Question

I wrote a TCP server to use the BeginAccept/EndAccept pattern. With this, I coded up a simple UnitTest using a TcpClient, and measured each portion. All tests are localhost, so I am surprised to see that TCP connection is consistently taking 1 second. I have set the Socket.NoDelay = true although I believe this only affects Send/Receive. I am not receiving the first packet of data. Any help or ideas on speed this up are appreciated.

Note: I can not change the client side to keep the connection open, and I need to be able to handle a lot of requests per second if possible.

Server Side:

public void Start()
{
    System.Net.IPHostEntry localhost = System.Net.Dns.GetHostEntry(System.Net.Dns.GetHostName());
    System.Net.IPEndPoint endpoint;
    int port = Properties.Settings.Default.ListenPort;

    //
    // Setup the connection to listen on the first IP, and specified port
    //
    endpoint = new IPEndPoint(IPAddress.Any, port);
    listenSocket = new Socket(endpoint.Address.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
    listenSocket.Bind(endpoint);
    listenSocket.NoDelay = true; // do not wait 200 milliseconds for new data to be buffered on the connection
    listenSocket.Listen(int.MaxValue);
    Console.WriteLine("Listening on {0}:{1}", localhost.AddressList[0], port);

    //
    // Post the accept. The accept method will continuously post a new accept as soon as a connection is made
    //
    while (true)
    {
        accepted.Reset();
        Connection connection = connections.Pop();
        listenSocket.BeginAccept(AcceptCallback, connection);
        accepted.WaitOne();
    }
}

private static void AcceptCallback(IAsyncResult ar)
{
    accepted.Set();

    Connection connection = ar.AsyncState as Connection;
    Socket remoteSocket = null;

    try
    {
        remoteSocket = listenSocket.EndAccept(ar);
        remoteSocket.NoDelay = true;                
        connection.RemoteSocket = remoteSocket;

        //
        // Start the Receive cycle
        //
        Receive(connection);             
    }
    catch (SocketException)
    {
        Disconnect(connection);
    }           
}

Simple Test Client:

[TestMethod()]
public void ClientTest()
{
    TestContext.BeginTimer("Connection");
    TcpClient client = new TcpClient("localhost", 10300);
    NetworkStream stream = client.GetStream();
    TestContext.EndTimer("Connection");
    ...

Using a LoadTest I loaded 25 users, and the Transaction “Connection” always takes above 1 second.

Answer 1

Not sure why, but simply changing this:

TestContext.BeginTimer("Connection");          
TcpClient client = new TcpClient("localhost", 10300);            
TestContext.EndTimer("Connection");

To this:

TestContext.BeginTimer("Connection");
TcpClient client = new TcpClient();
client.Connect("localhost", 10300);       
TestContext.EndTimer("Connection");

Drops the time from 1 second to .13 seconds. Will have to investigate as to why, but hopefully this will help somebody out in the future.