CODE EXAMPLE FOR JAVASCRIPT

socket io emit to specific client

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").to("room2").emit(/* ... */);

  // to all clients in room1
  io.in("room1").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(/* ... */);

});