socketclient add debug setting

lib/im/SocketClient.dart

@@ -70,7 +70,10 @@ class SocketClient {
       Uint8List data = utf8.encode(jsonEncode({"heartbeat": milliseTime}));
       MsgData msgData = MsgData(from: userId, type: MsgType.TEXT, data: data);
       final proto2 = Proto(3, 1, msgData.writeToBuffer());
-      if(_socket != null)
+      if(!checkSocket()) {
+        timer.cancel();
+        return;
+      }
       _socket.add(proto2.toBytes());
     });
   }