Might as well keep your question here, you started it here.
Firstly, you need a converter from RS232 signal levels to TTL levels. Generally, look like:
and are available from Amazon, or a local hobby shop if you have one, in many flavors.
Then you need to define in more detail what it is you want your Arduino to do with the "connection to the server" in order to receive guidance about what Arduino would be appropriate. There's so much you could do, depending, so any advice at this point is worth what you pay for it - that is to say, at this point, worth nothing, until you give us hints.