Discussion on the advantages of TCP vs UDP (and vice versa) has a history which is almost as long as the eternal Linux-vs-Windows debate. As I have long been a supporter of the point of view that both UDP and TCP have their own niches (see, for example, [NoBugs15 [ithare.com]]), here are my two cents on this subject [ithare.com].
Note for those who already know the basics of IP and TCP: please skip to the ‘Closing the Gap: Improving TCP Interactivity’ section, as you still may be able to find a thing or two of interest.
It's a primer, or a refresher, or a skip. We have all kinds here. Enjoy, or don't.