Let's say you want to make a real-time game, perhaps a 2D topdown game.
Things you would do in the game to keep it simple are:
- Connect to the server
- Move the player with the keys
- Possibly press space bar to attack
- Send a chat message
But what would happen if a datagram from any of these situations get lost?
What would you do?
1. Connecting to the server .
If you send a UDP datagram to the server, the server would take your IP and port and then create a player
based on an ID it gives you, this it how it identifies you every time it receives a datagram from you.
But what if upon "connection" (not actually a connection, just a udp datagram that says 'make me a part of your server'), this initial datagram gets lost. Is it right to say that you would just resend it if after a certain period of time you did not receive a reply back from the server?
2. Moving the player/attacking
If at any time we move the player/press a movement key/attack key, we would send a keystroke
to the server telling it what key we pressed/released.
The server would then relay this to all the other clients.
But what if this keystroke datagram gets lost? Either upon client->server or server->clients.
Because keystrokes are happening all the time, is it efficient to just resend it all the time?
Or would we just ignore the fact that it got lost along the way because there's a chance that if you press a key again it will most likely make it the next time?
3. Sending a chat message
This would be something that MUST reach the server.
If it got lost along the way, after a certain period of time if we did not receive a reply from the other side/receiving end, do we re-send it?
Is it okay to just keep resending datagrams if we know after a certain period of time it did not reach?
And also, what about confirming if a datagram got successfully sent?
If client sends a chat message to the server, and the server receives it, should the server send a reply back to the client to confirm that it received it? What would happen if that reply got lost, what then?