Emit cheatsheet

Server-side

io.on("connection", (socket) => {
  // basic emit  socket.emit(/* ... */);
  // to all clients in the current namespace except the sender  socket.broadcast.emit(/* ... */);
  // to all clients in room1 except the sender  socket.to("room1").emit(/* ... */);
  // to all clients in room1 and/or room2 except the sender  socket.to(["room1", "room2"]).emit(/* ... */);
  // to all clients in room1  io.in("room1").emit(/* ... */);
  // to all clients in room1 and/or room2 except those in room3  io.to(["room1", "room2"]).except("room3").emit(/* ... */);
  // to all clients in namespace "myNamespace"  io.of("myNamespace").emit(/* ... */);
  // to all clients in room1 in namespace "myNamespace"  io.of("myNamespace").to("room1").emit(/* ... */);
  // to individual socketid (private message)  io.to(socketId).emit(/* ... */);
  // to all clients on this node (when using multiple nodes)  io.local.emit(/* ... */);
  // to all connected clients  io.emit(/* ... */);
  // WARNING: `socket.to(socket.id).emit()` will NOT work, as it will send to everyone in the room  // named `socket.id` but the sender. Please use the classic `socket.emit()` instead.
  // with acknowledgement  socket.emit("question", (answer) => {    // ...  });
  // without compression  socket.compress(false).emit(/* ... */);
  // a message that might be dropped if the low-level transport is not writable  socket.volatile.emit(/* ... */);
  // with timeout  socket.timeout(5000).emit("my-event", (err) => {    if (err) {      // the other side did not acknowledge the event in the given delay    }  });});

Client-side

// basic emitsocket.emit(/* ... */);
// with acknowledgementsocket.emit("question", (answer) => {  // ...});
// without compressionsocket.compress(false).emit(/* ... */);
// a message that might be dropped if the low-level transport is not writablesocket.volatile.emit(/* ... */);
// with timeoutsocket.timeout(5000).emit("my-event", (err) => {  if (err) {    // the other side did not acknowledge the event in the given delay  }});

Reserved events

On each side, the following events are reserved and should not be used as event names by your application:

• connect
• connect_error
• disconnect
• disconnecting
• newListener
• removeListener

// BAD, will throw an errorsocket.emit("disconnecting");