Websocket - sockjs - InvalidStateError：连接尚未建立

Question

When using stomp.js and sockjs from within Javascript, I can connect well with a Spring Boot backend.

When using stompjs and sockjs from with Angular5, I keep on getting these errors:

InvalidStateError: The connection has not been established yet

Is there a workaround? Just adding the sockjs.min.js, as mentioned in this post , was not helping.

The detailed log is:

Setting up connection/1 main.3388a5e3a20e64e3bdb8.bundle.js:1 Setting up connection/2 main.3388a5e3a20e64e3bdb8.bundle.js:1 Going to subscribe ... main.3388a5e3a20e64e3bdb8.bundle.js:1 Opening Web Socket... main.3388a5e3a20e64e3bdb8.bundle.js:1 >>> SEND destination:/app/chat.addUser content-length:29

{"sender":"me","type":"JOIN"} main.3388a5e3a20e64e3bdb8.bundle.js:1 ERROR Error: Uncaught (in promise): Error: InvalidStateError: The connection has not been established yet Error: InvalidStateError: The connection has not been established yet at r.send (scripts.d6f701ecf84f24372966.bundle.js:1)

My code in Angular (translated from Javascript) is:

 let ws = new SockJS(this.serverUrl);
    this.stompClient = Stomp.over(ws);
    let that = this;
    console.log('Setting up connection/2');
    console.log('Going to subscribe ... ');
    this.stompClient.connect({}, function (frame) {
      console.log('Going to subscribe ... ');
      that.stompClient.subscribe('/topic/public', (payload) => {
          console.log('Subscribe: Incoming message: ' + payload.body);
          if (payload.body) {
            let message = JSON.parse(payload.body);
            if (message.sender === 'MyBot') {
              this.createAndAddChat('you', message.content);
            } else {
              this.createAndAddChat('me', message.content);
            }
            console.log('New message arrived: ' + payload.body);
          }
        },
        error => {
          console.log( 'Subscribe: error: ' + error)
        },
        () => {
         console.log( 'Subscribe, On complete')
        });
    });
    this.stompClient.send("/app/chat.addUser", {},
      JSON.stringify({sender: 'me', type: 'JOIN'})
    )

Answer 1

The send method is now called directly after starting (!) the asynchronous get-connection call. That's wrong.

There are 2 solutions:

• Good: Put the send call within the async-body of the get-connection. So after the connection is made, call the send method.
• Not optimal: Wait for some time to have the async get-connection to complete.

Answer 2

    stompClient.connect({}, function (frame) {
        console.log('Connected: ' + frame);
        setTimeout(function() {
           stompClient.subscribe("/topic/mytopic/", function (message) {
              showDeviceConnection(deviceIds[i], message.body);
           });
        }, 500);});