Online 2 Player Snake

Server

Author: Tyler Black

The server program for 2 player snake game (client repo found here). SnakeServer is a lightweight websocket server that hosts a 2 player snake match.

The server is a stateful and authoritative but tick-less. The client sends all updates to the server, and the server handles all logic. However, the client does hold the tick state, and the overall game state. Since snake is a low tick and simple game, there is no tick verification or latency prediction.

Architecture

By binding to $0.0.0.0:9001$, the server accepts connections on all network interfaces. This allows multiple server deployments, and each server instance is capable of hosting many simultaneous games.

Message Protocol

Messages are sent as JSON code and payload pairs. All server-client communication is handled by one of these messages.

NOTES:

• Payloads are sent as strings, and coordinates are sent as x,y pairs, with no spaces.
• NULL payloads do not matter—usually sent as 0.

To Client

Code	Payload	Description
SEAT	—	—
START	player	Both users connected, start app (before set, first message)
COLLISION	player	Snake collided
APPLE	x,y	Sends new apple coordinates
GROW	player	Tells client that a player should grow
SCORE	s1,s2	Sends updated scores for both players
SET	—	Both players ready, start game
DISCONNECT	player	Notifies that a player disconnected

Both Directions

Code	Payload	Description
MOVE	x,y	Movement update (player → server, server → client)

To Server

Code	Payload	Description
READY	—	Client indicates it is ready to start game
RESET	—	Client requests a full game reset

Build

The server is built using cmake and uses a single dependency.

Prerequisites

• vcpkg to install unofficial-uwebsockets (v20.74.0)
  • (alternate option) install manually $\mu$websockets
    • must change include_directories and link_libraries in CMakeLists.txt
• CMake >3.31
• C++23 Compiler
• MacOS or Linux
  • (Windows should work, but untested)

1. Install prerequisites
2. Generate build using CMake (be sure to set your paths in the script below):

    mkdir -p build
    cd build

    cmake .. \
    -DCMAKE_BUILD_TYPE=Release \
    -DCMAKE_TOOLCHAIN_FILE=/path/to/vcpkg/scripts/buildsystems/vcpkg.cmake

3. Compile:

  cmake --build . -j$

4. Run:

  ./SnakeServer