Ok... Since you haven't specified, I'll assume you want to connect with what you have as opposed to buying some (quite possibly) tricky hardware to find... But there are still a lot of questions...
You don't say if you intend to have this server/client pair connected to the internet, and you don't say if you have any speed requirements.
If you are wanting to connect with the best speed you can, you'll want to get 100 base T/1000 base T ethernet cards, matching 1000 base T ethernet cables (talk to a local computer specialist for recommended brands, as some are better than others, and some even vary depending on local conditions). If you intend the network to be connected, you'll want a 1000 base T router (since there are only going to be a couple of computers on your network)...
Now you may be wondering why I keep saying 1000 base T components... Well, you have to take into consideration that your network is only as fast as the slowest component on the network connections. So even if your ethernet cards are 1000 base T, if your cable is 10/100 base T(Cat5) then your network will only go at 100 base T speeds. If your cables are 1000 base T, but your router is 100 base T compatible only, then the network (so long as it's routed through the router, instead of having multiple NICs in one computer) can only work up to 100 base T speeds, got it?
Having covered all that, I guess the most direct answer to your question is that depending on what equipment you have or want to buy, you'll either want Cat5 (100 base T) or Cat5c (1000 base T).
Best of luck, and I hope you work it out...
You don't say if you intend to have this server/client pair connected to the internet, and you don't say if you have any speed requirements.
If you are wanting to connect with the best speed you can, you'll want to get 100 base T/1000 base T ethernet cards, matching 1000 base T ethernet cables (talk to a local computer specialist for recommended brands, as some are better than others, and some even vary depending on local conditions). If you intend the network to be connected, you'll want a 1000 base T router (since there are only going to be a couple of computers on your network)...
Now you may be wondering why I keep saying 1000 base T components... Well, you have to take into consideration that your network is only as fast as the slowest component on the network connections. So even if your ethernet cards are 1000 base T, if your cable is 10/100 base T(Cat5) then your network will only go at 100 base T speeds. If your cables are 1000 base T, but your router is 100 base T compatible only, then the network (so long as it's routed through the router, instead of having multiple NICs in one computer) can only work up to 100 base T speeds, got it?
Having covered all that, I guess the most direct answer to your question is that depending on what equipment you have or want to buy, you'll either want Cat5 (100 base T) or Cat5c (1000 base T).
Best of luck, and I hope you work it out...