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Version: 2.x

Emit cheatsheet

io.on('connection', onConnect);

function onConnect(socket){

// sending to the client
socket.emit('hello', 'can you hear me?', 1, 2, 'abc');

// sending to all clients except sender
socket.broadcast.emit('broadcast', 'hello friends!');

// sending to all clients in 'game' room except sender'game').emit('nice game', "let's play a game");

// sending to all clients in 'game1' and/or in 'game2' room, except sender'game1').to('game2').emit('nice game', "let's play a game (too)");

// sending to all clients in 'game' room, including sender'game').emit('big-announcement', 'the game will start soon');

// sending to all clients in namespace 'myNamespace', including sender
io.of('myNamespace').emit('bigger-announcement', 'the tournament will start soon');

// sending to a specific room in a specific namespace, including sender
io.of('myNamespace').to('room').emit('event', 'message');

// sending to individual socketid (private message)'hey', 'I just met you');

// WARNING: `` will NOT work, as it will send to everyone in the room
// named `` but the sender. Please use the classic `socket.emit()` instead.

// sending with acknowledgement
socket.emit('question', 'do you think so?', function (answer) {});

// sending without compression
socket.compress(false).emit('uncompressed', "that's rough");

// sending a message that might be dropped if the client is not ready to receive messages
socket.volatile.emit('maybe', 'do you really need it?');

// specifying whether the data to send has binary data
socket.binary(false).emit('what', 'I have no binaries!');

// sending to all clients on this node (when using multiple nodes)
io.local.emit('hi', 'my lovely babies');

// sending to all connected clients
io.emit('an event sent to all connected clients');


Note: The following events are reserved and should not be used as event names by your application:

  • connect
  • connection
  • connect_error
  • connect_timeout
  • error
  • disconnect
  • disconnecting
  • newListener
  • reconnect_attempt
  • reconnecting
  • reconnect_error
  • reconnect_failed
  • removeListener
  • ping
  • pong