javascript - 当客户端调用断开连接时，Socket.io 服务器未收到 'disconnect' 事件

Question

我正在node.js(客户端和服务器)上使用socket.io，并且在“断开连接”事件方面遇到问题。看一下下面的摩卡测试代码:

it('This test never finishes', function(done) {
  // Output:
  // connected socket iYTGdwMJ0yVM5orGAAAB

  io.on('connection', (socket) => {
    console.log('connected socket', socket.id);
    socket.on('disconnect', () => {
      console.log('io disconnect');
      done();
    });
  });

  const mj = ioClient(`https://localhost:${socketPort}`);

  mj.on('disconnect', () => {
    console.log('mj disconnect');
  });

  mj.disconnect();
});

it('This test works', function(done) {
  // Output:
  // connected socket DNUREuytEp1CPJdFAAAC
  // io disconnect

  io.on('connection', (socket) => {
    console.log('connected socket', socket.id);
    console.log(io.socket.connected);
    socket.on('disconnect', () => {
      console.log('io disconnect');
      done();
    });
    socket.disconnect();
  });

  const mj = ioClient(`https://localhost:${socketPort}`);

  mj.on('disconnect', () => {
    console.log('mj disconnect');
  });

  // Looks like this has no effect
  mj.disconnect();
});

当客户端调用disconnect时，为什么服务端没有触发socket.on('disconnect', ...)监听器？

Answer 1

我认为这是一个典型的同步性问题(阅读代码注释中的解释)。

// This code will try to connect the server - 
// but the connection process is asynchronous
const mj = ioClient(`https://localhost:${socketPort}`);

// Now you subscribe to the disconnect event which is fine
mj.on('disconnect', () => {
    console.log('mj disconnect');
});

// And now you try to disconnect immediately which is done synchronously
// but how do you want to disconnect since you are still not connected ...
mj.disconnect();

您可以做的是在确保已连接后尝试断开连接:)

const mj = ioClient(`https://localhost:${socketPort}`);

mj.on('connect', () => {

    // Subscribe to disconnect event once you know you are connected
    mj.on('disconnect', () => {
        console.log('mj disconnect');
    });

    // Now disconnect once you are connected 
    mj.disconnect();
});