Iphone

1st - Client sends secure data to server to be processed.
2nd - Server takes that secure data and processes it.
3rd - The data processed on the server is sent back to the client securely.

Using C#.NET or VB.NET what is the most efficient networking object to use to achieve a professional level of client/server network programming? TCP? UDP or something?

What is world of warcraft using for example or everquest 2? Please provide information about this issue.

My first step is to create a client that communicates securely & efficiently with the server.

Iphone

Well, Blizzard used to use the same network stuff until it was reverse engineered, GPL'd and released as Bnetd (remember battle.net?). Well, that was shut down and now WoW uses a completely new network library. Not many details on it as it's in-house. Here's some info on that: Battle.net - Wikipedia, the free encyclopedia

Everquest actually uses a P2P-based architecture for their network protocol. There's a good article on engineering EverQuest on IEEE Spectrum: IEEE Spectrum: Engineering Everquest. There's a not at the bottom on an article that talks about them using P2P protocols as their network backbone.

Here's some more information on what different games use (everquest is not in this list). I don't know how useful it is to you, but I thought it was interesting: http://l7-filter.sourceforge.net/protocols

If you don't want to reinvent the wheel, I'd go with blackspark's suggestions for libraries. However, if you want to pull a Blizzard and make something new and unique, go for it.

Here is a good list of popular network APIs that are currently out there: http://irrforge.org/index.php/Network_APIs