Executor<'_>) {
+        for chunk in entries.chunks(16) {
+            let mut tasks = Vec::new();
+            for bucket_entry in chunk {
+                if bucket_entry.is_connected() {
+                    continue;
+                }
+
+                if bucket_entry.failures >= MAX_FAILURES {
+                    self.table
+                        .lock()
+                        .await
+                        .remove_entry(&bucket_entry.entry.key);
+                    return;
+                }
+
+                tasks.push(ex.spawn(self.clone().refresh_entry(bucket_entry.clone())))
+            }
+
+            for task in tasks {
+                task.await;
+            }
+        }
+    }
+
+    /// Initiates refresh for a specific entry within the routing table. It
+    /// updates the routing table according to the result.
+    async fn refresh_entry(self: Arc<Self>, bucket_entry: BucketEntry) {
+        let key = &bucket_entry.entry.key;
+        match self.connect(&bucket_entry.entry).await {
+            Ok(_) => {
+                self.table.lock().await.update_entry(key, PENDING_ENTRY);
+            }
+            Err(err) => {
+                trace!("Failed to refresh entry {:?}: {err}", key);
+                let table = &mut self.table.lock().await;
+                if bucket_entry.failures >= MAX_FAILURES {
+                    table.remove_entry(key);
+                    return;
+                }
+                table.update_entry(key, UNREACHABLE_ENTRY);
+            }
+        }
+    }
+
+    /// Initiates a UDP connection with the entry and attempts to send a Ping
+    /// message. If it fails, it retries according to the allowed retries
+    /// specified in the Config, with backoff between each retry.
+    async fn connect(&self, entry: &Entry) -> Result<()> {
+        let mut retry = 0;
+        let conn = dial_udp(&entry.addr, &entry.discovery_port).await?;
+        let backoff = Backoff::new(100, 5000);
+        while retry < self.config.refresh_connect_retries {
+            match self.send_ping_msg(&conn).await {
+                Ok(()) => return Ok(()),
+                Err(Error::KaryonsNet(NetError::Timeout)) => {
+                    retry += 1;
+                    backoff.sleep().await;
+                }
+                Err(err) => {
+                    return Err(err);
+                }
+            }
+        }
+
+        Err(NetError::Timeout.into())
+    }
+
+    /// Set up a UDP listener and start listening for Ping messages from other
+    /// peers.
+    async fn listen_loop(self: Arc<Self>, addr: Addr, port: Port) -> Result<()> {
+        let endpoint = Endpoint::Udp(addr.clone(), port);
+        let conn = match listen_udp(&addr, &port).await {
+            Ok(c) => {
+                self.monitor
+                    .notify(&ConnEvent::Listening(endpoint.clone()).into())
+                    .await;
+                c
+            }
+            Err(err) => {
+                self.monitor
+                    .notify(&ConnEvent::ListenFailed(endpoint.clone()).into())
+                    .await;
+                return Err(err.into());
+            }
+        };
+        info!("Start listening on {endpoint}");
+
+        loop {
+            let res = self.listen_to_ping_msg(&conn).await;
+            if let Err(err) = res {
+                trace!("Failed to handle ping msg {err}");
+                self.monitor.notify(&ConnEvent::AcceptFailed.into()).await;
+            }
+        }
+    }
+
+    /// Listen to receive a Ping message and respond with a Pong message.
+    async fn listen_to_ping_msg(&self, conn: &UdpConn) -> Result<()> {
+        let mut buf = [0; PINGMSG_SIZE];
+        let (_, endpoint) = conn.recv_from(&mut buf).await?;
+
+        self.monitor
+            .notify(&ConnEvent::Accepted(endpoint.clone()).into())
+            .await;
+
+        let (ping_msg, _) = decode::<PingMsg>(&buf)?;
+
+        let pong_msg = PongMsg(ping_msg.0);
+        let buffer = encode(&pong_msg)?;
+
+        conn.send_to(&buffer, &endpoint).await?;
+
+        self.monitor
+            .notify(&ConnEvent::Disconnected(endpoint.clone()).into())
+            .await;
+        Ok(())
+    }
+
+    /// Sends a Ping msg and wait to receive the Pong message.
+    async fn send_ping_msg(&self, conn: &UdpConn) -> Result<()> {
+        let mut nonce: [u8; 32] = [0; 32];
+        RngCore::fill_bytes(&mut OsRng, &mut nonce);
+
+        let ping_msg = PingMsg(nonce);
+        let buffer = encode(&ping_msg)?;
+        conn.send(&buffer).await?;
+
+        let buf = &mut [0; PINGMSG_SIZE];
+        let t = Duration::from_secs(self.config.refresh_response_timeout);
+        timeout(t, conn.recv(buf)).await??;
+
+        let (pong_msg, _) = decode::<PongMsg>(buf)?;
+
+        if ping_msg.0 != pong_msg.0 {
+            return Err(Error::InvalidPongMsg);
+        }
+
+        Ok(())
+    }
+}
diff --git a/p2p/src/error.rs b/p2p/src/error.rs
new file mode 100644
index 0000000..945e90a
--- /dev/null
+++ b/p2p/src/error.rs
@@ -0,0 +1,82 @@
+use thiserror::Error as ThisError;
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+/// Represents Karyons's p2p Error.
+#[derive(ThisError, Debug)]
+pub enum Error {
+    #[error("IO Error: {0}")]
+    IO(#[from] std::io::Error),
+
+    #[error("Unsupported protocol error: {0}")]
+    UnsupportedProtocol(String),
+
+    #[error("Invalid message error: {0}")]
+    InvalidMsg(String),
+
+    #[error("Parse error: {0}")]
+    ParseError(String),
+
+    #[error("Incompatible version error: {0}")]
+    IncompatibleVersion(String),
+
+    #[error("Config error: {0}")]
+    Config(String),
+
+    #[error("Peer shutdown")]
+    PeerShutdown,
+
+    #[error("Invalid Pong Msg")]
+    InvalidPongMsg,
+
+    #[error("Discovery error: {0}")]
+    Discovery(&'static str),
+
+    #[error("Lookup error: {0}")]
+    Lookup(&'static str),
+
+    #[error("Peer already connected")]
+    PeerAlreadyConnected,
+
+    #[error("Channel Send Error: {0}")]
+    ChannelSend(String),
+
+    #[error("Channel Receive Error: {0}")]
+    ChannelRecv(String),
+
+    #[error("CORE::ERROR : {0}")]
+    KaryonsCore(#[from] karyons_core::error::Error),
+
+    #[error("NET::ERROR : {0}")]
+    KaryonsNet(#[from] karyons_net::NetError),
+}
+
+impl<T> From<smol::channel::SendError<T>> for Error {
+    fn from(error: smol::channel::SendError<T>) -> Self {
+        Error::ChannelSend(error.to_string())
+    }
+}
+
+impl From<smol::channel::RecvError> for Error {
+    fn from(error: smol::channel::RecvError) -> Self {
+        Error::ChannelRecv(error.to_string())
+    }
+}
+
+impl From<std::num::ParseIntError> for Error {
+    fn from(error: std::num::ParseIntError) -> Self {
+        Error::ParseError(error.to_string())
+    }
+}
+
+impl From<std::num::ParseFloatError> for Error {
+    fn from(error: std::num::ParseFloatError) -> Self {
+        Error::ParseError(error.to_string())
+    }
+}
+
+impl From<semver::Error> for Error {
+    fn from(error: semver::Error) -> Self {
+        Error::ParseError(error.to_string())
+    }
+}
diff --git a/p2p/src/io_codec.rs b/p2p/src/io_codec.rs
new file mode 100644
index 0000000..4515832
--- /dev/null
+++ b/p2p/src/io_codec.rs
@@ -0,0 +1,102 @@
+use std::time::Duration;
+
+use bincode::{Decode, Encode};
+
+use karyons_core::{
+    async_utils::timeout,
+    utils::{decode, encode, encode_into_slice},
+};
+
+use karyons_net::{Connection, NetError};
+
+use crate::{
+    message::{NetMsg, NetMsgCmd, NetMsgHeader, MAX_ALLOWED_MSG_SIZE, MSG_HEADER_SIZE},
+    Error, Result,
+};
+
+pub trait CodecMsg: Decode + Encode + std::fmt::Debug {}
+impl<T: Encode + Decode + std::fmt::Debug> CodecMsg for T {}
+
+/// I/O codec working with generic network connections.
+///
+/// It is responsible for both decoding data received from the network and
+/// encoding data before sending it.
+pub struct IOCodec {
+    conn: Box<dyn Connection>,
+}
+
+impl IOCodec {
+    /// Creates a new IOCodec.
+    pub fn new(conn: Box<dyn Connection>) -> Self {
+        Self { conn }
+    }
+
+    /// Reads a message of type `NetMsg` from the connection.
+    ///
+    /// It reads the first 6 bytes as the header of the message, then reads
+    /// and decodes the remaining message data based on the determined header.
+    pub async fn read(&self) -> Result<NetMsg> {
+        // Read 6 bytes to get the header of the incoming message
+        let mut buf = [0; MSG_HEADER_SIZE];
+        self.conn.recv(&mut buf).await?;
+
+        // Decode the header from bytes to NetMsgHeader
+        let (header, _) = decode::<NetMsgHeader>(&buf)?;
+
+        if header.payload_size > MAX_ALLOWED_MSG_SIZE {
+            return Err(Error::InvalidMsg(
+                "Message exceeds the maximum allowed size".to_string(),
+            ));
+        }
+
+        // Create a buffer to hold the message based on its length
+        let mut payload = vec![0; header.payload_size as usize];
+        self.conn.recv(&mut payload).await?;
+
+        Ok(NetMsg { header, payload })
+    }
+
+    /// Writes a message of type `T` to the connection.
+    ///
+    /// Before appending the actual message payload, it calculates the length of
+    /// the encoded message in bytes and appends this length to the message header.
+    pub async fn write<T: CodecMsg>(&self, command: NetMsgCmd, msg: &T) -> Result<()> {
+        let payload = encode(msg)?;
+
+        // Create a buffer to hold the message header (6 bytes)
+        let header_buf = &mut [0; MSG_HEADER_SIZE];
+        let header = NetMsgHeader {
+            command,
+            payload_size: payload.len() as u32,
+        };
+        encode_into_slice(&header, header_buf)?;
+
+        let mut buffer = vec![];
+        // Append the header bytes to the buffer
+        buffer.extend_from_slice(header_buf);
+        // Append the message payload to the buffer
+        buffer.extend_from_slice(&payload);
+
+        self.conn.send(&buffer).await?;
+        Ok(())
+    }
+
+    /// Reads a message of type `NetMsg` with the given timeout.
+    pub async fn read_timeout(&self, duration: Duration) -> Result<NetMsg> {
+        timeout(duration, self.read())
+            .await
+            .map_err(|_| NetError::Timeout)?
+    }
+
+    /// Writes a message of type `T` with the given timeout.
+    pub async fn write_timeout<T: CodecMsg>(
+        &self,
+        command: NetMsgCmd,
+        msg: &T,
+        duration: Duration,
+    ) -> Result<()> {
+        timeout(duration, self.write(command, msg))
+            .await
+            .map_err(|_| NetError::Timeout)?
