Sockets - Check That If Another Computer In The Network Send Some String Data To The Listener Computer?

i have a task to create a TCP Server (a program that is listening on its network card interfaces for incoming data stream).I have search on the internet and i found that i can use two methods : Socket or TCPListener class.I have created an example for Socket class, but i wondering how could i test it? I need to check that if another computer in the network send some string data to the listener computer , then this message should be displayed.Here is the example from microsoft that i am using for TCP Server using Socket:

Public Shared Sub Main()
' Data buffer for incoming data.
Dim data = nothingc[code]....

But it does not work because of the PORT setting.If in the TCP Server i have "Dim localEndPoint As New IPEndPoint(ipAddress, 0)" the client crashes, but if i change the port from any (0) to 11000 for example,the client works fine.Do you know why?

Later edit2:Maybe i should have started with this question:Which method is recommended for my scope?asynchronous or synchronous method ?