TigerEmu/Networking/Game/WebSocketServer.cs

using System.Net;
using System.Net.WebSockets;
using Tiger.Communication.Messages;
using Tiger.Communication.Messages.Types;
using Tiger.Networking.Game.Sessions;
using Tiger.Utils;

namespace Tiger.Networking.Game;

public class WebSocketServer : IWebSocketServer
{
    private readonly HttpListener _httpListener = new();
    private readonly IGameSessionManager _gameSessionManager;
    private readonly IMessageHandler _messageHandler;

    public WebSocketServer(IGameSessionManager gameSessionManager, IMessageHandler messageHandler)
    {
        _gameSessionManager = gameSessionManager;
        _messageHandler = messageHandler;
    }

    public async Task Start(string uriPrefix)
    {
        _httpListener.Prefixes.Add(uriPrefix);
        _httpListener.Start();

        Console.WriteLine($"Listening on {uriPrefix}...");

        while (true)
        {
            var context = await _httpListener.GetContextAsync();

            if (context.Request.IsWebSocketRequest)
            {
                ProcessRequestAsync(context);
            }
            else
            {
                context.Response.StatusCode = 400;
                context.Response.Close();
            }
        }
    }

    private async void ProcessRequestAsync(HttpListenerContext context)
    {
        WebSocket? webSocket = null;

        try
        {
            var webSocketContext = await context.AcceptWebSocketAsync(null);
            webSocket = webSocketContext.WebSocket;

            var session = _gameSessionManager.AddSession(webSocket);
            Console.WriteLine($"WebSocket Session {session.SessionId} has connected.");

            await ReceiveMessageAsync(session.SessionId);
        }
        catch (Exception e)
        {
            Console.WriteLine($"WebSocket Session Error: {e.Message}");
        }
        finally
        {
            if (webSocket != null)
            {
                _gameSessionManager.RemoveSession(webSocket);
                webSocket.Dispose();
            }
        }
    }
    
    private async Task ReceiveMessageAsync(string sessionId)
    {
        var buffer = new byte[1024 * 4];
        while (_gameSessionManager.GetSession(sessionId) is { WebSocket.State: WebSocketState.Open } gameSession)
        {
            var result = await gameSession.WebSocket.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);
            var offset = 0;
            
            while (result.MessageType == WebSocketMessageType.Binary && offset + 4 <= result.Count)
            {
                var length = ByteUtils.GetInt32(new[]
                {
                    buffer[offset], buffer[offset + 1], buffer[offset + 2], buffer[offset + 3]
                });
                offset += 4;

                if (offset + length > result.Count) break;
                
                var packet = new byte[result.Count];
                Array.Copy(buffer, offset, packet, 0, length);
                offset += length;

                _messageHandler.TryHandleAsync(gameSession, new ClientMessage(packet));
            }
            
            if (result.MessageType == WebSocketMessageType.Close)
            {
                await gameSession.WebSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "", CancellationToken.None);
            }
        }
    }
}