Socket.IO allows you to “namespace” your sockets, which essentially means assigning different endpoints or paths. This is a useful feature to minimize the number of resources (TCP connections) and at the same time separate concerns within your application by introducing separation between communication channels. Default namespace We call the default namespace / and it’s the one Socket.IO clients connect to by default, and the one the server listens to by default. This namespace is identified by

Server#listen Synonym of Server#attach.

Socket#emit(name:String[, …]):Socket Emits an event to the socket identified by the string name. Any other parameters can be included. All datastructures are supported, including Buffer. JavaScript functions can’t be serialized/deserialized. var io = require('socket.io')(); io.on('connection', function(socket){ socket.emit('an event', { some: 'data' }); });

Socket#leave(name:String[, fn:Function]):Socket Removes the socket from room, and fires optionally a callback fn with err signature (if any). Rooms are left automatically upon disconnection. The mechanics of leaving rooms are handled by the Adapter that has been configured (see Server#adapter above), defaulting to socket.io-adapter.

Socket#join(name:String[, fn:Function]):Socket Adds the socket to the room, and fires optionally a callback fn with err signature (if any). The socket is automatically a member of a room identified with its session id (see Socket#id). The mechanics of joining rooms are handled by the Adapter that has been configured (see Server#adapter above), defaulting to socket.io-adapter.

Socket#in(room:String):Socket Sets a modifier for a subsequent event emission that the event will only be broadcasted to sockets that have joined the given room. To emit to multiple rooms, you can call to several times. var io = require('socket.io')(); io.on('connection', function(socket){ socket.to('others').emit('an event', { some: 'data' }); });

Socket.IO is now completely instrumented by a minimalistic yet tremendously powerful utility called debug by TJ Holowaychuk. Before 1.0, the Socket.IO server would default to logging everything out to the console. This turned out to be annoyingly verbose for many users (although extremely useful for others), so now we default to being completely silent by default. The basic idea is that each module used by Socket.IO provides different debugging scopes that give you insight into the internals. B