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

        public IAsyncResult BeginConnect(string host, int port, AsyncCallback requestCallback, object state)
        {
            if (NetEventSource.IsEnabled) NetEventSource.Enter(this, host);
            if (CleanedUp)
            {
                throw new ObjectDisposedException(this.GetType().FullName);
            }

            if (host == null)
            {
                throw new ArgumentNullException(nameof(host));
            }
            if (!TcpValidationHelpers.ValidatePortNumber(port))
            {
                throw new ArgumentOutOfRangeException(nameof(port));
            }
            if (_addressFamily != AddressFamily.InterNetwork && _addressFamily != AddressFamily.InterNetworkV6)
            {
                throw new NotSupportedException(SR.net_invalidversion);
            }

            if (_isListening)
            {
                throw new InvalidOperationException(SR.net_sockets_mustnotlisten);
            }

            IPAddress parsedAddress;
            if (IPAddress.TryParse(host, out parsedAddress))
            {
                IAsyncResult r = BeginConnect(parsedAddress, port, requestCallback, state);
                if (NetEventSource.IsEnabled) NetEventSource.Exit(this, r);
                return r;
            }

            ThrowIfNotSupportsMultipleConnectAttempts();

            // Here, want to flow the context.  No need to lock.
            MultipleAddressConnectAsyncResult result = new MultipleAddressConnectAsyncResult(null, port, this, state, requestCallback);
            result.StartPostingAsyncOp(false);

            IAsyncResult dnsResult = DnsAPMExtensions.BeginGetHostAddresses(host, new AsyncCallback(DnsCallback), result);
            if (dnsResult.CompletedSynchronously)
            {
                if (DoDnsCallback(dnsResult, result))
                {
                    result.InvokeCallback();
                }
            }

            // Done posting.
            result.FinishPostingAsyncOp(ref Caches.ConnectClosureCache);

            if (NetEventSource.IsEnabled) NetEventSource.Exit(this, result);
            return result;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            System.Diagnostics.Stopwatch watch = new System.Diagnostics.Stopwatch();
            var ControllerIPAddress = new IPAddress(new byte[] { 192, 168, 0, 2 });
            var ControllerPort = 40001;
            var ControllerEndPoint = new IPEndPoint(ControllerIPAddress, ControllerPort);
            _client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

            var header = "@";
            var command = "00C";
            var checksum = "E3";
            var end = "\r\n";
            var data = header + command + checksum + end;
            byte[] bytes = new byte[1024];

            //Start Connect
            _connectDone.Reset();
            watch.Start();
            _client.BeginConnect(ControllerIPAddress, ControllerPort, new AsyncCallback(ConnectCallback), _client);
            //wait 2s
            _connectDone.WaitOne(2000, false);

            var text = (_client.Connected) ? "ok" : "ng";
            richTextBox1.AppendText(text + "\r\n");
            watch.Stop();
            richTextBox1.AppendText("Consumer time: " + watch.ElapsedMilliseconds + "\r\n");
        }