socket.io - works first time, not second time onwards

Question

When I start my node.js server and client gets connected, I am able to send a request from client (socket.emit) and get a response (socket.on('rentsAround'....)). But when I connect 2nd time onwards, the client is able to send, but server can not send or emit. So I have to restart the server again. I understand that it is working as expected, but somehow my understanding is wrong somewhere... Would someone please point out.

client side: ========

    var socket = new io.Socket();
    socket = io.connect();

    socket.on('rentsAround', function(data){
        registration.handleRentsAround(data);
    });


    socket.on('locationDetailsRes', function(data){
        registration.handleRentsAround(data);
    });

    socket.on('connect', function(data){
        alert('inside connect on client side');
    });

socket.on('disconnect', function(){ 
    // do something, if you want to. 
    });
    .............
    socket.emit("searchRent",  {"lat":lat, "lng":lng});

server side: ========

socket.sockets.on('connection', function(client){ 

            client.on('searchRent', function(msg){
        console.log('inside on connection');
                // do something and reply back
        client.emit('rentsAround',{"totalRents":docs.length, "rents":docs});
            });

   client.on('disconnect', function(){ 
        sys.puts("client disconnect"); 
        mongoose.disconnect();
        }); 

Answer 1

Socket.io 0.7 onwards will try and reuse connections to the same host. In my experience I've found this behaviour can be a little flakey.

I can't tell from the small code sample you provided, but I suspect the problem is that the second call to connect() is trying to reuse the first (closed) connection.

The workaround is to pass the 'force new connection' option when you call connect(). Eg:

io.connect("http://localhost", {'force new connection': true});

Answer 2

Your second line discards the object created in the first line. Simply doing this should work:

var socket = io.connect();

The problem with first send and second fail could be due to browser/protocol. I have seen such behaviour with Internet Explorer and XHR transport, and also with Opera using JSONP.

If you are using IE, try switching to JSONP and it should work properly. This can be done on the server side, by supplying the transport list to configuration. Just make sure JSONP comes before XHR. Something like this:

sio.set('transports', [
    'websocket'
    , 'flashsocket'
    , 'jsonp-polling'
    , 'xhr-polling'
    , 'htmlfile'
]);

Answer 3

As of socket.io 1.0, two settings control this behaviour:

• "force new connection":true, on the client connect() call.

• "cookie":false, on the server Server() constructor.

Apparently, both produce the exact same behaviour.

The second method is, as of today, undocumented. However, looking at the source code you can see that all options passed to socket.io Server() are passed to the internal Engine.io library Server() constructor, which lets you change any of the options there. These options are documented here:

https://github.com/LearnBoost/engine.io