Release event handlers on disconnection of Socket.IO client

问题

I'm using Socket.IO like in this sample:

io.sockets.on("connection", function (socket) {

    myService.on("myevent", function() {
        socket.emit("myevent", { /* ... */ });
        // some stuff happens here of course
    });

});

myService is a singleton and a subclass of EventEmitter which triggers the myevent over the time. Anything works fine, however I guess that I create some kind of leak in this case. How does my service know that it doesn't need to call the handler once the connection is destroyed? Is there some kind of destroy event I can catch and then remove the handler from myService?

回答1:

Listen to the socket disconnect event and when you get a disconnect event, remove the relevant event handler from the myService object.

You should be able to do that like this:

io.sockets.on("connection", function (socket) {

    function handler() {
        socket.emit("myevent", { /* ... */ });
        // some stuff happens here of course
    }

    myService.on("myevent", handler);

    socket.on("disconnect", function() {
        myService.removeListener("myevent", handler);
    });

});

If what you're trying to do is to broadcast to all connected sockets, you could just install one "myevent" listener (not one per connection) and use io.emit() to broadcast to all sockets too and not have to handle the connect or disconnect events for this purpose.

回答2:

If you are planning to send data to all sockets when some other event fires, you don't need to add/remove another listeners every time a client connects/disconnects.

It is a lot more efficient and easier to simply fire the socket.io event to all sockets that are connected right now using io.sockets (which is a reference to the default namespace with all clients on it by default) and io.sockets.emit:

myService.on('myevent', () => {
  io.sockets.emit('myevent', {/*...*/});
});

If you only need to fire this event to some subset of your users, try using specific namespaces or rooms:

myService.on('myevent', () => {

  //with namespaces
  io.of('namespace').emit('myevent', {/*...*/});

  //with rooms
  io.to('room').emit('myevent', {/*...*/});

});

来源：https://stackoverflow.com/questions/28773807/release-event-handlers-on-disconnection-of-socket-io-client

标签

javascript

node.js

Socket.IO