+    }
+}
diff --git a/p2p/src/lib.rs b/p2p/src/lib.rs
new file mode 100644
index 0000000..08ba059
--- /dev/null
+++ b/p2p/src/lib.rs
@@ -0,0 +1,27 @@
+mod backend;
+mod config;
+mod discovery;
+mod error;
+mod io_codec;
+mod message;
+mod net;
+mod peer;
+mod peer_pool;
+mod protocols;
+mod routing_table;
+mod utils;
+
+/// Responsible for network and system monitoring.
+/// [`Read More`](./monitor/struct.Monitor.html)
+pub mod monitor;
+/// Defines the protocol trait.
+/// [`Read More`](./protocol/trait.Protocol.html)
+pub mod protocol;
+
+pub use backend::{ArcBackend, Backend};
+pub use config::Config;
+pub use error::Error as P2pError;
+pub use peer::{ArcPeer, PeerID};
+pub use utils::Version;
+
+use error::{Error, Result};
diff --git a/p2p/src/message.rs b/p2p/src/message.rs
new file mode 100644
index 0000000..833f6f4
--- /dev/null
+++ b/p2p/src/message.rs
@@ -0,0 +1,133 @@
+use std::collections::HashMap;
+
+use bincode::{Decode, Encode};
+
+use karyons_net::{Addr, Port};
+
+use crate::{protocol::ProtocolID, routing_table::Entry, utils::VersionInt, PeerID};
+
+/// The size of the message header, in bytes.
+pub const MSG_HEADER_SIZE: usize = 6;
+
+/// The maximum allowed size for a message in bytes.
+pub const MAX_ALLOWED_MSG_SIZE: u32 = 1000000;
+
+/// Defines the main message in the Karyon P2P network.
+///
+/// This message structure consists of a header and payload, where the header
+/// typically contains essential information about the message, and the payload
+/// contains the actual data being transmitted.
+#[derive(Decode, Encode, Debug, Clone)]
+pub struct NetMsg {
+    pub header: NetMsgHeader,
+    pub payload: Vec<u8>,
+}
+
+/// Represents the header of a message.
+#[derive(Decode, Encode, Debug, Clone)]
+pub struct NetMsgHeader {
+    pub command: NetMsgCmd,
+    pub payload_size: u32,
+}
+
+/// Defines message commands.
+#[derive(Decode, Encode, Debug, Clone)]
+#[repr(u8)]
+pub enum NetMsgCmd {
+    Version,
+    Verack,
+    Protocol,
+    Shutdown,
+
+    // NOTE: The following commands are used during the lookup process.
+    Ping,
+    Pong,
+    FindPeer,
+    Peer,
+    Peers,
+}
+
+/// Defines a message related to a specific protocol.
+#[derive(Decode, Encode, Debug, Clone)]
+pub struct ProtocolMsg {
+    pub protocol_id: ProtocolID,
+    pub payload: Vec<u8>,
+}
+
+/// Version message, providing information about a peer's capabilities.
+#[derive(Decode, Encode, Debug, Clone)]
+pub struct VerMsg {
+    pub peer_id: PeerID,
+    pub version: VersionInt,
+    pub protocols: HashMap<ProtocolID, VersionInt>,
+}
+
+/// VerAck message acknowledging the receipt of a Version message.
+#[derive(Decode, Encode, Debug, Clone)]
+pub struct VerAckMsg(pub PeerID);
+
+/// Shutdown message.
+#[derive(Decode, Encode, Debug, Clone)]
+pub struct ShutdownMsg(pub u8);
+
+/// Ping message with a nonce and version information.
+#[derive(Decode, Encode, Debug, Clone)]
+pub struct PingMsg {
+    pub nonce: [u8; 32],
+    pub version: VersionInt,
+}
+
+/// Ping message with a nonce.
+#[derive(Decode, Encode, Debug)]
+pub struct PongMsg(pub [u8; 32]);
+
+/// FindPeer message used to find a specific peer.
+#[derive(Decode, Encode, Debug)]
+pub struct FindPeerMsg(pub PeerID);
+
+/// PeerMsg containing information about a peer.
+#[derive(Decode, Encode, Debug, Clone, PartialEq, Eq)]
+pub struct PeerMsg {
+    pub peer_id: PeerID,
+    pub addr: Addr,
+    pub port: Port,
+    pub discovery_port: Port,
+}
+
+/// PeersMsg a list of `PeerMsg`.
+#[derive(Decode, Encode, Debug)]
+pub struct PeersMsg(pub Vec<PeerMsg>);
+
+macro_rules! get_msg_payload {
+    ($a:ident, $b:expr) => {
+        if let NetMsgCmd::$a = $b.header.command {
+            $b.payload
+        } else {
+            return Err(Error::InvalidMsg(format!("Unexpected msg{:?}", $b)));
+        }
+    };
+}
+
+pub(super) use get_msg_payload;
+
+impl From<Entry> for PeerMsg {
+    fn from(entry: Entry) -> PeerMsg {
+        PeerMsg {
+            peer_id: PeerID(entry.key),
+            addr: entry.addr,
+            port: entry.port,
+            discovery_port: entry.discovery_port,
+        }
+    }
+}
+
+impl From<PeerMsg> for Entry {
+    fn from(peer: PeerMsg) -> Entry {
+        Entry {
+            key: peer.peer_id.0,
+            addr: peer.addr,
+            port: peer.port,
+            discovery_port: peer.discovery_port,
+        }
+    }
+}
diff --git a/p2p/src/monitor.rs b/p2p/src/monitor.rs
new file mode 100644
index 0000000..ee0bf44
--- /dev/null
+++ b/p2p/src/monitor.rs
@@ -0,0 +1,154 @@
+use std::fmt;
+
+use crate::PeerID;
+
+use karyons_core::pubsub::{ArcPublisher, Publisher, Subscription};
+
+use karyons_net::Endpoint;
+
+/// Responsible for network and system monitoring.
+///
+/// It use pub-sub pattern to notify the subscribers with new events.
+///
+/// # Example
+///
+/// ```
+/// use karyons_p2p::{Config, Backend, PeerID};
+/// async {
+///     
+///     let backend = Backend::new(PeerID::random(), Config::default());
+///     
+///     // Create a new Subscription
+///     let sub =  backend.monitor().await;
+///     
+///     let event = sub.recv().await;
+/// };
+/// ```
+pub struct Monitor {
+    inner: ArcPublisher<MonitorEvent>,
+}
+
+impl Monitor {
+    /// Creates a new Monitor
+    pub(crate) fn new() -> Monitor {
+        Self {
+            inner: Publisher::new(),
+        }
+    }
+
+    /// Sends a new monitor event to all subscribers.
+    pub async fn notify(&self, event: &MonitorEvent) {
+        self.inner.notify(event).await;
+    }
+
+    /// Subscribes to listen to new events.
+    pub async fn subscribe(&self) -> Subscription<MonitorEvent> {
+        self.inner.subscribe().await
+    }
+}
+
+/// Defines various type of event that can be monitored.
+#[derive(Clone, Debug)]
+pub enum MonitorEvent {
+    Conn(ConnEvent),
+    PeerPool(PeerPoolEvent),
+    Discovery(DiscoveryEvent),
+}
+
+/// Defines connection-related events.
+#[derive(Clone, Debug)]
+pub enum ConnEvent {
+    Connected(Endpoint),
+    ConnectRetried(Endpoint),
+    ConnectFailed(Endpoint),
+    Accepted(Endpoint),
+    AcceptFailed,
+    Disconnected(Endpoint),
+    Listening(Endpoint),
+    ListenFailed(Endpoint),
+}
+
+/// Defines `PeerPool` events.
+#[derive(Clone, Debug)]
+pub enum PeerPoolEvent {
+    NewPeer(PeerID),
+    RemovePeer(PeerID),
+}
+
+/// Defines `Discovery` events.
+#[derive(Clone, Debug)]
+pub enum DiscoveryEvent {
+    LookupStarted(Endpoint),
+    LookupFailed(Endpoint),
+    LookupSucceeded(Endpoint, usize),
+    RefreshStarted,
+}
+
+impl fmt::Display for MonitorEvent {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let val = match self {
+            MonitorEvent::Conn(e) => format!("Connection Event: {e}"),
+            MonitorEvent::PeerPool(e) => format!("PeerPool Event: {e}"),
+            MonitorEvent::Discovery(e) => format!("Discovery Event: {e}"),
+        };
+        write!(f, "{}", val)
+    }
+}
+
+impl fmt::Display for ConnEvent {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let val = match self {
+            ConnEvent::Connected(endpoint) => format!("Connected: {endpoint}"),
+            ConnEvent::ConnectFailed(endpoint) => format!("ConnectFailed: {endpoint}"),
+            ConnEvent::ConnectRetried(endpoint) => format!("ConnectRetried: {endpoint}"),
+            ConnEvent::AcceptFailed => "AcceptFailed".to_string(),
+            ConnEvent::Accepted(endpoint) => format!("Accepted: {endpoint}"),
+            ConnEvent::Disconnected(endpoint) => format!("Disconnected: {endpoint}"),
+            ConnEvent::Listening(endpoint) => format!("Listening: {endpoint}"),
+            ConnEvent::ListenFailed(endpoint) => format!("ListenFailed: {endpoint}"),
+        };
+        write!(f, "{}", val)
+    }
+}
+
+impl fmt::Display for PeerPoolEvent {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let val = match self {
+            PeerPoolEvent::NewPeer(pid) => format!("NewPeer: {pid}"),
+            PeerPoolEvent::RemovePeer(pid) => format!("RemovePeer: {pid}"),
+        };
+        write!(f, "{}", val)
+    }
+}
+
+impl fmt::Display for DiscoveryEvent {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let val = match self {
+            DiscoveryEvent::LookupStarted(endpoint) => format!("LookupStarted: {endpoint}"),
+            DiscoveryEvent::LookupFailed(endpoint) => format!("LookupFailed: {endpoint}"),
+            DiscoveryEvent::LookupSucceeded(endpoint, len) => {
+                format!("LookupSucceeded: {endpoint} {len}")
+            }
+            DiscoveryEvent::RefreshStarted => "RefreshStarted".to_string(),
+        };
+        write!(f, "{}", val)
+    }
+}
+
+impl From<ConnEvent> for MonitorEvent {
+    fn from(val: ConnEvent) -> Self {
+        MonitorEvent::Conn(val)
+    }
+}
+
+impl From<PeerPoolEvent> for MonitorEvent {
+    fn from(val: PeerPoolEvent) -> Self {
+        MonitorEvent::PeerPool(val)
+    }
+}
+
+impl From<DiscoveryEvent> for MonitorEvent {
+    fn from(val: DiscoveryEvent) -> Self {
+        MonitorEvent::Discovery(val)
+    }
+}
diff --git a/p2p/src/net/connection_queue.rs b/p2p/src/net/connection_queue.rs
new file mode 100644
index 0000000..fbc4bfc
--- /dev/null
+++ b/p2p/src/net/connection_queue.rs
@@ -0,0 +1,52 @@
+use std::sync::Arc;
+
+use smol::{channel::Sender, lock::Mutex};
+
+use karyons_core::async_utils::CondVar;
+
+use karyons_net::Conn;
+
+use crate::net::ConnDirection;
+
+pub struct NewConn {
+    pub direction: ConnDirection,
+    pub conn: Conn,
+    pub disconnect_signal: Sender<()>,
+}
+
+/// Connection queue
+pub struct ConnQueue {
+    queue: Mutex<Vec<NewConn>>,
+    conn_available: CondVar,
+}
+
+impl ConnQueue {
+    pub fn new() -> Arc<Self> {
+        Arc::new(Self {
+            queue: Mutex::new(Vec::new()),
+            conn_available: CondVar::new(),
+        })
+    }
+
+    /// Push a connection into the queue and wait for the disconnect signal
+    pub async fn handle(&self, conn: Conn, direction: ConnDirection) {
+        let (disconnect_signal, chan) = smol::channel::bounded(1);
+        let new_conn = NewConn {
+            direction,
+            conn,
+            disconnect_signal,
+        };
+        self.queue.lock().await.push(new_conn);
+        self.conn_available.signal();
+        let _ = chan.recv().await;
+    }
+
+    /// Receive the next connection in the queue
+    pub async fn next(&self) -> NewConn {
+        let mut queue = self.queue.lock().await;
+        while queue.is_empty() {
+            queue = self.conn_available.wait(queue).await;
+        }
+        queue.pop().unwrap()
+    }
+}
diff --git a/p2p/src/net/connector.rs b/p2p/src/net/connector.rs
new file mode 100644
index 0000000..72dc0d8
--- /dev/null
+++ b/p2p/src/net/connector.rs
@@ -0,0 +1,125 @@
+use std::{future::Future, sync::Arc};
+
+use log::{trace, warn};
+
+use karyons_core::{
+    async_utils::{Backoff, TaskGroup, TaskResult},
+    Executor,
+};
+use karyons_net::{dial, Conn, Endpoint, NetError};
+
+use crate::{
+    monitor::{ConnEvent, Monitor},
+    Result,
+};
+
+use super::slots::ConnectionSlots;
+
+/// Responsible for creating outbound connections with other peers.
