ace-of-shades-2/design/net.md

AOS-2 Network Protocol

This document describes the network protocol used by Ace of Shades 2 for server-client communication.

All communications, whether they be UDP or TCP, use the record-net library for sending packets as serialized records.

When referring to the names of packets, we will assume a common package name of nl.andrewl.aos_core.net.

Player Connection

This workflow is involved in the establishment of a connection between the client and server.

1. Player sends a ConnectRequestMessage via TCP, immediately upon opening a socket connection. It contains the player's desired username, and their udpPort that they will use to connect.
2. The server will respond with either a ConnectRejectMessage with a reason for the rejection, or a ConnectAcceptMessage.
3. If the player received an acceptance message, they will then send a DatagramInit to the server's UDP socket (on the same address/port). The player should keep sending such an init message until they receive a DatagramInit message echoed back as a response. The player should then stop sending init messages, and expect to begin receiving normal communication data through the datagram socket.

World Data

A combination of TCP and UDP communication is used to ensure that all connected clients have the latest information about the state of the world.

Initially when the player connects to a server, the server will begin sending ChunkDataMessage packets via TCP to the player, with the full chunk data of an individual chunk.

If, during the course of a game tick, a chunk is updated, at the end of the tick, a ChunkUpdateMessage message is sent which provides the coordinates and new block data for a block in a chunk.

A player should regularly send a ChunkHashMessage to the server that contains a hash of a certain chunk, to verify that the player's chunk data matches the server's. The server will send a ChunkDataMessage if the player's hash is incorrect and the player should replace their chunk data.