diff --git a/crates/engineioxide/src/socket.rs b/crates/engineioxide/src/socket.rs
index 222e3d8f..33be44f3 100644
--- a/crates/engineioxide/src/socket.rs
+++ b/crates/engineioxide/src/socket.rs
@@ -539,6 +539,10 @@ where
         s
     }
 
+    pub async fn close_internal_rx(self: Arc<Self>) {
+        self.internal_rx.lock().await.close();
+    }
+
     /// Create a dummy socket for testing purpose with a
     /// receiver to get the packets sent to the client
     pub fn new_dummy_piped(
diff --git a/crates/socketioxide/src/client.rs b/crates/socketioxide/src/client.rs
index e4ac7bfd..674bf771 100644
--- a/crates/socketioxide/src/client.rs
+++ b/crates/socketioxide/src/client.rs
@@ -113,6 +113,67 @@ impl<A: Adapter> Client<A> {
         }
     }
 
+    //just add latency to connect for test purpose
+    #[cfg(feature = "__test_harness")]
+    #[allow(unused)]
+    fn sock_connect_for_test(
+        self: &Arc<Self>,
+        auth: Option<Value>,
+        ns_path: &str,
+        esocket: &Arc<engineioxide::Socket<SocketData<A>>>,
+    ) {
+        #[cfg(feature = "tracing")]
+        tracing::debug!("auth: {:?}", auth);
+        let protocol: ProtocolVersion = esocket.protocol.into();
+        let connect = async move |ns: Arc<Namespace<A>>, esocket: Arc<EIoSocket<SocketData<A>>>| {
+            // add latency to connect
+            tokio::time::sleep(tokio::time::Duration::from_secs(3)).await;
+            if ns.connect(esocket.id, esocket.clone(), auth).await.is_ok() {
+                // cancel the connect timeout task for v5
+                if let Some(tx) = esocket.data.connect_recv_tx.lock().unwrap().take() {
+                    tx.send(()).ok();
+                }
+            }
+        };
+
+        if let Some(ns) = self.get_ns(ns_path) {
+            tokio::spawn(connect(ns, esocket.clone()));
+        } else if let Ok(Match { value: ns_ctr, .. }) = self.router.read().unwrap().at(ns_path) {
+            let path = Str::copy_from_slice(ns_path);
+            let ns = ns_ctr.get_new_ns(path.clone(), &self.adapter_state, &self.config);
+            let this = self.clone();
+            let esocket = esocket.clone();
+            let adapter = ns.adapter.clone();
+            let on_success = move || {
+                this.nsps.write().unwrap().insert(path, ns.clone());
+                tokio::spawn(connect(ns, esocket));
+            };
+            // We "ask" the adapter implementation to manage the init response itself
+            socketioxide_core::adapter::Spawnable::spawn(adapter.init(on_success));
+        } else if protocol == ProtocolVersion::V4 && ns_path == "/" {
+            #[cfg(feature = "tracing")]
+            tracing::error!(
+                "the root namespace \"/\" must be defined before any connection for protocol V4 (legacy)!"
+            );
+            esocket.close(EIoDisconnectReason::TransportClose);
+        } else {
+            let path = Str::copy_from_slice(ns_path);
+            let packet = self
+                .parser()
+                .encode(Packet::connect_error(path, "Invalid namespace"));
+            let _ = match packet {
+                Value::Str(p, _) => esocket.emit(p).map_err(|_e| {
+                    #[cfg(feature = "tracing")]
+                    tracing::error!("error while sending invalid namespace packet: {}", _e);
+                }),
+                Value::Bytes(p) => esocket.emit_binary(p).map_err(|_e| {
+                    #[cfg(feature = "tracing")]
+                    tracing::error!("error while sending invalid namespace packet: {}", _e);
+                }),
+            };
+        }
+    }
+
     /// Propagate a packet to its target namespace
     fn sock_propagate_packet(&self, packet: Packet, sid: Sid) -> Result<(), Error> {
         if let Some(ns) = self.get_ns(&packet.ns) {
@@ -426,6 +487,7 @@ mod test {
     use tokio::sync::mpsc;
 
     use crate::adapter::LocalAdapter;
+    use std::time::Duration;
     const CONNECT_TIMEOUT: std::time::Duration = std::time::Duration::from_millis(50);
 
     fn create_client() -> Arc<super::Client<LocalAdapter>> {
@@ -490,4 +552,50 @@ mod test {
             .await
             .unwrap_err();
     }
+    #[derive(Debug, Clone)]
+    struct MockConnectTimeoutHandler(Arc<super::Client<LocalAdapter>>);
+
+    impl EngineIoHandler for MockConnectTimeoutHandler {
+        type Data = <Client<LocalAdapter> as engineioxide::handler::EngineIoHandler>::Data;
+
+        fn on_connect(self: Arc<Self>, socket: Arc<EIoSocket<Self::Data>>) {
+            socket.data.io.set(SocketIo::from(self.0.clone())).ok();
+
+            self.0.sock_connect_for_test(None, "/", &socket);
+        }
+
+        fn on_disconnect(&self, socket: Arc<EIoSocket<Self::Data>>, reason: EIoDisconnectReason) {
+            self.0.clone().on_disconnect(socket, reason);
+        }
+
+        fn on_message(self: &Arc<Self>, msg: Str, socket: Arc<EIoSocket<Self::Data>>) {
+            self.0.clone().on_message(msg, socket);
+        }
+
+        fn on_binary(self: &Arc<Self>, data: Bytes, socket: Arc<EIoSocket<Self::Data>>) {
+            self.0.clone().on_binary(data, socket);
+        }
+    }
+
+    #[tokio::test]
+    async fn should_not_reserve_socket_if_connect_time_out() {
+        let client = create_client();
+        let client = Arc::new(MockConnectTimeoutHandler(client));
+        let sid = Sid::new();
+        let sock = EIoSocket::new_dummy(sid, Box::new(move |_, _| {}));
+        // connect to ns but spawned fn `connect` will be stuck
+        client.clone().on_connect(sock.clone());
+        //spawned fn `connect` is stuck ,so client don't keep heartbeat
+        client
+            .clone()
+            .on_disconnect(sock.clone(), EIoDisconnectReason::HeartbeatTimeout);
+        //equal to engineio.close_session(_,_)
+        sock.close_internal_rx().await;
+        //wait for spawned fn `connect(crates/socketioxide/src/client.rs:129)` finish
+        tokio::time::sleep(Duration::from_secs(4)).await;
+        let guard = client.0.nsps.read().unwrap();
+        let ns = guard.get("/").unwrap();
+        // ns should not reserve socket
+        assert!(ns.get_socket(sid).is_err());
+    }
 }
diff --git a/crates/socketioxide/src/ns.rs b/crates/socketioxide/src/ns.rs
index 51365cc6..221a7d95 100644
--- a/crates/socketioxide/src/ns.rs
+++ b/crates/socketioxide/src/ns.rs
@@ -134,6 +134,15 @@ impl<A: Adapter> Namespace<A> {
             #[cfg(feature = "tracing")]
             tracing::debug!("error sending connect packet: {:?}, closing conn", _e);
             esocket.close(engineioxide::DisconnectReason::PacketParsingError);
+            // also remove sid inserted before
+            self.sockets
+                .write()
+                .map_err(|_| {
+                    #[cfg(feature = "tracing")]
+                    tracing::debug!("get lock err for {sid}");
+                    ConnectFail
+                })?
+                .remove(&sid);
             return Err(ConnectFail);
         }