Long Distance Chat Server?

Hi,

I am currently working on a networking course and we've been asked to create a simple chat server between 2 machines in C (both client and server on the same local machine is enough). I was able to do this using both TCP and UDP, including features like having multiple clients and multicasting.

I do have a few follow up questions:

1. How should I go about it if I want to make this chat server with one machine in USA and other in London? What additional steps do I need to take?

2. What kind of tradeoffs should I consider when deciding protocols?

Thanks!