diff --git a/.gitignore b/.gitignore
index 4565963..4c16996 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,4 @@ debian-build
 debian/.debhelper
 debian/debhelper-build-stamp
 .DS_Store
+.vscode
diff --git a/libs/hbb_common/protos/rendezvous.proto b/libs/hbb_common/protos/rendezvous.proto
index 2c5f1b3..1ac60f3 100644
--- a/libs/hbb_common/protos/rendezvous.proto
+++ b/libs/hbb_common/protos/rendezvous.proto
@@ -148,6 +148,15 @@ message PeerDiscovery {
   string misc = 7;
 }
 
+message OnlineRequest {
+  string id = 1;
+  repeated string peers = 2;
+}
+
+message OnlineResponse {
+  bytes states = 1;
+}
+
 message RendezvousMessage {
   oneof union {
     RegisterPeer register_peer = 6;
@@ -167,5 +176,7 @@ message RendezvousMessage {
     TestNatRequest test_nat_request = 20;
     TestNatResponse test_nat_response = 21;
     PeerDiscovery peer_discovery = 22;
+    OnlineRequest online_request = 23;
+    OnlineResponse online_response = 24;
   }
 }
diff --git a/src/rendezvous_server.rs b/src/rendezvous_server.rs
index 60f95d9..b93e04f 100644
--- a/src/rendezvous_server.rs
+++ b/src/rendezvous_server.rs
@@ -89,12 +89,7 @@ enum LoopFailure {
 
 impl RendezvousServer {
     #[tokio::main(flavor = "multi_thread")]
-    pub async fn start(
-        port: i32,
-        serial: i32,
-        key: &str,
-        rmem: usize,
-    ) -> ResultType<()> {
+    pub async fn start(port: i32, serial: i32, key: &str, rmem: usize) -> ResultType<()> {
         let (key, sk) = Self::get_server_sk(key);
         let addr = format!("0.0.0.0:{}", port);
         let addr2 = format!("0.0.0.0:{}", port - 1);
@@ -756,6 +751,39 @@ impl RendezvousServer {
         }
     }
 
+    #[inline]
+    async fn handle_online_request(
+        &mut self,
+        stream: &mut FramedStream,
+        peers: Vec<String>,
+    ) -> ResultType<()> {
+        let mut states = BytesMut::zeroed((peers.len() + 7) / 8);
+        for i in 0..peers.len() {
+            let peer_id = &peers[i];
+            // bytes index from left to right
+            let states_idx = i / 8;
+            let bit_idx = 7 - i % 8;
+            if let Some(peer) = self.pm.get_in_memory(&peer_id).await {
+                let (elapsed, _) = {
+                    let r = peer.read().await;
+                    (r.last_reg_time.elapsed().as_millis() as i32, r.socket_addr)
+                };
+                if elapsed < REG_TIMEOUT {
+                    states[states_idx] |= 0x01 << bit_idx;
+                }
+            }
+        }
+
+        let mut msg_out = RendezvousMessage::new();
+        msg_out.set_online_response(OnlineResponse {
+            states: states.into(),
+            ..Default::default()
+        });
+        stream.send(&msg_out).await?;
+
+        Ok(())
+    }
+
     #[inline]
     async fn send_to_tcp(&mut self, msg: RendezvousMessage, addr: SocketAddr) {
         let mut tcp = self.tcp_punch.lock().await.remove(&addr);
@@ -1014,8 +1042,8 @@ impl RendezvousServer {
     }
 
     async fn handle_listener2(&self, stream: TcpStream, addr: SocketAddr) {
+        let mut rs = self.clone();
         if addr.ip().to_string() == "127.0.0.1" {
-            let rs = self.clone();
             tokio::spawn(async move {
                 let mut stream = stream;
                 let mut buffer = [0; 64];
@@ -1033,34 +1061,31 @@ impl RendezvousServer {
             let mut stream = stream;
             if let Some(Ok(bytes)) = stream.next_timeout(30_000).await {
                 if let Ok(msg_in) = RendezvousMessage::parse_from_bytes(&bytes) {
-                    if let Some(rendezvous_message::Union::TestNatRequest(_)) = msg_in.union {
-                        let mut msg_out = RendezvousMessage::new();
-                        msg_out.set_test_nat_response(TestNatResponse {
-                            port: addr.port() as _,
-                            ..Default::default()
-                        });
-                        stream.send(&msg_out).await.ok();
+                    match msg_in.union {
+                        Some(rendezvous_message::Union::TestNatRequest(_)) => {
+                            let mut msg_out = RendezvousMessage::new();
+                            msg_out.set_test_nat_response(TestNatResponse {
+                                port: addr.port() as _,
+                                ..Default::default()
+                            });
+                            stream.send(&msg_out).await.ok();
+                        }
+                        Some(rendezvous_message::Union::OnlineRequest(or)) => {
+                            allow_err!(rs.handle_online_request(&mut stream, or.peers).await);
+                        }
+                        _ => {}
                     }
                 }
             }
         });
     }
 
-    async fn handle_listener(
-        &self,
-        stream: TcpStream,
-        addr: SocketAddr,
-        key: &str,
-        ws: bool,
-    ) {
+    async fn handle_listener(&self, stream: TcpStream, addr: SocketAddr, key: &str, ws: bool) {
         log::debug!("Tcp connection from {:?}, ws: {}", addr, ws);
         let mut rs = self.clone();
         let key = key.to_owned();
         tokio::spawn(async move {
-            allow_err!(
-                rs.handle_listener_inner(stream, addr, &key, ws)
-                    .await
-            );
+            allow_err!(rs.handle_listener_inner(stream, addr, &key, ws).await);
         });
     }
 
@@ -1080,10 +1105,7 @@ impl RendezvousServer {
             while let Ok(Some(Ok(msg))) = timeout(30_000, b.next()).await {
                 match msg {
                     tungstenite::Message::Binary(bytes) => {
-                        if !self
-                            .handle_tcp(&bytes, &mut sink, addr, key, ws)
-                            .await
-                        {
+                        if !self.handle_tcp(&bytes, &mut sink, addr, key, ws).await {
                             break;
                         }
                     }
@@ -1094,10 +1116,7 @@ impl RendezvousServer {
             let (a, mut b) = Framed::new(stream, BytesCodec::new()).split();
             sink = Some(Sink::TcpStream(a));
             while let Ok(Some(Ok(bytes))) = timeout(30_000, b.next()).await {
-                if !self
-                    .handle_tcp(&bytes, &mut sink, addr, key, ws)
-                    .await
-                {
+                if !self.handle_tcp(&bytes, &mut sink, addr, key, ws).await {
                     break;
                 }
             }