在Angular的Socket.io房间中无法接收消息

Question

我正在尝试使用socket.io创建一个房间以便在我的网站上聊天。

不幸的是，即使消息发送正确并且两个用户都加入了同一个房间，也不会收到消息。

到目前为止，这是我的代码：

chat.component.ts：

// both users joining the same room with their matchId
// __________________________________________________________________

joinRoom(matchId) {
  try {
    this.socket = io.connect('http://localhost:3000');
    this.socket.emit('join room', matchId.toString());
  } catch (e) {
   console.log('Could not connect socket.io');
  }
}


// emiting the message object
// __________________________________________________________________

this.socket.emit('send message', obj);


// receiving the message object and pushing it to the messageList
// __________________________________________________________________

receive = (obj) => {
  if (obj) {
    this.messageList.push(obj);
  }
}

ngOnInit() {
  try {
    this.socket.on('receive message', this.receive);
  } catch (e) {
    console.log('Could not connect socket.io');
  }
}

backend：

io.sockets.on('connection', function(socket) {
  var roomId;
  socket.on('join room', function(room) {
    socket.join(room);
    console.log('a user connected to room', room);
    roomId = room;
  });
  socket.on('send message', (obj) => {
    socket.broadcast.to(roomId).emit('receive message', obj);
  });
});

我同时收到join room和send message事件。

我该怎么办才能在房间里接收消息？

谢谢！