Socket.io在页面刷新上创建多个连接

Question

I am making a chatroom but after each page refresh, more connections are made. For example, if I go to my chat room page, only one connection is created. However, after I refresh once, 2 clients are now connected. After each page refresh, one more connection is added.

here is my chat route

    /* GET home page. */
router.get('/', accessControl.ensureAuthenticated, function(req, res, next) {
  const io = req.app.io;
  console.log('const io created');
  io.on('connection', function(socket){
    console.log(' %s sockets connected', io.engine.clientsCount);
    console.log('[NodeApp] (socket.io) A client has connected');
    socket.on('chat message', function(message){
      if (message.sessionID == req.session.id) {
        io.emit('chat message', message);
        console.log('message: ' + message.message);
      } else {
        console.log('client sessionID ('+message.sessionID+') does not match server sessionID ('+req.session.id+')');
      }
    });
    socket.on('disconnect', function(){
      console.log('[NodeApp] (socket.io) A client has disconnected');
      socket.disconnect();
    });
  });

  res.render('chat/index', {
    title: "Chat",
    //send session id for client verification
    sessionID: req.session.id,
  });
});

the output after refreshing the chat page 3 times:

const io created
1 sockets connected
[NodeApp] (socket.io) A client has connected
const io created
[NodeApp] (socket.io) A client has disconnected
1 sockets connected
[NodeApp] (socket.io) A client has connected
1 sockets connected
[NodeApp] (socket.io) A client has connected
const io created
[NodeApp] (socket.io) A client has disconnected
[NodeApp] (socket.io) A client has disconnected
1 sockets connected
[NodeApp] (socket.io) A client has connected
1 sockets connected
[NodeApp] (socket.io) A client has connected
1 sockets connected
[NodeApp] (socket.io) A client has connected
message: test message (should be sent 3 times)
message: test message (should be sent 3 times)
message: test message (should be sent 3 times)

Answer 1

You can't put this:

io.on('connection', function(socket){...}

inside a route handler. Every time that route is hit, you create yet another listener for the event, so they pile up with lots of duplicates and thus you process each message multiple times in all those duplicate event handlers.

You need to put that outside any route handler. The socket.io server and its listeners needs to be configured when you configured your socket.io server, not in a route handler.