TcpListener

    public class AsyncService
    {
        private static Logger logger = LogManager.GetCurrentClassLogger();
        private IPAddress listenerAddress;
        private int listenerPort;
        private Func<string, string> respond;

        public AsyncService(IPAddress address, int port, Func<string, string> func)
        {
            listenerAddress = address;
            listenerPort = port;
            respond = func;
        }

        public async void Run()
        {
            TcpListener listener = new TcpListener(listenerAddress, listenerPort);
            listener.Server.ReceiveTimeout = 5000;
            listener.Server.ReceiveBufferSize = 65536;
            listener.Start();
            logger.Info(String.Format("Сервер запущен на {0}:{1}", listenerAddress, listenerPort));
            while (true)
            {
                try
                {
                    TcpClient tcpClient = await listener.AcceptTcpClientAsync();
                    Task t = Process(tcpClient);
                    await t;
                }
                catch (Exception ex)
                {
                    logger.Error(ex);
                }
            }
        }

        private async Task Process(TcpClient tcpClient)
        {
            string clientEndPoint = tcpClient.Client.RemoteEndPoint.ToString();
            logger.Info("Подключение с адреса " + clientEndPoint);
            try
            {
                string request;
                byte[] data = new byte[tcpClient.ReceiveBufferSize];
                using (NetworkStream stream = tcpClient.GetStream())
                {
                    using (MemoryStream ms = new MemoryStream())
                    {
                        int numBytesRead;
                        while ((numBytesRead = await stream.ReadAsync(data, 0, data.Length)) > 0)
                        {
                            ms.Write(data, 0, numBytesRead);
                        }
                        request = Encoding.UTF8.GetString(ms.ToArray(), 0, (int)ms.Length);
                    }

                    string response = respond.Invoke(request);
                    logger.Info("Отправка ответа");
                    logger.Info(response + "\r\n");
                    data = Encoding.UTF8.GetBytes(response);
                    await stream.WriteAsync(data, 0, data.Length);
                }
            }
            catch (Exception ex)
            {
                logger.Error(ex);
            }
            finally
            {
                if (tcpClient.Connected)
                    tcpClient.Close();
            }
        }
    }