Bits of .NET

🔌 WebSockets in .NET Core

Real-time is essential. WebSockets in .NET Core enable bidirectional communication.

📝 WebSocket Setup

// Program.cs
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.UseWebSockets();

app.Map("/ws", async context =>
{
    if (context.WebSockets.IsWebSocketRequest)
    {
        using var webSocket = await context.WebSockets.AcceptWebSocketAsync();
        await HandleWebSocket(webSocket);
    }
    else
    {
        context.Response.StatusCode = 400;
    }
});

async Task HandleWebSocket(WebSocket webSocket)
{
    var buffer = new byte[1024 * 4];
    var result = await webSocket.ReceiveAsync(buffer, CancellationToken.None);
    
    while (!result.CloseStatus.HasValue)
    {
        var message = Encoding.UTF8.GetString(buffer, 0, result.Count);
        Console.WriteLine($"Received: {message}");
        
        var response = $"Echo: {message}";
        var responseBytes = Encoding.UTF8.GetBytes(response);
        await webSocket.SendAsync(
            responseBytes,
            result.MessageType,
            result.EndOfMessage,
            CancellationToken.None);
        
        result = await webSocket.ReceiveAsync(buffer, CancellationToken.None);
    }
    
    await webSocket.CloseAsync(
        result.CloseStatus.Value,
        result.CloseStatusDescription,
        CancellationToken.None);
}

app.Run();

🎯 Advanced WebSockets

// WebSocket middleware
app.Use(async (context, next) =>
{
    if (context.Request.Path == "/ws")
    {
        if (context.WebSockets.IsWebSocketRequest)
        {
            using var webSocket = await context.WebSockets.AcceptWebSocketAsync();
            await HandleWebSocket(webSocket);
        }
        else
        {
            context.Response.StatusCode = 400;
        }
    }
    else
    {
        await next();
    }
});

// WebSocket manager
public class WebSocketManager
{
    private static readonly List _sockets = new();
    
    public static async Task Add(WebSocket socket)
    {
        _sockets.Add(socket);
    }
    
    public static async Task Broadcast(string message)
    {
        var bytes = Encoding.UTF8.GetBytes(message);
        foreach (var socket in _sockets)
        {
            if (socket.State == WebSocketState.Open)
            {
                await socket.SendAsync(
                    bytes,
                    WebSocketMessageType.Text,
                    true,
                    CancellationToken.None);
            }
        }
    }
}

// JavaScript client
const socket = new WebSocket('ws://localhost:5000/ws');

socket.onopen = function() {
    console.log('Connected');
    socket.send('Hello from client');
};

socket.onmessage = function(event) {
    console.log('Server:', event.data);
};

💡 WebSocket Tips

• Use for real-time communication
• Handle connection lifecycle
• Broadcast to multiple clients
• Handle errors gracefully
• Consider SignalR for complex scenarios