System.Net.Sockets.Socket.EndAccept C# (CSharp) Method

        internal Socket EndAccept(out byte[] buffer, out int bytesTransferred, IAsyncResult asyncResult)
        {
            if (NetEventSource.IsEnabled) NetEventSource.Enter(this, asyncResult);
            if (CleanedUp)
            {
                throw new ObjectDisposedException(this.GetType().FullName);
            }

            // Validate input parameters.
            if (asyncResult == null)
            {
                throw new ArgumentNullException(nameof(asyncResult));
            }
            AcceptOverlappedAsyncResult castedAsyncResult = asyncResult as AcceptOverlappedAsyncResult;
            if (castedAsyncResult == null || castedAsyncResult.AsyncObject != this)
            {
                throw new ArgumentException(SR.net_io_invalidasyncresult, nameof(asyncResult));
            }
            if (castedAsyncResult.EndCalled)
            {
                throw new InvalidOperationException(SR.Format(SR.net_io_invalidendcall, "EndAccept"));
            }

            Socket socket = (Socket)castedAsyncResult.InternalWaitForCompletion();
            bytesTransferred = (int)castedAsyncResult.BytesTransferred;
            buffer = castedAsyncResult.Buffer;

            castedAsyncResult.EndCalled = true;

            if (s_perfCountersEnabled)
            {
                if (bytesTransferred > 0)
                {
                    SocketPerfCounter.Instance.Increment(SocketPerfCounterName.SocketBytesReceived, bytesTransferred);
                }
            }

            // Throw an appropriate SocketException if the native call failed asynchronously.
            if ((SocketError)castedAsyncResult.ErrorCode != SocketError.Success)
            {
                // Update the internal state of this socket according to the error before throwing.
                SocketException socketException = new SocketException(castedAsyncResult.ErrorCode);
                UpdateStatusAfterSocketError(socketException);
                if (NetEventSource.IsEnabled) NetEventSource.Error(this, socketException);
                throw socketException;
            }

#if TRACE_VERBOSE
            if (NetEventSource.IsEnabled)
            {
                try
                {
                    if (NetEventSource.IsEnabled) NetEventSource.Info(this, $"SRC:{LocalEndPoint} acceptedSocket:{socket} acceptedSocket.SRC:{socket.LocalEndPoint} acceptSocket.DST:{socket.RemoteEndPoint} bytesTransferred:{bytesTransferred}");
                }
                catch (ObjectDisposedException) { }
            }
#endif
            if (NetEventSource.IsEnabled)
            {
                NetEventSource.Accepted(socket, socket.RemoteEndPoint, socket.LocalEndPoint);
                NetEventSource.Exit(this, socket);
            }
            return socket;
        }

        void OnNewClient(IAsyncResult _asyncResult)
        {
            System.Net.Sockets.Socket ClientSocket = ListenSocket.EndAccept(_asyncResult);
            ListenSocket.BeginAccept(OnNewClient, null);

            SetKeepAlive(ClientSocket, 1000 * 60, 1000);

            var NewClient = new TelnetClient {
                Socket = ClientSocket
            };

            if (Clients.ClientConnected(NewClient) == ClientAcceptanceStatus.Rejected)
            {
                NewClient.WasRejected = true;
                ClientSocket.Close();
            }
            else
            {
                // We will handle all the echoing echoing echoing
                //var echoCommand = new byte[]
                //{
                //    (byte)TelnetControlCodes.IAC,
                //    (byte)TelnetControlCodes.Will, // TODO: Handle client response denying this request
                //    (byte)TelnetControlCodes.Echo,
                //    (byte)TelnetControlCodes.IAC,
                //    (byte)TelnetControlCodes.Dont,
                //    (byte)TelnetControlCodes.Echo,
                //};
                //ClientSocket.Send(echoCommand);

                ClientSocket.BeginReceive(NewClient.Storage, 0, 1024, System.Net.Sockets.SocketFlags.Partial, OnData, NewClient);
                Console.WriteLine("New telnet client: " + ClientSocket.RemoteEndPoint.ToString());
            }
        }