+pub struct Connector {
+    /// Managing spawned tasks.
+    task_group: TaskGroup,
+
+    /// Manages available outbound slots.
+    connection_slots: Arc<ConnectionSlots>,
+
+    /// The maximum number of retries allowed before successfully
+    /// establishing a connection.
+    max_retries: usize,
+
+    /// Responsible for network and system monitoring.
+    monitor: Arc<Monitor>,
+}
+
+impl Connector {
+    /// Creates a new Connector
+    pub fn new(
+        max_retries: usize,
+        connection_slots: Arc<ConnectionSlots>,
+        monitor: Arc<Monitor>,
+    ) -> Arc<Self> {
+        Arc::new(Self {
+            task_group: TaskGroup::new(),
+            monitor,
+            connection_slots,
+            max_retries,
+        })
+    }
+
+    /// Shuts down the connector
+    pub async fn shutdown(&self) {
+        self.task_group.cancel().await;
+    }
+
+    /// Establish a connection to the specified `endpoint`. If the connection
+    /// attempt fails, it performs a backoff and retries until the maximum allowed
+    /// number of retries is exceeded. On a successful connection, it returns a
+    /// `Conn` instance.
+    ///
+    /// This method will block until it finds an available slot.
+    pub async fn connect(&self, endpoint: &Endpoint) -> Result<Conn> {
+        self.connection_slots.wait_for_slot().await;
+        self.connection_slots.add();
+
+        let mut retry = 0;
+        let backoff = Backoff::new(500, 2000);
+        while retry < self.max_retries {
+            let conn_result = dial(endpoint).await;
+
+            if let Ok(conn) = conn_result {
+                self.monitor
+                    .notify(&ConnEvent::Connected(endpoint.clone()).into())
+                    .await;
+                return Ok(conn);
+            }
+
+            self.monitor
+                .notify(&ConnEvent::ConnectRetried(endpoint.clone()).into())
+                .await;
+
+            backoff.sleep().await;
+
+            warn!("try to reconnect {endpoint}");
+            retry += 1;
+        }
+
+        self.monitor
+            .notify(&ConnEvent::ConnectFailed(endpoint.clone()).into())
+            .await;
+
+        self.connection_slots.remove().await;
+        Err(NetError::Timeout.into())
+    }
+
+    /// Establish a connection to the given `endpoint`. For each new connection,
+    /// it invokes the provided `callback`, and pass the connection to the callback.
+    pub async fn connect_with_cback<'a, Fut>(
+        self: &Arc<Self>,
+        ex: Executor<'a>,
+        endpoint: &Endpoint,
+        callback: impl FnOnce(Conn) -> Fut + Send + 'a,
+    ) -> Result<()>
+    where
+        Fut: Future<Output = Result<()>> + Send + 'a,
+    {
+        let conn = self.connect(endpoint).await?;
+
+        let selfc = self.clone();
+        let endpoint = endpoint.clone();
+        let on_disconnect = |res| async move {
+            if let TaskResult::Completed(Err(err)) = res {
+                trace!("Outbound connection dropped: {err}");
+            }
+            selfc
+                .monitor
+                .notify(&ConnEvent::Disconnected(endpoint.clone()).into())
+                .await;
+            selfc.connection_slots.remove().await;
+        };
+
+        self.task_group
+            .spawn(ex.clone(), callback(conn), on_disconnect);
+
+        Ok(())
+    }
+}
diff --git a/p2p/src/net/listener.rs b/p2p/src/net/listener.rs
new file mode 100644
index 0000000..d1a7bfb
--- /dev/null
+++ b/p2p/src/net/listener.rs
@@ -0,0 +1,142 @@
+use std::{future::Future, sync::Arc};
+
+use log::{error, info, trace};
+
+use karyons_core::{
+    async_utils::{TaskGroup, TaskResult},
+    Executor,
+};
+
+use karyons_net::{listen, Conn, Endpoint, Listener as NetListener};
+
+use crate::{
+    monitor::{ConnEvent, Monitor},
+    Result,
+};
+
+use super::slots::ConnectionSlots;
+
+/// Responsible for creating inbound connections with other peers.
+pub struct Listener {
+    /// Managing spawned tasks.
+    task_group: TaskGroup,
+
+    /// Manages available inbound slots.
+    connection_slots: Arc<ConnectionSlots>,
+
+    /// Responsible for network and system monitoring.
+    monitor: Arc<Monitor>,
+}
+
+impl Listener {
+    /// Creates a new Listener
+    pub fn new(connection_slots: Arc<ConnectionSlots>, monitor: Arc<Monitor>) -> Arc<Self> {
+        Arc::new(Self {
+            connection_slots,
+            task_group: TaskGroup::new(),
+            monitor,
+        })
+    }
+
+    /// Starts a listener on the given `endpoint`. For each incoming connection
+    /// that is accepted, it invokes the provided `callback`, and pass the
+    /// connection to the callback.
+    ///
+    /// Returns the resloved listening endpoint.
+    pub async fn start<'a, Fut>(
+        self: &Arc<Self>,
+        ex: Executor<'a>,
+        endpoint: Endpoint,
+        // https://github.com/rust-lang/rfcs/pull/2132
+        callback: impl FnOnce(Conn) -> Fut + Clone + Send + 'a,
+    ) -> Result<Endpoint>
+    where
+        Fut: Future<Output = Result<()>> + Send + 'a,
+    {
+        let listener = match listen(&endpoint).await {
+            Ok(listener) => {
+                self.monitor
+                    .notify(&ConnEvent::Listening(endpoint.clone()).into())
+                    .await;
+                listener
+            }
+            Err(err) => {
+                error!("Failed to listen on {endpoint}: {err}");
+                self.monitor
+                    .notify(&ConnEvent::ListenFailed(endpoint).into())
+                    .await;
+                return Err(err.into());
+            }
+        };
+
+        let resolved_endpoint = listener.local_endpoint()?;
+
+        info!("Start listening on {endpoint}");
+
+        let selfc = self.clone();
+        self.task_group.spawn(
+            ex.clone(),
+            selfc.listen_loop(ex.clone(), listener, callback),
+            |res| async move {
+                if let TaskResult::Completed(Err(err)) = res {
+                    error!("Listen loop stopped: {endpoint} {err}");
+                }
+            },
+        );
+        Ok(resolved_endpoint)
+    }
+
+    /// Shuts down the listener
+    pub async fn shutdown(&self) {
+        self.task_group.cancel().await;
+    }
+
+    async fn listen_loop<'a, Fut>(
+        self: Arc<Self>,
+        ex: Executor<'a>,
+        listener: Box<dyn NetListener>,
+        callback: impl FnOnce(Conn) -> Fut + Clone + Send + 'a,
+    ) -> Result<()>
+    where
+        Fut: Future<Output = Result<()>> + Send + 'a,
+    {
+        loop {
+            // Wait for an available inbound slot.
+            self.connection_slots.wait_for_slot().await;
+            let result = listener.accept().await;
+
+            let conn = match result {
+                Ok(c) => {
+                    self.monitor
+                        .notify(&ConnEvent::Accepted(c.peer_endpoint()?).into())
+                        .await;
+                    c
+                }
+                Err(err) => {
+                    error!("Failed to accept a new connection: {err}");
+                    self.monitor.notify(&ConnEvent::AcceptFailed.into()).await;
+                    return Err(err.into());
+                }
+            };
+
+            self.connection_slots.add();
+
+            let selfc = self.clone();
+            let endpoint = conn.peer_endpoint()?;
+            let on_disconnect = |res| async move {
+                if let TaskResult::Completed(Err(err)) = res {
+                    trace!("Inbound connection dropped: {err}");
+                }
+                selfc
+                    .monitor
+                    .notify(&ConnEvent::Disconnected(endpoint).into())
+                    .await;
+                selfc.connection_slots.remove().await;
+            };
+
+            let callback = callback.clone();
+            self.task_group
+                .spawn(ex.clone(), callback(conn), on_disconnect);
+        }
+    }
+}
diff --git a/p2p/src/net/mod.rs b/p2p/src/net/mod.rs
new file mode 100644
index 0000000..9cdc748
--- /dev/null
+++ b/p2p/src/net/mod.rs
@@ -0,0 +1,27 @@
+mod connection_queue;
+mod connector;
+mod listener;
+mod slots;
+
+pub use connection_queue::ConnQueue;
+pub use connector::Connector;
+pub use listener::Listener;
+pub use slots::ConnectionSlots;
+
+use std::fmt;
+
+/// Defines the direction of a network connection.
+#[derive(Clone, Debug)]
+pub enum ConnDirection {
+    Inbound,
+    Outbound,
+}
+
+impl fmt::Display for ConnDirection {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            ConnDirection::Inbound => write!(f, "Inbound"),
+            ConnDirection::Outbound => write!(f, "Outbound"),
+        }
+    }
+}
diff --git a/p2p/src/net/slots.rs b/p2p/src/net/slots.rs
new file mode 100644
index 0000000..99f0a78
--- /dev/null
+++ b/p2p/src/net/slots.rs
@@ -0,0 +1,54 @@
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+use karyons_core::async_utils::CondWait;
+
+/// Manages available inbound and outbound slots.
+pub struct ConnectionSlots {
+    /// A condvar for notifying when a slot become available.
+    signal: CondWait,
+    /// The number of occupied slots
+    slots: AtomicUsize,
+    /// The maximum number of slots.
