client/server

I'm in the process of seperating client/server. Having said that, to my understanding, the first thing to do is create a master server in whatever language - this will maintain the list of available game servers and return the list to the client upon request. My intention is to code the master server in c# as that is where my knowledge is...
... now ... can someone please explain what object do i have to pass to the client? what data structure is the client expecting the list to be in?

P.S. So basically the role of a master server is just this right? maintains list of game servers, bans, filtering.


Your help is much appreciated!!