How to produce messages with packet type id like 420 430

[Al3x4n]

How to produce messages with packet type id like 420 430?
I do send cmd from server to socket.io client like this but nothing response
socket.send("start", start_cmd.toString(), new SocketIoSocket.ReceivedByRemoteAcknowledgementCallback() {
@OverRide
public void onReceivedByRemote(Object... os) {
System.out.println("Start cmd response: " + os);
}
});

But when I use this cmd, client does received (without callback)
socket.send("start", start_cmd.toString())