Socket declaration just doesn't work

Socket Listener = new Socket(0, SocketType.Stream, ProtocolType.Tcp);

This is practially straight out of a tutorial example and I can't find anything wrong with it, but Visual Studio keeps underlining it in red signalling errors (4 or 5 of them too). By having "Socket Listener;" in the class and then having "Listener = new Socket(...);" inside the method where it's used I get rid of the red lines, but then when I declare the second socket in the same way, they just come back.

I'm not so sure about the parameters (expecially that first 0), but there are also errors showing up about the fact that I'm declaring something as type Socket (I did notice that while listing the name spaces I would be using, System.Net and System.Net.Sockets did not show up as options in the drop down menu like I thought they would've).

use this

Code:

---


        TcpListener listener;
       
          // Step 1: create TcpListener

 //listener = new TcpListener(System.Net.IPAddress.Parse("0"),4000);
            listener = new TcpListener(4000);
                       

            // Step 2: TcpListener waits for connection request
            listener.Start();

---

where 4000 is a port, if doesn't work change the port

The The TcpListener class is designed for synchronous data transfer, and my application requires asynchronous communication.

And for some reason the problem has now seemed to disappear. I don't remember specifically making any changes to the way I did it, but the source file was fairly small at the time, so I just created a new clean file and coded from the beginning.