WebSocketServer.cs

using System;
using System.Net;
using System.Net.WebSockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace WebTest
{
    class Program
    {
        static void Main(string[] args)
        {
            var listener = new HttpListener();
            listener.Prefixes.Add("http://localhost:8080/");
            listener.Start();

            Task.Run(async () =>
            {
                while (true)
                {
                    var ctx = await listener.GetContextAsync();

                    if (ctx.Request.IsWebSocketRequest)
                        Task.Factory.StartNew(() => WebSocketHandle(ctx));
                }
            }).Wait();
        }

        public async static void WebSocketHandle(HttpListenerContext context)
        {
            WebSocketContext webSocketContext = null;
            try
            {
                webSocketContext = await context.AcceptWebSocketAsync(subProtocol: null);
                var ipAddress = context.Request.UserHostAddress.ToString();
                Console.WriteLine($"Connected: {ipAddress}");
            }
            catch (Exception e)
            {
                context.Response.StatusCode = 500;
                context.Response.Close();
                Console.WriteLine($"Exception: {e}");
                return;
            }
            WebSocket webSocket = webSocketContext.WebSocket;
            try
            {
                byte[] receiveBuffer = new byte[1024];
                while(webSocket.State==WebSocketState.Open)
                {
                    var receiveResult = await webSocket.ReceiveAsync(new ArraySegment<byte>(receiveBuffer), CancellationToken.None);
                    if (receiveResult.MessageType == WebSocketMessageType.Close)
                        await webSocket.CloseAsync(WebSocketCloseStatus.NormalClosure, "", CancellationToken.None);
                    else
                        await webSocket.SendAsync(new ArraySegment<byte>(receiveBuffer, 0, receiveResult.Count), WebSocketMessageType.Text, receiveResult.EndOfMessage, CancellationToken.None);
                }
            }
            catch(Exception e)
            {
                Console.WriteLine($"Exception: {e}");
            }
            finally
            {
                if (webSocket != null)
                    webSocket.Dispose();
                Console.WriteLine($"Disconnected");
            }
        }
    }
}