+    max_slots: usize,
+}
+
+impl ConnectionSlots {
+    /// Creates a new ConnectionSlots
+    pub fn new(max_slots: usize) -> Self {
+        Self {
+            signal: CondWait::new(),
+            slots: AtomicUsize::new(0),
+            max_slots,
+        }
+    }
+
+    /// Returns the number of occupied slots
+    pub fn load(&self) -> usize {
+        self.slots.load(Ordering::SeqCst)
+    }
+
+    /// Increases the occupied slots by one.
+    pub fn add(&self) {
+        self.slots.fetch_add(1, Ordering::SeqCst);
+    }
+
+    /// Decreases the occupied slots by one and notifies the waiting signal
+    /// to start accepting/connecting new connections.
+    pub async fn remove(&self) {
+        self.slots.fetch_sub(1, Ordering::SeqCst);
+        if self.slots.load(Ordering::SeqCst) < self.max_slots {
+            self.signal.signal().await;
+        }
+    }
+
+    /// Waits for a slot to become available.
+    pub async fn wait_for_slot(&self) {
+        if self.slots.load(Ordering::SeqCst) < self.max_slots {
+            return;
+        }
+
+        // Wait for a signal
+        self.signal.wait().await;
+        self.signal.reset().await;
+    }
+}
diff --git a/p2p/src/peer/mod.rs b/p2p/src/peer/mod.rs
new file mode 100644
index 0000000..ee0fdc4
--- /dev/null
+++ b/p2p/src/peer/mod.rs
@@ -0,0 +1,237 @@
+mod peer_id;
+
+pub use peer_id::PeerID;
+
+use std::sync::Arc;
+
+use log::{error, trace};
+use smol::{
+    channel::{self, Receiver, Sender},
+    lock::RwLock,
+};
+
+use karyons_core::{
+    async_utils::{select, Either, TaskGroup, TaskResult},
+    event::{ArcEventSys, EventListener, EventSys},
+    utils::{decode, encode},
+    Executor,
+};
+
+use karyons_net::Endpoint;
+
+use crate::{
+    io_codec::{CodecMsg, IOCodec},
+    message::{NetMsgCmd, ProtocolMsg, ShutdownMsg},
+    net::ConnDirection,
+    peer_pool::{ArcPeerPool, WeakPeerPool},
+    protocol::{Protocol, ProtocolEvent, ProtocolID},
+    Config, Error, Result,
+};
+
+pub type ArcPeer = Arc<Peer>;
+
+pub struct Peer {
+    /// Peer's ID
+    id: PeerID,
+
+    /// A weak pointer to `PeerPool`
+    peer_pool: WeakPeerPool,
+
+    /// Holds the IOCodec for the peer connection
+    io_codec: IOCodec,
+
+    /// Remote endpoint for the peer
+    remote_endpoint: Endpoint,
+
+    /// The direction of the connection, either `Inbound` or `Outbound`
+    conn_direction: ConnDirection,
+
+    /// A list of protocol IDs
+    protocol_ids: RwLock<Vec<ProtocolID>>,
+
+    /// `EventSys` responsible for sending events to the protocols.
+    protocol_events: ArcEventSys<ProtocolID>,
+
+    /// This channel is used to send a stop signal to the read loop.
+    stop_chan: (Sender<Result<()>>, Receiver<Result<()>>),
+
+    /// Managing spawned tasks.
+    task_group: TaskGroup,
+}
+
+impl Peer {
+    /// Creates a new peer
+    pub fn new(
+        peer_pool: WeakPeerPool,
+        id: &PeerID,
+        io_codec: IOCodec,
+        remote_endpoint: Endpoint,
+        conn_direction: ConnDirection,
+    ) -> ArcPeer {
+        Arc::new(Peer {
+            id: id.clone(),
+            peer_pool,
+            io_codec,
+            protocol_ids: RwLock::new(Vec::new()),
+            remote_endpoint,
+            conn_direction,
+            protocol_events: EventSys::new(),
+            task_group: TaskGroup::new(),
+            stop_chan: channel::bounded(1),
+        })
+    }
+
+    /// Run the peer
+    pub async fn run(self: Arc<Self>, ex: Executor<'_>) -> Result<()> {
+        self.start_protocols(ex.clone()).await;
+        self.read_loop().await
+    }
+
+    /// Send a message to the peer connection using the specified protocol.
+    pub async fn send<T: CodecMsg>(&self, protocol_id: &ProtocolID, msg: &T) -> Result<()> {
+        let payload = encode(msg)?;
+
+        let proto_msg = ProtocolMsg {
+            protocol_id: protocol_id.to_string(),
+            payload: payload.to_vec(),
+        };
+
+        self.io_codec.write(NetMsgCmd::Protocol, &proto_msg).await?;
+        Ok(())
+    }
+
+    /// Broadcast a message to all connected peers using the specified protocol.
+    pub async fn broadcast<T: CodecMsg>(&self, protocol_id: &ProtocolID, msg: &T) {
+        self.peer_pool().broadcast(protocol_id, msg).await;
+    }
+
+    /// Shuts down the peer
+    pub async fn shutdown(&self) {
+        trace!("peer {} start shutting down", self.id);
+
+        // Send shutdown event to all protocols
+        for protocol_id in self.protocol_ids.read().await.iter() {
+            self.protocol_events
+                .emit_by_topic(protocol_id, &ProtocolEvent::Shutdown)
+                .await;
+        }
+
+        // Send a stop signal to the read loop
+        //
+        // No need to handle the error here; a dropped channel and
+        // sending a stop signal have the same effect.
+        let _ = self.stop_chan.0.try_send(Ok(()));
+
+        // No need to handle the error here
+        let _ = self
+            .io_codec
+            .write(NetMsgCmd::Shutdown, &ShutdownMsg(0))
+            .await;
+
+        // Force shutting down
+        self.task_group.cancel().await;
+    }
+
+    /// Check if the connection is Inbound
+    #[inline]
+    pub fn is_inbound(&self) -> bool {
+        match self.conn_direction {
+            ConnDirection::Inbound => true,
+            ConnDirection::Outbound => false,
+        }
+    }
+
+    /// Returns the direction of the connection, which can be either `Inbound`
+    /// or `Outbound`.
+    #[inline]
+    pub fn direction(&self) -> &ConnDirection {
+        &self.conn_direction
+    }
+
+    /// Returns the remote endpoint for the peer
+    #[inline]
+    pub fn remote_endpoint(&self) -> &Endpoint {
+        &self.remote_endpoint
+    }
+
+    /// Return the peer's ID
+    #[inline]
+    pub fn id(&self) -> &PeerID {
+        &self.id
+    }
+
+    /// Returns the `Config` instance.
+    pub fn config(&self) -> Arc<Config> {
+        self.peer_pool().config.clone()
+    }
+
+    /// Registers a listener for the given Protocol `P`.
+    pub async fn register_listener<P: Protocol>(&self) -> EventListener<ProtocolID, ProtocolEvent> {
+        self.protocol_events.register(&P::id()).await
+    }
+
+    /// Start a read loop to handle incoming messages from the peer connection.
+    async fn read_loop(&self) -> Result<()> {
+        loop {
+            let fut = select(self.stop_chan.1.recv(), self.io_codec.read()).await;
+            let result = match fut {
+                Either::Left(stop_signal) => {
+                    trace!("Peer {} received a stop signal", self.id);
+                    return stop_signal?;
+                }
+                Either::Right(result) => result,
+            };
+
+            let msg = result?;
+
+            match msg.header.command {
+                NetMsgCmd::Protocol => {
+                    let msg: ProtocolMsg = decode(&msg.payload)?.0;
+
+                    if !self.protocol_ids.read().await.contains(&msg.protocol_id) {
+                        return Err(Error::UnsupportedProtocol(msg.protocol_id));
+                    }
+
+                    let proto_id = &msg.protocol_id;
+                    let msg = ProtocolEvent::Message(msg.payload);
+                    self.protocol_events.emit_by_topic(proto_id, &msg).await;
+                }
+                NetMsgCmd::Shutdown => {
+                    return Err(Error::PeerShutdown);
+                }
+                command => return Err(Error::InvalidMsg(format!("Unexpected msg {:?}", command))),
+            }
+        }
+    }
+
+    /// Start running the protocols for this peer connection.
+    async fn start_protocols(self: &Arc<Self>, ex: Executor<'_>) {
+        for (protocol_id, constructor) in self.peer_pool().protocols.read().await.iter() {
+            trace!("peer {} start protocol {protocol_id}", self.id);
+            let protocol = constructor(self.clone());
+
+            self.protocol_ids.write().await.push(protocol_id.clone());
+
+            let selfc = self.clone();
+            let exc = ex.clone();
+            let proto_idc = protocol_id.clone();
+
+            let on_failure = |result: TaskResult<Result<()>>| async move {
+                if let TaskResult::Completed(res) = result {
+                    if res.is_err() {
+                        error!("protocol {} stopped", proto_idc);
+                    }
+                    // Send a stop signal to read loop
+                    let _ = selfc.stop_chan.0.try_send(res);
+                }
+            };
+
+            self.task_group
+                .spawn(ex.clone(), protocol.start(exc), on_failure);
+        }
+    }
+
+    fn peer_pool(&self) -> ArcPeerPool {
+        self.peer_pool.upgrade().unwrap()
+    }
+}
diff --git a/p2p/src/peer/peer_id.rs b/p2p/src/peer/peer_id.rs
new file mode 100644
index 0000000..c8aec7d
--- /dev/null
+++ b/p2p/src/peer/peer_id.rs
@@ -0,0 +1,41 @@
+use bincode::{Decode, Encode};
+use rand::{rngs::OsRng, RngCore};
+use sha2::{Digest, Sha256};
+
+/// Represents a unique identifier for a peer.
+#[derive(Clone, Debug, Eq, PartialEq, Hash, Decode, Encode)]
+pub struct PeerID(pub [u8; 32]);
+
+impl std::fmt::Display for PeerID {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        let id = self.0[0..8]
+            .iter()
+            .map(|b| format!("{:x}", b))
+            .collect::<Vec<String>>()
+            .join("");
+
+        write!(f, "{}", id)
+    }
+}
+
+impl PeerID {
+    /// Creates a new PeerID.
+    pub fn new(src: &[u8]) -> Self {
+        let mut hasher = Sha256::new();
+        hasher.update(src);
+        Self(hasher.finalize().into())
+    }
+
+    /// Generates a random PeerID.
