Is there a WebSocket client implemented for .NET?

Here's a quick first pass at porting that Java code to C#. Doesn't support SSL mode and has only been very lightly tested, but it's a start.

using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;

public class WebSocket
{
    private Uri mUrl;
    private TcpClient mClient;
    private NetworkStream mStream;
    private bool mHandshakeComplete;
    private Dictionary<string, string> mHeaders;
    
    public WebSocket(Uri url)
    {
        mUrl = url;
        
        string protocol = mUrl.Scheme;
        if (!protocol.Equals("ws") && !protocol.Equals("wss"))
            throw new ArgumentException("Unsupported protocol: " + protocol);
    }
    
    public void SetHeaders(Dictionary<string, string> headers)
    {
        mHeaders = headers;
    }
    
    public void Connect()
    {
        string host = mUrl.DnsSafeHost;
        string path = mUrl.PathAndQuery;
        string origin = "http://" + host;

        mClient = CreateSocket(mUrl);
        mStream = mClient.GetStream();

        int port = ((IPEndPoint)mClient.Client.RemoteEndPoint).Port;
        if (port != 80)
            host = host + ":" + port;

        StringBuilder extraHeaders = new StringBuilder();
        if (mHeaders != null)
        {
            foreach (KeyValuePair<string, string> header in mHeaders)
                extraHeaders.Append(header.Key + ": " + header.Value + "\r\n");
        }

        string request = "GET " + path + " HTTP/1.1\r\n" +
                         "Upgrade: WebSocket\r\n" +
                         "Connection: Upgrade\r\n" +
                         "Host: " + host + "\r\n" +
                         "Origin: " + origin + "\r\n" +
                         extraHeaders.ToString() + "\r\n";
        byte[] sendBuffer = Encoding.UTF8.GetBytes(request);

        mStream.Write(sendBuffer, 0, sendBuffer.Length);

        StreamReader reader = new StreamReader(mStream);
        {
            string header = reader.ReadLine();
            if (!header.Equals("HTTP/1.1 101 Web Socket Protocol Handshake"))
                throw new IOException("Invalid handshake response");

            header = reader.ReadLine();
            if (!header.Equals("Upgrade: WebSocket"))
                throw new IOException("Invalid handshake response");

            header = reader.ReadLine();
            if (!header.Equals("Connection: Upgrade"))
                throw new IOException("Invalid handshake response");
        }

        mHandshakeComplete = true;
    }
    
    public void Send(string str)
    {
        if (!mHandshakeComplete)
            throw new InvalidOperationException("Handshake not complete");

        byte[] sendBuffer = Encoding.UTF8.GetBytes(str);

        mStream.WriteByte(0x00);
        mStream.Write(sendBuffer, 0, sendBuffer.Length);
        mStream.WriteByte(0xff);
        mStream.Flush();
    }

    public string Recv()
    {
        if (!mHandshakeComplete)
            throw new InvalidOperationException("Handshake not complete");

        StringBuilder recvBuffer = new StringBuilder();

        BinaryReader reader = new BinaryReader(mStream);
        byte b = reader.ReadByte();
        if ((b & 0x80) == 0x80)
        {
            // Skip data frame
            int len = 0;
            do
            {
                b = (byte)(reader.ReadByte() & 0x7f);
                len += b * 128;
            } while ((b & 0x80) != 0x80);

            for (int i = 0; i < len; i++)
                reader.ReadByte();
        }
        
        while (true)
        {
            b = reader.ReadByte();
            if (b == 0xff)
                break;

            recvBuffer.Append(b);           
        }

        return recvBuffer.ToString();
    }
    
    public void Close()
    {
        mStream.Dispose();
        mClient.Close();
        mStream = null;
        mClient = null;
    }

    private static TcpClient CreateSocket(Uri url)
    {
        string scheme = url.Scheme;
        string host = url.DnsSafeHost;

        int port = url.Port;
        if (port <= 0)
        {
            if (scheme.Equals("wss"))
                port = 443;
            else if (scheme.Equals("ws"))
                port = 80;
            else
                throw new ArgumentException("Unsupported scheme");
        }

        if (scheme.Equals("wss"))
            throw new NotImplementedException("SSL support not implemented yet");
        else
            return new TcpClient(host, port);
    }
}

Now, SuperWebSocket also includes a WebSocket client implementation SuperWebSocket Project Homepage

Other .NET client implementations include:

• Microsoft WebSocket client prototype
• WebSocket-Sharp
• Anaida