如何使用.Net套接字重用TCP端点地址

Question

I have some client-server socket code that I want to be able to construct and (re)connect to periodically the same endpoint address: localhost:17999

Here is the server:

// Listen for a connection:
IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Loopback, 17999);             
Socket listener = new Socket(IPAddress.Loopback.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
listener.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
listener.Bind(localEndPoint);
listener.Listen(1);

// Accept the connection and send a message:
Socket handler = listener.Accept();
byte[] bytes = new byte[1024];
bytes = Encoding.ASCII.GetBytes("The Message...");                 
handler.Send(bytes);

// Clean up
handler.Shutdown(SocketShutdown.Both);
handler.Close();
handler.Dispose();

listener.Shutdown(SocketShutdown.Both);
listener.Close();
listener.Dispose();

And here is the client:

byte[] bytes = new byte[1024];
Socket receiver = new Socket(IPAddress.Loopback.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
receiver.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
receiver.Connect(new IPEndPoint(IPAddress.Loopback, 17999));

int num_bytes_received = receiver.Receive(bytes);
string result = Encoding.ASCII.GetString(bytes, 0, num_bytes_received);

receiver.Shutdown(SocketShutdown.Both);
receiver.Close();
receiver.Dispose();

When I create the client and server for the first time, it works fine. However when I create it again, I get an error:

"A request to send or receive data was disallowed because the socket is not conne cted and (when sending on a datagram socket using a sendto call) no address was supplied"

I would like to be able to spin up this mechanism arbitrarily whenever I need to with the following order of events:

1. Launch the server and wait to accept a connection
2. Launch the client and connect to the server
3. Accept the client connection at the server
4. Send a message to the client
5. Repeat when necessary

How can I do this?

Thx in Advance!

EDIT: Each time I build the client and server objects it is from a different process.

Answer 1

You have two issues:

1) You're closing the listener. Just leave it open.

2) You're setting ReuseAddress on the wrong socket and way too late. Set it on the listening socket before you call bind (since that's when you use the address).

Setting ReuseAddress on a socket you aren't going to bind doesn't do anything. You can remove that from the client.

Answer 2

I tried what Gene suggested and it seems to work:

// Listen for a connection:     
IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Loopback, 17999);
using (Socket listener = new Socket(IPAddress.Loopback.AddressFamily, SocketType.Stream, ProtocolType.Tcp))
{

    listener.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
    listener.Bind(localEndPoint);
    listener.Listen(1);

    Thread t = new Thread(() =>
    {
        // Accept the connection and send a message:
        using (Socket handler = listener.Accept())
        {
            byte[] bytes = new byte[1024];
            bytes = Encoding.ASCII.GetBytes("The Message...");
            handler.Send(bytes);
        }
    });
    t.Start();
    t.Join();
}

Thanks, all!