+    pub fn random() -> Self {
+        let mut id: [u8; 32] = [0; 32];
+        OsRng.fill_bytes(&mut id);
+        Self(id)
+    }
+}
+
+impl From<[u8; 32]> for PeerID {
+    fn from(b: [u8; 32]) -> Self {
+        PeerID(b)
+    }
+}
diff --git a/p2p/src/peer_pool.rs b/p2p/src/peer_pool.rs
new file mode 100644
index 0000000..eac4d3d
--- /dev/null
+++ b/p2p/src/peer_pool.rs
@@ -0,0 +1,337 @@
+use std::{
+    collections::HashMap,
+    sync::{Arc, Weak},
+    time::Duration,
+};
+
+use log::{error, info, trace, warn};
+use smol::{
+    channel::Sender,
+    lock::{Mutex, RwLock},
+};
+
+use karyons_core::{
+    async_utils::{TaskGroup, TaskResult},
+    utils::decode,
+    Executor,
+};
+
+use karyons_net::Conn;
+
+use crate::{
+    config::Config,
+    io_codec::{CodecMsg, IOCodec},
+    message::{get_msg_payload, NetMsg, NetMsgCmd, VerAckMsg, VerMsg},
+    monitor::{Monitor, PeerPoolEvent},
+    net::ConnDirection,
+    net::ConnQueue,
+    peer::{ArcPeer, Peer, PeerID},
+    protocol::{Protocol, ProtocolConstructor, ProtocolID},
+    protocols::PingProtocol,
+    utils::{version_match, Version, VersionInt},
+    Error, Result,
+};
+
+pub type ArcPeerPool = Arc<PeerPool>;
+pub type WeakPeerPool = Weak<PeerPool>;
+
+pub struct PeerPool {
+    /// Peer's ID
+    pub id: PeerID,
+
+    /// Connection queue
+    conn_queue: Arc<ConnQueue>,
+
+    /// Holds the running peers.
+    peers: Mutex<HashMap<PeerID, ArcPeer>>,
+
+    /// Hashmap contains protocol constructors.
+    pub(crate) protocols: RwLock<HashMap<ProtocolID, Box<ProtocolConstructor>>>,
+
+    /// Hashmap contains protocol IDs and their versions.
+    protocol_versions: Arc<RwLock<HashMap<ProtocolID, Version>>>,
+
+    /// Managing spawned tasks.
+    task_group: TaskGroup,
+
+    /// The Configuration for the P2P network.
+    pub config: Arc<Config>,
+
+    /// Responsible for network and system monitoring.
+    monitor: Arc<Monitor>,
+}
+
+impl PeerPool {
+    /// Creates a new PeerPool
+    pub fn new(
+        id: &PeerID,
+        conn_queue: Arc<ConnQueue>,
+        config: Arc<Config>,
+        monitor: Arc<Monitor>,
+    ) -> Arc<Self> {
+        let protocols = RwLock::new(HashMap::new());
+        let protocol_versions = Arc::new(RwLock::new(HashMap::new()));
+
+        Arc::new(Self {
+            id: id.clone(),
+            conn_queue,
+            peers: Mutex::new(HashMap::new()),
+            protocols,
+            protocol_versions,
+            task_group: TaskGroup::new(),
+            monitor,
+            config,
+        })
+    }
+
+    /// Start
+    pub async fn start(self: &Arc<Self>, ex: Executor<'_>) -> Result<()> {
+        self.setup_protocols().await?;
+        let selfc = self.clone();
+        self.task_group
+            .spawn(ex.clone(), selfc.listen_loop(ex.clone()), |_| async {});
+        Ok(())
+    }
+
+    /// Listens to a new connection from the connection queue
+    pub async fn listen_loop(self: Arc<Self>, ex: Executor<'_>) {
+        loop {
+            let new_conn = self.conn_queue.next().await;
+            let disconnect_signal = new_conn.disconnect_signal;
+
+            let result = self
+                .new_peer(
+                    new_conn.conn,
+                    &new_conn.direction,
+                    disconnect_signal.clone(),
+                    ex.clone(),
+                )
+                .await;
+
+            if result.is_err() {
+                let _ = disconnect_signal.send(()).await;
+            }
+        }
+    }
+
+    /// Shuts down
+    pub async fn shutdown(&self) {
+        for (_, peer) in self.peers.lock().await.iter() {
+            peer.shutdown().await;
+        }
+
+        self.task_group.cancel().await;
+    }
+
+    /// Attach a custom protocol to the network
+    pub async fn attach_protocol<P: Protocol>(&self, c: Box<ProtocolConstructor>) -> Result<()> {
+        let protocol_versions = &mut self.protocol_versions.write().await;
+        let protocols = &mut self.protocols.write().await;
+
+        protocol_versions.insert(P::id(), P::version()?);
+        protocols.insert(P::id(), Box::new(c) as Box<ProtocolConstructor>);
+        Ok(())
+    }
+
+    /// Returns the number of currently connected peers.
+    pub async fn peers_len(&self) -> usize {
+        self.peers.lock().await.len()
+    }
+
+    /// Broadcast a message to all connected peers using the specified protocol.
+    pub async fn broadcast<T: CodecMsg>(&self, proto_id: &ProtocolID, msg: &T) {
+        for (pid, peer) in self.peers.lock().await.iter() {
+            if let Err(err) = peer.send(proto_id, msg).await {
+                error!("failed to send msg to {pid}: {err}");
+                continue;
+            }
+        }
+    }
+
+    /// Add a new peer to the peer list.
+    pub async fn new_peer(
+        self: &Arc<Self>,
+        conn: Conn,
+        conn_direction: &ConnDirection,
+        disconnect_signal: Sender<()>,
+        ex: Executor<'_>,
+    ) -> Result<PeerID> {
+        let endpoint = conn.peer_endpoint()?;
+        let io_codec = IOCodec::new(conn);
+
+        // Do a handshake with a connection before creating a new peer.
+        let pid = self.do_handshake(&io_codec, conn_direction).await?;
+
+        // TODO: Consider restricting the subnet for inbound connections
+        if self.contains_peer(&pid).await {
+            return Err(Error::PeerAlreadyConnected);
+        }
+
+        // Create a new peer
+        let peer = Peer::new(
+            Arc::downgrade(self),
+            &pid,
+            io_codec,
+            endpoint.clone(),
+            conn_direction.clone(),
+        );
+
+        // Insert the new peer
+        self.peers.lock().await.insert(pid.clone(), peer.clone());
+
+        let selfc = self.clone();
+        let pid_c = pid.clone();
+        let on_disconnect = |result| async move {
+            if let TaskResult::Completed(_) = result {
+                if let Err(err) = selfc.remove_peer(&pid_c).await {
+                    error!("Failed to remove peer {pid_c}: {err}");
+                }
+                let _ = disconnect_signal.send(()).await;
+            }
+        };
+
+        self.task_group
+            .spawn(ex.clone(), peer.run(ex.clone()), on_disconnect);
+
+        info!("Add new peer {pid}, direction: {conn_direction}, endpoint: {endpoint}");
+
+        self.monitor
+            .notify(&PeerPoolEvent::NewPeer(pid.clone()).into())
+            .await;
+        Ok(pid)
+    }
+
+    /// Checks if the peer list contains a peer with the given peer id
+    pub async fn contains_peer(&self, pid: &PeerID) -> bool {
+        self.peers.lock().await.contains_key(pid)
+    }
+
+    /// Shuts down the peer and remove it from the peer list.
+    async fn remove_peer(&self, pid: &PeerID) -> Result<()> {
+        let mut peers = self.peers.lock().await;
+        let result = peers.remove(pid);
+
+        drop(peers);
+
+        let peer = match result {
+            Some(p) => p,
+            None => return Ok(()),
+        };
+
+        peer.shutdown().await;
+
+        self.monitor
+            .notify(&PeerPoolEvent::RemovePeer(pid.clone()).into())
+            .await;
+
+        let endpoint = peer.remote_endpoint();
+        let direction = peer.direction();
+
+        warn!("Peer {pid} removed, direction: {direction}, endpoint: {endpoint}",);
+        Ok(())
+    }
+
+    /// Attach the core protocols.
+    async fn setup_protocols(&self) -> Result<()> {
+        self.attach_protocol::<PingProtocol>(Box::new(PingProtocol::new))
+            .await
+    }
+
+    /// Initiate a handshake with a connection.
+    async fn do_handshake(
+        &self,
+        io_codec: &IOCodec,
+        conn_direction: &ConnDirection,
+    ) -> Result<PeerID> {
+        match conn_direction {
+            ConnDirection::Inbound => {
+                let pid = self.wait_vermsg(io_codec).await?;
+                self.send_verack(io_codec).await?;
+                Ok(pid)
+            }
+            ConnDirection::Outbound => {
+                self.send_vermsg(io_codec).await?;
+                self.wait_verack(io_codec).await
+            }
+        }
+    }
+
+    /// Send a Version message
+    async fn send_vermsg(&self, io_codec: &IOCodec) -> Result<()> {
+        let pids = self.protocol_versions.read().await;
+        let protocols = pids.iter().map(|p| (p.0.clone(), p.1.v.clone())).collect();
+        drop(pids);
+
+        let vermsg = VerMsg {
+            peer_id: self.id.clone(),
+            protocols,
+            version: self.config.version.v.clone(),
+        };
+
+        trace!("Send VerMsg");
+        io_codec.write(NetMsgCmd::Version, &vermsg).await?;
+        Ok(())
+    }
+
+    /// Wait for a Version message
+    ///
+    /// Returns the peer's ID upon successfully receiving the Version message.
+    async fn wait_vermsg(&self, io_codec: &IOCodec) -> Result<PeerID> {
+        let timeout = Duration::from_secs(self.config.handshake_timeout);
+        let msg: NetMsg = io_codec.read_timeout(timeout).await?;
+
+        let payload = get_msg_payload!(Version, msg);
+        let (vermsg, _) = decode::<VerMsg>(&payload)?;
+
+        if !version_match(&self.config.version.req, &vermsg.version) {
+            return Err(Error::IncompatibleVersion("system: {}".into()));
+        }
+
+        self.protocols_match(&vermsg.protocols).await?;
+
+        trace!("Received VerMsg from: {}", vermsg.peer_id);
+        Ok(vermsg.peer_id)
+    }
+
+    /// Send a Verack message
+    async fn send_verack(&self, io_codec: &IOCodec) -> Result<()> {
+        let verack = VerAckMsg(self.id.clone());
+
+        trace!("Send VerAckMsg");
+        io_codec.write(NetMsgCmd::Verack, &verack).await?;
+        Ok(())
+    }
+
+    /// Wait for a Verack message
+    ///
+    /// Returns the peer's ID upon successfully receiving the Verack message.
+    async fn wait_verack(&self, io_codec: &IOCodec) -> Result<PeerID> {
+        let timeout = Duration::from_secs(self.config.handshake_timeout);
+        let msg: NetMsg = io_codec.read_timeout(timeout).await?;
+
+        let payload = get_msg_payload!(Verack, msg);
+        let (verack, _) = decode::<VerAckMsg>(&payload)?;
+
+        trace!("Received VerAckMsg from: {}", verack.0);
+        Ok(verack.0)
+    }
+
+    /// Check if the new connection has compatible protocols.
+    async fn protocols_match(&self, protocols: &HashMap<ProtocolID, VersionInt>) -> Result<()> {
+        for (n, pv) in protocols.iter() {
+            let pids = self.protocol_versions.read().await;
+
+            match pids.get(n) {
+                Some(v) => {
+                    if !version_match(&v.req, pv) {
+                        return Err(Error::IncompatibleVersion(format!("{n} protocol: {pv}")));
+                    }
+                }
+                None => {
+                    return Err(Error::UnsupportedProtocol(n.to_string()));
+                }
+            }
+        }
+        Ok(())
+    }
+}
diff --git a/p2p/src/protocol.rs b/p2p/src/protocol.rs
new file mode 100644
index 0000000..515efc6
--- /dev/null
+++ b/p2p/src/protocol.rs
@@ -0,0 +1,113 @@
+use std::sync::Arc;
+
+use async_trait::async_trait;
+
+use karyons_core::{event::EventValue, Executor};
+
+use crate::{peer::ArcPeer, utils::Version, Result};
+
+pub type ArcProtocol = Arc<dyn Protocol>;
+
+pub type ProtocolConstructor = dyn Fn(ArcPeer) -> Arc<dyn Protocol> + Send + Sync;
+
+pub type ProtocolID = String;
+
+/// Protocol event
+#[derive(Debug, Clone)]
+pub enum ProtocolEvent {
+    /// Message event, contains a vector of bytes.
