diff --git a/src/rtmt/rtmt.ts b/src/rtmt/rtmt.ts
index 00c41cc..aa8ccdf 100644
--- a/src/rtmt/rtmt.ts
+++ b/src/rtmt/rtmt.ts
@@ -1,7 +1,8 @@
 export type Bytes = Buffer
-export type OnMessage = (clientID : string, message : Object) => any
+export type OnMessage = (clientID: string, message: Object) => any
 
-export interface RTMT{
-    sendMessage : (clientID : string, channel : string, message : Object) => any
-    listenMessage : (channel : string, callback : OnMessage) => any
+export interface RTMT {
+    sendMessage: (clientID: string, channel: string, message: Object) => any;
+    listenMessage: (channel: string, callback: OnMessage) => any;
+    isClientOnline(clientID: string): boolean;
 }
\ No newline at end of file
diff --git a/src/rtmt/rtmt_websocket.ts b/src/rtmt/rtmt_websocket.ts
index 46e58fd..bb84d7f 100644
--- a/src/rtmt/rtmt_websocket.ts
+++ b/src/rtmt/rtmt_websocket.ts
@@ -126,4 +126,10 @@ export class RTMTWS implements RTMT {
         //@ts-ignore
         ws.isAlive = true;
     }
+    
+    isClientOnline(clientID: string): boolean {
+        const ws = this.clients.has(clientID);
+        //@ts-ignore
+        return ws && ws.isAlive;
+    }
 }
\ No newline at end of file