establish a connection between server and client

There are several levels of networking you can use.
Here is what you can consider:

Low sockets level using System.Net.Sockets.Socket, a little higher socket levels using System.Net.Sockets.UdpClient (UDP), System.Net.Sockets.TcpListener/System.Net.Sockets.TcpClient (TCP), .NET remoting, WCF (self-hosted or not).

Lower levels will need Marshaling and/or Serialization; you may also need to know how to create and use DataContract and/or ServiceContract, especially with WCF. One of the most essential aspects will be threading and thread synchronization.

I would suggest you don't try to communicate between applications (it depends on your goal though). It's usually more productive to think in terms of service (not necessarily client-server) and clients.

Making even most elementary examples on every level would make a really big article, may be… hard to estimate… some tens of pages. Who will write it for you? Better try to find articles of separate topic in CodeProject and create prototype applications using each technique. Only in this way you will be able to feel them well enough to decide on designs on your applications.

Basic advice: don't try to send UI controls and the like, like some do. Create pure-data types and send pure data; create loose coupling between data and UI, isolate UI from data model, universal functionality and application-specific functionality.

—SA

Google is your friend: Be nice and visit him often. He can answer questions a lot more quickly than posting them here...

This is not a new problem: A quick google using your subject line as the search term gave nearly 400 million hits, most of which explain how to do it. Google[^]

You need to pick up a book or look at some online sampls and start reading.

yes OriginalGriff is right. you should search it on the google first. you will get billion result for that, and also you will get the answer from the google...
But it depend on how you search it on google[^]