+    Message(Vec<u8>),
+    /// Shutdown event signals the protocol to gracefully shut down.
+    Shutdown,
+}
+
+impl EventValue for ProtocolEvent {
+    fn id() -> &'static str {
+        "ProtocolEvent"
+    }
+}
+
+/// The Protocol trait defines the interface for core protocols
+/// and custom protocols.
+///
+/// # Example
+/// ```
+/// use std::sync::Arc;
+///
+/// use async_trait::async_trait;
+/// use smol::Executor;
+///
+/// use karyons_p2p::{
+///     protocol::{ArcProtocol, Protocol, ProtocolID, ProtocolEvent},
+///     Backend, PeerID, Config, Version, P2pError, ArcPeer};
+///
+/// pub struct NewProtocol {
+///     peer: ArcPeer,
+/// }
+///
+/// impl NewProtocol {
+///     fn new(peer: ArcPeer) -> ArcProtocol {
+///         Arc::new(Self {
+///             peer,
+///         })
+///     }
+/// }
+///
+/// #[async_trait]
+/// impl Protocol for NewProtocol {
+///     async fn start(self: Arc<Self>, ex: Arc<Executor<'_>>) -> Result<(), P2pError> {
+///         let listener = self.peer.register_listener::<Self>().await;
+///         loop {
+///             let event = listener.recv().await.unwrap();
+///
+///             match event {
+///                 ProtocolEvent::Message(msg) => {
+///                     println!("{:?}", msg);
+///                 }
+///                 ProtocolEvent::Shutdown => {
+///                     break;
+///                 }
+///             }
+///         }
+///
+///         listener.cancel().await;
+///         Ok(())
+///     }
+///
+///     fn version() -> Result<Version, P2pError> {
+///         "0.2.0, >0.1.0".parse()
+///     }
+///
+///     fn id() -> ProtocolID {
+///         "NEWPROTOCOLID".into()
+///     }
+/// }
+///
+///  async {
+///     let peer_id = PeerID::random();
+///     let config = Config::default();
+///
+///     // Create a new Backend
+///     let backend = Backend::new(peer_id, config);
+///
+///     // Attach the NewProtocol
+///     let c = move |peer| NewProtocol::new(peer);
+///     backend.attach_protocol::<NewProtocol>(c).await.unwrap();
+///  };
+///
+/// ```  
+#[async_trait]
+pub trait Protocol: Send + Sync {
+    /// Start the protocol
+    async fn start(self: Arc<Self>, ex: Executor<'_>) -> Result<()>;
+
+    /// Returns the version of the protocol.
+    fn version() -> Result<Version>
+    where
+        Self: Sized;
+
+    /// Returns the unique ProtocolID associated with the protocol.
+    fn id() -> ProtocolID
+    where
+        Self: Sized;
+}
diff --git a/p2p/src/protocols/mod.rs b/p2p/src/protocols/mod.rs
new file mode 100644
index 0000000..4a8f6b9
--- /dev/null
+++ b/p2p/src/protocols/mod.rs
@@ -0,0 +1,3 @@
+mod ping;
+
+pub use ping::PingProtocol;
diff --git a/p2p/src/protocols/ping.rs b/p2p/src/protocols/ping.rs
new file mode 100644
index 0000000..b337494
--- /dev/null
+++ b/p2p/src/protocols/ping.rs
@@ -0,0 +1,173 @@
+use std::{sync::Arc, time::Duration};
+
+use async_trait::async_trait;
+use bincode::{Decode, Encode};
+use log::trace;
+use rand::{rngs::OsRng, RngCore};
+use smol::{
+    channel,
+    channel::{Receiver, Sender},
+    stream::StreamExt,
+    Timer,
+};
+
+use karyons_core::{
+    async_utils::{select, timeout, Either, TaskGroup, TaskResult},
+    event::EventListener,
+    utils::decode,
+    Executor,
+};
+
+use karyons_net::NetError;
+
+use crate::{
+    peer::ArcPeer,
+    protocol::{ArcProtocol, Protocol, ProtocolEvent, ProtocolID},
+    utils::Version,
+    Result,
+};
+
+const MAX_FAILUERS: u32 = 3;
+
+#[derive(Clone, Debug, Encode, Decode)]
+enum PingProtocolMsg {
+    Ping([u8; 32]),
+    Pong([u8; 32]),
+}
+
+pub struct PingProtocol {
+    peer: ArcPeer,
+    ping_interval: u64,
+    ping_timeout: u64,
+    task_group: TaskGroup,
+}
+
+impl PingProtocol {
+    #[allow(clippy::new_ret_no_self)]
+    pub fn new(peer: ArcPeer) -> ArcProtocol {
+        let ping_interval = peer.config().ping_interval;
+        let ping_timeout = peer.config().ping_timeout;
+        Arc::new(Self {
+            peer,
+            ping_interval,
+            ping_timeout,
+            task_group: TaskGroup::new(),
+        })
+    }
+
+    async fn recv_loop(
+        &self,
+        listener: &EventListener<ProtocolID, ProtocolEvent>,
+        pong_chan: Sender<[u8; 32]>,
+    ) -> Result<()> {
+        loop {
+            let event = listener.recv().await?;
+            let msg_payload = match event.clone() {
+                ProtocolEvent::Message(m) => m,
+                ProtocolEvent::Shutdown => {
+                    break;
+                }
+            };
+
+            let (msg, _) = decode::<PingProtocolMsg>(&msg_payload)?;
+
+            match msg {
+                PingProtocolMsg::Ping(nonce) => {
+                    trace!("Received Ping message {:?}", nonce);
+                    self.peer
+                        .send(&Self::id(), &PingProtocolMsg::Pong(nonce))
+                        .await?;
+                    trace!("Send back Pong message {:?}", nonce);
+                }
+                PingProtocolMsg::Pong(nonce) => {
+                    pong_chan.send(nonce).await?;
+                }
+            }
+        }
+        Ok(())
+    }
+
+    async fn ping_loop(self: Arc<Self>, chan: Receiver<[u8; 32]>) -> Result<()> {
+        let mut timer = Timer::interval(Duration::from_secs(self.ping_interval));
+        let rng = &mut OsRng;
+        let mut retry = 0;
+
+        while retry < MAX_FAILUERS {
+            timer.next().await;
+
+            let mut ping_nonce: [u8; 32] = [0; 32];
+            rng.fill_bytes(&mut ping_nonce);
+
+            trace!("Send Ping message {:?}", ping_nonce);
+            self.peer
+                .send(&Self::id(), &PingProtocolMsg::Ping(ping_nonce))
+                .await?;
+
+            let d = Duration::from_secs(self.ping_timeout);
+
+            // Wait for Pong message
+            let pong_msg = match timeout(d, chan.recv()).await {
+                Ok(m) => m?,
+                Err(_) => {
+                    retry += 1;
+                    continue;
+                }
+            };
+
+            trace!("Received Pong message {:?}", pong_msg);
+
+            if pong_msg != ping_nonce {
+                retry += 1;
+                continue;
+            }
+        }
+
+        Err(NetError::Timeout.into())
+    }
+}
+
+#[async_trait]
+impl Protocol for PingProtocol {
+    async fn start(self: Arc<Self>, ex: Executor<'_>) -> Result<()> {
+        trace!("Start Ping protocol");
+        let (pong_chan, pong_chan_recv) = channel::bounded(1);
+        let (stop_signal_s, stop_signal) = channel::bounded::<Result<()>>(1);
+
+        let selfc = self.clone();
+        self.task_group.spawn(
+            ex.clone(),
+            selfc.clone().ping_loop(pong_chan_recv.clone()),
+            |res| async move {
+                if let TaskResult::Completed(result) = res {
+                    let _ = stop_signal_s.send(result).await;
+                }
+            },
+        );
+
+        let listener = self.peer.register_listener::<Self>().await;
+
+        let result = select(self.recv_loop(&listener, pong_chan), stop_signal.recv()).await;
+        listener.cancel().await;
+        self.task_group.cancel().await;
+
+        match result {
+            Either::Left(res) => {
+                trace!("Receive loop stopped {:?}", res);
+                res
+            }
+            Either::Right(res) => {
+                let res = res?;
+                trace!("Ping loop stopped {:?}", res);
+                res
+            }
+        }
+    }
+
+    fn version() -> Result<Version> {
+        "0.1.0".parse()
+    }
+
+    fn id() -> ProtocolID {
+        "PING".into()
+    }
+}
diff --git a/p2p/src/routing_table/bucket.rs b/p2p/src/routing_table/bucket.rs
new file mode 100644
index 0000000..13edd24
--- /dev/null
+++ b/p2p/src/routing_table/bucket.rs
@@ -0,0 +1,123 @@
+use super::{Entry, Key};
+
+use rand::{rngs::OsRng, seq::SliceRandom};
+
+/// BITFLAGS represent the status of an Entry within a bucket.
+pub type EntryStatusFlag = u16;
+
+/// The entry is connected.
+pub const CONNECTED_ENTRY: EntryStatusFlag = 0b00001;
+
+/// The entry is disconnected. This will increase the failure counter.
+pub const DISCONNECTED_ENTRY: EntryStatusFlag = 0b00010;
+
+/// The entry is ready to reconnect, meaning it has either been added and
+/// has no connection attempts, or it has been refreshed.
+pub const PENDING_ENTRY: EntryStatusFlag = 0b00100;
+
+/// The entry is unreachable. This will increase the failure counter.
+pub const UNREACHABLE_ENTRY: EntryStatusFlag = 0b01000;
+
+/// The entry is unstable. This will increase the failure counter.
+pub const UNSTABLE_ENTRY: EntryStatusFlag = 0b10000;
+
+#[allow(dead_code)]
+pub const ALL_ENTRY: EntryStatusFlag = 0b11111;
+
+/// A BucketEntry represents a peer in the routing table.
+#[derive(Clone, Debug)]
+pub struct BucketEntry {
+    pub status: EntryStatusFlag,
+    pub entry: Entry,
+    pub failures: u32,
+    pub last_seen: i64,
+}
+
+impl BucketEntry {
+    pub fn is_connected(&self) -> bool {
+        self.status ^ CONNECTED_ENTRY == 0
+    }
+
+    pub fn is_unreachable(&self) -> bool {
+        self.status ^ UNREACHABLE_ENTRY == 0
+    }
+
+    pub fn is_unstable(&self) -> bool {
+        self.status ^ UNSTABLE_ENTRY == 0
+    }
+}
+
+/// The number of entries that can be stored within a single bucket.
+pub const BUCKET_SIZE: usize = 20;
+
+/// A Bucket represents a group of entries in the routing table.
