For real time games, UDP gives you fine control over latency and packet retransmission -- ie, you gotta write it yourself. It''s not that hard to whip something up that gives you reliabililty and packet reordering (it''s mostly keeping a queue of incoming packets), but it is much harder to beat an existing protocol like TCP (which was designed by lots of smart people).

For turn based games, TCP gives you very simple and reliable data streams that are optimized for bandwidth. Unfortunately, the bandwidth optimizations add more places where flow control can slow down your data. With a few tweaks (like disabling Nagle''s algorithm), you can turn off some of those optimizations and improve your latency.

Finally, some games (or network game libraries) use both UDP and TCP at the same time, sending data over the right connection to get the best results.

The choice is yours, do you want to spend extra time writing your own or are you willing to suffer the moderate overhead of TCP? Maybe the best approach is to start with TCP, and then decide later whether you need to invest the time and write your own networking layer. Yes, TCP requires a socket for each connection -- but with UDP, you''ll have to dispatch and track the address of every packet you receive.

Personally, I''d recommend sticking with TCP for a truly *massive* MMORPG -- because scalability will be a big concern in everything you do.

your game might differ, it depends on how dependant you are on fast packets and your coding ability and time.

In most cases, I would use tcp.
I would rather not bother with order or lost packets (UDP), especially since this is a home project and a cleaned up tcp packet can be plenty fast for 56k modems.

TCP is perfect for many occasions and proves still much faster than a layer of DirectPlay.

I''ve only heard of UDP being used for "twitch" games such as quake and tribes where online multiplayers were expected to be in the tens with 56k modems.

To TCP or UDP..

Actually, in my own projects I use both. The more frequent and ''real-time'' data is sent UDP. Initial login & registration, and anything not time-critical is done with a TCP connection.

Mainly, I use UDP to relay player locations and events.

I haven''t tried writing an RPG; I have mainly stuck to, more or less, arcade style systems. You can put one together relatively easily, although there are a lot of details to fill/code in. No one piece is really difficult, but getting it all working together can be tricky.

I''m also a firm believer in designing small and building up. I suggest a similar approach. Build and test pieces and spend the time to design the entire game architecture before you start any real coding.

// CHRIS

When I say "TCP is optimized for bandwidth", I mean it was designed for things like FTP and mail protocols -- which exchange lots of data over a variety of network connections. It recognizes when the link can handle more data on the fly, then sends larger packets/more data before pausing for an acknowledgement.

Saai, the fact that Anon''s post was exactly 1 sentence long with a broad generalization about an extreme position pretty much eliminates his comment from consideration.

The other posts have presented a pretty good overview of the trade-offs of both protocols. Use the one that seems to work best for your game.


DavidRM
Samu Games