CODEWITHSUNDEEP
c#.netsocketswinsockwinsock2
ofer
ofer

Reputation: 4476

getting 10060 (Connection Timed Out) when stress testing simple tcp server

I have created simple tcp server - it works pretty well.

the problems starts when we switch to the stress tests -since our server should handle many concurrent open sockets - we have created a stress test to check this. unfortunately, looks like the server is choking and can not respond to new connection request in timely fashion when the number of the concurrent open sockets are around 100.

we already tried few types of server - and all produce the same behavior.

the server: can be something like the samples in this post(all produce the same behavior)

How to write a scalable Tcp/Ip based server

here is the code that we are using - when a client connects - the server will just hang in order to keep the socket alive.

enter code here

public class Server

{
    private static readonly TcpListener listener = new TcpListener(IPAddress.Any, 2060);

    public Server()
    {
        listener.Start();
        Console.WriteLine("Started.");

        while (true)
        {
            Console.WriteLine("Waiting for connection...");
            var client = listener.AcceptTcpClient();
            Console.WriteLine("Connected!");
            // each connection has its own thread
            new Thread(ServeData).Start(client);
        }
    }

    private static void ServeData(object clientSocket)
    {
        Console.WriteLine("Started thread " + Thread.CurrentThread.ManagedThreadId);

        var rnd = new Random();
        try
        {
            var client = (TcpClient)clientSocket;
            var stream = client.GetStream();
            byte[] arr = new byte[1024];
            stream.Read(arr, 0, 1024);
            Thread.Sleep(int.MaxValue);

        }
        catch (SocketException e)
        {
            Console.WriteLine("Socket exception in thread {0}: {1}", Thread.CurrentThread.ManagedThreadId, e);
        }
    }
}

the stress test client: is a simple tcp client, that loop and open sokets, one after the other

class Program
    {
        static List<Socket> sockets;
        static private void go(){
            Socket newsock = new Socket(AddressFamily.InterNetwork,
                                  SocketType.Stream, ProtocolType.Tcp);
            IPEndPoint iep = new IPEndPoint(IPAddress.Parse("11.11.11.11"), 2060);
            try
            {
                newsock.Connect(iep);
            }
            catch (SocketException ex)
            {
                Console.WriteLine(ex.Message );
            }
            lock (sockets)
            {
                sockets.Add(newsock);
            }

        }
        static void Main(string[] args)
        {
            sockets = new List<Socket>();
            //int start = 1;// Int32.Parse(Console.ReadLine());
            for (int i = 1; i < 1000; i++)
            {   
                go();
                Thread.Sleep(200);
            }
            Console.WriteLine("press a key");
            Console.ReadKey();




        }
    }
}

is there an easy way to explain this behavior? maybe c++ implementation if the TCP server will produce better results? maybe it is actually a client side problem?

Any comment will be welcomed !

ofer

Upvotes: 1

Views: 3372

Answers (3)

Roger Perkins
Roger Perkins

Reputation: 376

I lowered MTU from 1500 to 1300, seemed to help.

Upvotes: 0

Len Holgate
Len Holgate

Reputation: 21644

Firstly a thread per connection design is unlikely to be especially scalable, you would do better to base your design on an asynchronous server model which uses IO Completion Ports under the hood. This, however, is unlikely to be the problem in this case as you're not really stressing the server that much.

Secondly the listen backlog is a red herring here. The listen backlog is used to provide a queue for connections that are waiting to be accepted. In this example your client uses a synchronous connect call which means that the client will never have more than 1 connect attempt outstanding at any one time. If you were using asynchronous connection attempts in the client then you would be right to look at tuning the listen backlog, perhaps.

Thirdly, given that the client code doesn't show that it sends any data, you can simply issue the read calls and remove the sleep that follows it, the read calls will block. The sleep just confuses matters.

Are you running the client and the server on the same machine?

Is this ALL the code in both client and server?

You might try and eliminate the client from the problem space by using my free TCP test client which is available here: http://www.lenholgate.com/blog/2005/11/windows-tcpip-server-performance.html

Likewise, you could test your test client against one of my simple free servers, like this one: http://www.lenholgate.com/blog/2005/11/simple-echo-servers.html

I can't see anything obviously wrong with the code (apart from the overall design).

Upvotes: 0

fejesjoco
fejesjoco

Reputation: 11903

Specify a huge listener backlog: http://msdn.microsoft.com/en-us/library/5kh8wf6s.aspx

Upvotes: 0

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