+#[derive(Debug, Clone)]
+pub struct Bucket {
+    entries: Vec<BucketEntry>,
+}
+
+impl Bucket {
+    /// Creates a new empty Bucket
+    pub fn new() -> Self {
+        Self {
+            entries: Vec::with_capacity(BUCKET_SIZE),
+        }
+    }
+
+    /// Add an entry to the bucket.
+    pub fn add(&mut self, entry: &Entry) {
+        self.entries.push(BucketEntry {
+            status: PENDING_ENTRY,
+            entry: entry.clone(),
+            failures: 0,
+            last_seen: chrono::Utc::now().timestamp(),
+        })
+    }
+
+    /// Get the number of entries in the bucket.
+    pub fn len(&self) -> usize {
+        self.entries.len()
+    }
+
+    /// Returns an iterator over the entries in the bucket.
+    pub fn iter(&self) -> impl Iterator<Item = &BucketEntry> {
+        self.entries.iter()
+    }
+
+    /// Remove an entry.
+    pub fn remove(&mut self, key: &Key) {
+        let position = self.entries.iter().position(|e| &e.entry.key == key);
+        if let Some(i) = position {
+            self.entries.remove(i);
+        }
+    }
+
+    /// Returns an iterator of entries in random order.
+    pub fn random_iter(&self, amount: usize) -> impl Iterator<Item = &BucketEntry> {
+        self.entries.choose_multiple(&mut OsRng, amount)
+    }
+
+    /// Updates the status of an entry in the bucket identified by the given key.
+    ///
+    /// If the key is not found in the bucket, no action is taken.
+    ///
+    /// This will also update the last_seen field and increase the failures
+    /// counter for the bucket entry according to the new status.
+    pub fn update_entry(&mut self, key: &Key, entry_flag: EntryStatusFlag) {
+        if let Some(e) = self.entries.iter_mut().find(|e| &e.entry.key == key) {
+            e.status = entry_flag;
+            if e.is_unreachable() || e.is_unstable() {
+                e.failures += 1;
+            }
+
+            if !e.is_unreachable() {
+                e.last_seen = chrono::Utc::now().timestamp();
+            }
+        }
+    }
+
+    /// Check if the bucket contains the given key.
+    pub fn contains_key(&self, key: &Key) -> bool {
+        self.entries.iter().any(|e| &e.entry.key == key)
+    }
+}
diff --git a/p2p/src/routing_table/entry.rs b/p2p/src/routing_table/entry.rs
new file mode 100644
index 0000000..b3f219f
--- /dev/null
+++ b/p2p/src/routing_table/entry.rs
@@ -0,0 +1,41 @@
+use bincode::{Decode, Encode};
+
+use karyons_net::{Addr, Port};
+
+/// Specifies the size of the key, in bytes.
+pub const KEY_SIZE: usize = 32;
+
+/// An Entry represents a peer in the routing table.
+#[derive(Encode, Decode, Clone, Debug)]
+pub struct Entry {
+    /// The unique key identifying the peer.
+    pub key: Key,
+    /// The IP address of the peer.
+    pub addr: Addr,
+    /// TCP port
+    pub port: Port,
+    /// UDP/TCP port
+    pub discovery_port: Port,
+}
+
+impl PartialEq for Entry {
+    fn eq(&self, other: &Self) -> bool {
+        // XXX this should also compare both addresses (the self.addr == other.addr)
+        self.key == other.key
+    }
+}
+
+/// The unique key identifying the peer.
+pub type Key = [u8; KEY_SIZE];
+
+/// Calculates the XOR distance between two provided keys.
+///
+/// The XOR distance is a metric used in Kademlia to measure the closeness
+/// of keys.
+pub fn xor_distance(key: &Key, other: &Key) -> Key {
+    let mut res = [0; 32];
+    for (i, (k, o)) in key.iter().zip(other.iter()).enumerate() {
+        res[i] = k ^ o;
+    }
+    res
+}
diff --git a/p2p/src/routing_table/mod.rs b/p2p/src/routing_table/mod.rs
new file mode 100644
index 0000000..abf9a08
--- /dev/null
+++ b/p2p/src/routing_table/mod.rs
@@ -0,0 +1,461 @@
+mod bucket;
+mod entry;
+pub use bucket::{
+    Bucket, BucketEntry, EntryStatusFlag, CONNECTED_ENTRY, DISCONNECTED_ENTRY, PENDING_ENTRY,
+    UNREACHABLE_ENTRY, UNSTABLE_ENTRY,
+};
+pub use entry::{xor_distance, Entry, Key};
+
+use rand::{rngs::OsRng, seq::SliceRandom};
+
+use crate::utils::subnet_match;
+
+use bucket::BUCKET_SIZE;
+use entry::KEY_SIZE;
+
+/// The total number of buckets in the routing table.
+const TABLE_SIZE: usize = 32;
+
+/// The distance limit for the closest buckets.
+const DISTANCE_LIMIT: usize = 32;
+
+/// The maximum number of matched subnets allowed within a single bucket.
+const MAX_MATCHED_SUBNET_IN_BUCKET: usize = 1;
+
+/// The maximum number of matched subnets across the entire routing table.
+const MAX_MATCHED_SUBNET_IN_TABLE: usize = 6;
+
+/// Represents the possible result when adding a new entry.
+#[derive(Debug)]
+pub enum AddEntryResult {
+    /// The entry is added.
+    Added,
+    /// The entry is already exists.
+    Exists,
+    /// The entry is ignored.
+    Ignored,
+    /// The entry is restricted and not allowed.
+    Restricted,
+}
+
+/// This is a modified version of the Kademlia Distributed Hash Table (DHT).
+/// https://en.wikipedia.org/wiki/Kademlia
+#[derive(Debug)]
+pub struct RoutingTable {
+    key: Key,
+    buckets: Vec<Bucket>,
+}
+
+impl RoutingTable {
+    /// Creates a new RoutingTable
+    pub fn new(key: Key) -> Self {
+        let buckets: Vec<Bucket> = (0..TABLE_SIZE).map(|_| Bucket::new()).collect();
+        Self { key, buckets }
+    }
+
+    /// Adds a new entry to the table and returns a result indicating success,
+    /// failure, or restrictions.
+    pub fn add_entry(&mut self, entry: Entry) -> AddEntryResult {
+        // Determine the index of the bucket where the entry should be placed.
+        let bucket_idx = match self.bucket_index(&entry.key) {
+            Some(i) => i,
+            None => return AddEntryResult::Ignored,
+        };
+
+        let bucket = &self.buckets[bucket_idx];
+
+        // Check if the entry already exists in the bucket.
+        if bucket.contains_key(&entry.key) {
+            return AddEntryResult::Exists;
+        }
+
+        // Check if the entry is restricted.
+        if self.subnet_restricted(bucket_idx, &entry) {
+            return AddEntryResult::Restricted;
+        }
+
+        let bucket = &mut self.buckets[bucket_idx];
+
+        // If the bucket has free space, add the entry and return success.
+        if bucket.len() < BUCKET_SIZE {
+            bucket.add(&entry);
+            return AddEntryResult::Added;
+        }
+
+        // If the bucket is full, the entry is ignored.
+        AddEntryResult::Ignored
+    }
+
+    /// Check if the table contains the given key.
+    pub fn contains_key(&self, key: &Key) -> bool {
+        // Determine the bucket index for the given key.
+        let bucket_idx = match self.bucket_index(key) {
+            Some(bi) => bi,
+            None => return false,
+        };
+
+        let bucket = &self.buckets[bucket_idx];
+        bucket.contains_key(key)
+    }
+
+    /// Updates the status of an entry in the routing table identified
+    /// by the given key.
+    ///
+    /// If the key is not found, no action is taken.
+    pub fn update_entry(&mut self, key: &Key, entry_flag: EntryStatusFlag) {
+        // Determine the bucket index for the given key.
+        let bucket_idx = match self.bucket_index(key) {
+            Some(bi) => bi,
+            None => return,
+        };
+
+        let bucket = &mut self.buckets[bucket_idx];
+        bucket.update_entry(key, entry_flag);
+    }
+
+    /// Returns a list of bucket indexes that are closest to the given target key.
+    pub fn bucket_indexes(&self, target_key: &Key) -> Vec<usize> {
+        let mut indexes = vec![];
+
+        // Determine the primary bucket index for the target key.
+        let bucket_idx = self.bucket_index(target_key).unwrap_or(0);
+
+        indexes.push(bucket_idx);
+
+        // Add additional bucket indexes within a certain distance limit.
+        for i in 1..DISTANCE_LIMIT {
+            if bucket_idx >= i && bucket_idx - i >= 1 {
+                indexes.push(bucket_idx - i);
+            }
+
+            if bucket_idx + i < (TABLE_SIZE - 1) {
+                indexes.push(bucket_idx + i);
+            }
+        }
+
+        indexes
+    }
+
+    /// Returns a list of the closest entries to the given target key, limited by max_entries.
+    pub fn closest_entries(&self, target_key: &Key, max_entries: usize) -> Vec<Entry> {
+        let mut entries: Vec<Entry> = vec![];
+
+        // Collect entries
+        'outer: for idx in self.bucket_indexes(target_key) {
+            let bucket = &self.buckets[idx];
+            for bucket_entry in bucket.iter() {
+                if bucket_entry.is_unreachable() || bucket_entry.is_unstable() {
+                    continue;
+                }
+
+                entries.push(bucket_entry.entry.clone());
+                if entries.len() == max_entries {
+                    break 'outer;
+                }
+            }
+        }
+
+        // Sort the entries by their distance to the target key.
+        entries.sort_by(|a, b| {
+            xor_distance(target_key, &a.key).cmp(&xor_distance(target_key, &b.key))
+        });
+
+        entries
+    }
+
+    /// Removes an entry with the given key from the routing table, if it exists.
+    pub fn remove_entry(&mut self, key: &Key) {
+        // Determine the bucket index for the given key.
+        let bucket_idx = match self.bucket_index(key) {
+            Some(bi) => bi,
+            None => return,
+        };
+
+        let bucket = &mut self.buckets[bucket_idx];
+        bucket.remove(key);
+    }
+
+    /// Returns an iterator of entries.
+    pub fn iter(&self) -> impl Iterator<Item = &Bucket> {
+        self.buckets.iter()
+    }
+
+    /// Returns a random entry from the routing table.
+    pub fn random_entry(&self, entry_flag: EntryStatusFlag) -> Option<&Entry> {
+        for bucket in self.buckets.choose_multiple(&mut OsRng, self.buckets.len()) {
+            for entry in bucket.random_iter(bucket.len()) {
+                if entry.status & entry_flag == 0 {
+                    continue;
+                }
+                return Some(&entry.entry);
+            }
+        }
+
+        None
+    }
+
+    // Returns the bucket index for a given key in the table.
+    fn bucket_index(&self, key: &Key) -> Option<usize> {
+        // Calculate the XOR distance between the self key and the provided key.
+        let distance = xor_distance(&self.key, key);
+
+        for (i, b) in distance.iter().enumerate() {
+            if *b != 0 {
+                let lz = i * 8 + b.leading_zeros() as usize;
+                let bits = KEY_SIZE * 8 - 1;
+                let idx = (bits - lz) / 8;
+                return Some(idx);
+            }
+        }
+        None
+    }
+
+    /// This function iterate through the routing table and counts how many
+    /// entries in the same subnet as the given Entry are already present.
+    ///
+    /// If the number of matching entries in the same bucket exceeds a
+    /// threshold (MAX_MATCHED_SUBNET_IN_BUCKET), or if the total count of
+    /// matching entries in the entire table exceeds a threshold
+    /// (MAX_MATCHED_SUBNET_IN_TABLE), the addition of the Entry
+    /// is considered restricted and returns true.
+    fn subnet_restricted(&self, idx: usize, entry: &Entry) -> bool {
+        let mut bucket_count = 0;
+        let mut table_count = 0;
+
+        // Iterate through the routing table's buckets and entries to check
+        // for subnet matches.
+        for (i, bucket) in self.buckets.iter().enumerate() {
+            for e in bucket.iter() {
+                // If there is a subnet match, update the counts.
+                let matched = subnet_match(&e.entry.addr, &entry.addr);
+                if matched {
+                    if i == idx {
+                        bucket_count += 1;
+                    }
+                    table_count += 1;
+                }
+
+                // If the number of matched entries in the same bucket exceeds
+                // the limit, return true
+                if bucket_count >= MAX_MATCHED_SUBNET_IN_BUCKET {
+                    return true;
+                }
+            }
+
+            // If the total matched entries in the table exceed the limit,
+            // return true.
+            if table_count >= MAX_MATCHED_SUBNET_IN_TABLE {
+                return true;
+            }
+        }
+
+        // If no subnet restrictions are encountered, return false.
+        false
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::bucket::ALL_ENTRY;
+    use super::*;
+
+    use karyons_net::Addr;
+
+    struct Setup {
+        local_key: Key,
+        keys: Vec<Key>,
+    }
+
+    fn new_entry(key: &Key, addr: &Addr, port: u16, discovery_port: u16) -> Entry {
+        Entry {
+            key: key.clone(),
+            addr: addr.clone(),
+            port,
+            discovery_port,
+        }
+    }
+
+    impl Setup {
+        fn new() -> Self {
+            let keys = vec![
+                [
+                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                    0, 0, 0, 0, 0, 1,
+                ],
+                [
+                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                    1, 1, 0, 1, 1, 2,
+                ],
+                [
+                    0, 0, 0, 0, 0, 20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                    0, 0, 0, 0, 0, 3,
+                ],
+                [
+                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 30, 1, 18, 0, 0, 0,
+                    0, 0, 0, 0, 0, 4,
+                ],
+                [
+                    223, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                    0, 0, 0, 0, 0, 5,
+                ],
+                [
+                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 50, 1, 18, 0, 0, 0,
+                    0, 0, 0, 0, 0, 6,
+                ],
+                [
+                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 50, 1, 18, 0, 0,
+                    0, 0, 0, 0, 0, 0, 7,
+                ],
+                [
+                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 10, 50, 1, 18, 0, 0,
+                    0, 0, 0, 0, 0, 0, 8,
+                ],
+                [
+                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 10, 10, 50, 1, 18, 0, 0,
+                    0, 0, 0, 0, 0, 0, 9,
+                ],
+            ];
+
+            Self {
+                local_key: [
+                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                    0, 0, 0, 0, 0, 0,
+                ],
+                keys,
+            }
+        }
+
+        fn entries(&self) -> Vec<Entry> {
+            let mut entries = vec![];
+            for (i, key) in self.keys.iter().enumerate() {
+                entries.push(new_entry(
+                    key,
+                    &Addr::Ip(format!("127.0.{i}.1").parse().unwrap()),
+                    3000,
+                    3010,
+                ));
+            }
+            entries
+        }
+
+        fn table(&self) -> RoutingTable {
+            let mut table = RoutingTable::new(self.local_key.clone());
+
+            for entry in self.entries() {
+                let res = table.add_entry(entry);
+                assert!(matches!(res, AddEntryResult::Added));
+            }
+
+            table
+        }
+    }
+
+    #[test]
+    fn test_bucket_index() {
+        let setup = Setup::new();
+        let table = setup.table();
+
+        assert_eq!(table.bucket_index(&setup.local_key), None);
+        assert_eq!(table.bucket_index(&setup.keys[0]), Some(0));
+        assert_eq!(table.bucket_index(&setup.keys[1]), Some(5));
+        assert_eq!(table.bucket_index(&setup.keys[2]), Some(26));
+        assert_eq!(table.bucket_index(&setup.keys[3]), Some(11));
+        assert_eq!(table.bucket_index(&setup.keys[4]), Some(31));
+        assert_eq!(table.bucket_index(&setup.keys[5]), Some(11));
+        assert_eq!(table.bucket_index(&setup.keys[6]), Some(12));
+        assert_eq!(table.bucket_index(&setup.keys[7]), Some(13));
+        assert_eq!(table.bucket_index(&setup.keys[8]), Some(14));
+    }
+
+    #[test]
+    fn test_closest_entries() {
+        let setup = Setup::new();
+        let table = setup.table();
+        let entries = setup.entries();
+
+        assert_eq!(
+            table.closest_entries(&setup.keys[5], 8),
+            vec![
+                entries[5].clone(),
+                entries[3].clone(),
+                entries[1].clone(),
+                entries[6].clone(),
+                entries[7].clone(),
+                entries[8].clone(),
+                entries[2].clone(),
+            ]
+        );
+
+        assert_eq!(
+            table.closest_entries(&setup.keys[4], 2),
+            vec![entries[4].clone(), entries[2].clone()]
+        );
+    }
+
+    #[test]
+    fn test_random_entry() {
+        let setup = Setup::new();
+        let mut table = setup.table();
+        let entries = setup.entries();
+
+        let entry = table.random_entry(ALL_ENTRY);
+        assert!(matches!(entry, Some(&_)));
+
+        let entry = table.random_entry(CONNECTED_ENTRY);
+        assert!(matches!(entry, None));
+
+        for entry in entries {
+            table.remove_entry(&entry.key);
+        }
+
+        let entry = table.random_entry(ALL_ENTRY);
+        assert!(matches!(entry, None));
+    }
+
+    #[test]
+    fn test_add_entries() {
+        let setup = Setup::new();
+        let mut table = setup.table();
+
+        let key = [
+            0, 0, 0, 0, 0, 0, 0, 1, 3, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 5,
+        ];
+
+        let key2 = [
+            0, 0, 0, 0, 0, 0, 0, 1, 2, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+            0, 0, 5,
+        ];
+
+        let entry1 = new_entry(&key, &Addr::Ip("240.120.3.1".parse().unwrap()), 3000, 3010);
+        assert!(matches!(
+            table.add_entry(entry1.clone()),
+            AddEntryResult::Added
+        ));
+
+        assert!(matches!(table.add_entry(entry1), AddEntryResult::Exists));
+
+        let entry2 = new_entry(&key2, &Addr::Ip("240.120.3.2".parse().unwrap()), 3000, 3010);
+        assert!(matches!(
+            table.add_entry(entry2),
+            AddEntryResult::Restricted
+        ));
+
+        let mut key: [u8; 32] = [0; 32];
+
+        for i in 0..BUCKET_SIZE {
+            key[i] += 1;
+            let entry = new_entry(
+                &key,
+                &Addr::Ip(format!("127.0.{i}.1").parse().unwrap()),
+                3000,
+                3010,
+            );
+            table.add_entry(entry);
+        }
+
+        key[BUCKET_SIZE] += 1;
+        let entry = new_entry(&key, &Addr::Ip("125.20.0.1".parse().unwrap()), 3000, 3010);
+        assert!(matches!(table.add_entry(entry), AddEntryResult::Ignored));
+    }
+}
diff --git a/p2p/src/utils/mod.rs b/p2p/src/utils/mod.rs
new file mode 100644
index 0000000..e8ff9d0
--- /dev/null
+++ b/p2p/src/utils/mod.rs
@@ -0,0 +1,21 @@
+mod version;
+
+pub use version::{version_match, Version, VersionInt};
+
+use std::net::IpAddr;
+
+use karyons_net::Addr;
+
+/// Check if two addresses belong to the same subnet.
+pub fn subnet_match(addr: &Addr, other_addr: &Addr) -> bool {
+    match (addr, other_addr) {
+        (Addr::Ip(IpAddr::V4(ip)), Addr::Ip(IpAddr::V4(other_ip))) => {
+            // XXX Consider moving this to a different location
+            if other_ip.is_loopback() && ip.is_loopback() {
+                return false;
+            }
+            ip.octets()[0..3] == other_ip.octets()[0..3]
+        }
+        _ => false,
+    }
+}
diff --git a/p2p/src/utils/version.rs b/p2p/src/utils/version.rs
new file mode 100644
index 0000000..4986495
--- /dev/null
+++ b/p2p/src/utils/version.rs
@@ -0,0 +1,93 @@
+use std::str::FromStr;
+
+use bincode::{Decode, Encode};
+use semver::VersionReq;
+
+use crate::{Error, Result};
+
+/// Represents the network version and protocol version used in Karyons p2p.
+///
+/// # Example
+///
+/// ```
+/// use karyons_p2p::Version;
+///
+/// let version: Version = "0.2.0, >0.1.0".parse().unwrap();
+///
+/// let version: Version = "0.2.0".parse().unwrap();
+///
+/// ```
+#[derive(Debug, Clone)]
+pub struct Version {
+    pub v: VersionInt,
+    pub req: VersionReq,
+}
+
+impl Version {
+    /// Creates a new Version
+    pub fn new(v: VersionInt, req: VersionReq) -> Self {
+        Self { v, req }
+    }
+}
+
+#[derive(Debug, Decode, Encode, Clone)]
+pub struct VersionInt {
+    major: u64,
+    minor: u64,
+    patch: u64,
+}
+
+impl FromStr for Version {
+    type Err = Error;
+
+    fn from_str(s: &str) -> Result<Self> {
+        let v: Vec<&str> = s.split(", ").collect();
+        if v.is_empty() || v.len() > 2 {
+            return Err(Error::ParseError(format!("Invalid version{s}")));
+        }
+
+        let version: VersionInt = v[0].parse()?;
+        let req: VersionReq = if v.len() > 1 { v[1] } else { v[0] }.parse()?;
+
+        Ok(Self { v: version, req })
+    }
+}
+
+impl FromStr for VersionInt {
+    type Err = Error;
+
+    fn from_str(s: &str) -> Result<Self> {
+        let v: Vec<&str> = s.split('.').collect();
+        if v.len() < 2 || v.len() > 3 {
+            return Err(Error::ParseError(format!("Invalid version{s}")));
+        }
+
+        let major = v[0].parse::<u64>()?;
+        let minor = v[1].parse::<u64>()?;
+        let patch = v.get(2).unwrap_or(&"0").parse::<u64>()?;
+
+        Ok(Self {
+            major,
+            minor,
+            patch,
+        })
+    }
+}
+
+impl std::fmt::Display for VersionInt {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}.{}.{}", self.major, self.minor, self.patch)
+    }
+}
+
+impl From<VersionInt> for semver::Version {
+    fn from(v: VersionInt) -> Self {
+        semver::Version::new(v.major, v.minor, v.patch)
+    }
+}
+
+/// Check if a version satisfies a version request.
+pub fn version_match(version_req: &VersionReq, version: &VersionInt) -> bool {
+    let version: semver::Version = version.clone().into();
+    version_req.matches(&version)
+}