What is it?
From their own page:
GGPO is a networking library that game developers can use to add
networked gameplay support to arcade style games.
GGPO's latency hiding techniques give each player a gameplay experience
that is nearly indistinguishable from playing with
their friends locally, even against players around the world.
tl;dr - You can play emulated games like Jojo's bizarre adventure over the internet via GGPO - with excellent performance.
Getting and Setting up GGPO
1) Go to http://ggpo.net/download and follow all the instructions.
3) Move the Jojo's ROM to GGPO's roms folder. (For legal reasons we will not link to any such thing)
4) Setup your GGPO account, join the Jojo channel, and have some fun!
Known Bugs, etc
- NEW accounts on GGPO are not always usable instantly. It is believed (unproven) by Fayk that certain things such as passowrd changes are effectively not updated until the server reboots/crashes (this happens often enough, booting everyone off the chat lobby).
- You cannot reliably record your own games via the 'input recording' menu option due to known emulator bugs and lack of support. Have someone else spectate and record or spectate your own game and record. Fraps/external recording works fine of course.
- If one or both players does NOT have the savestate, the game will appear to work but be de-synced. This will be most noticeable by them picking the default char (1P=Jotaro, 2P=Dio) 99% of the time, playing oddly, and typically not continuing when you defeat them, since they probably saw themselves as victorious against you on their end.
- GGPO can have difficulty connecting with your opponent - this is normal. If you don't see the game fully start working within 20 seconds (allowing for a slow load of roms on a slow computer) then close the window and try again. Often people will 'double' challenge, sending more than one challenge at a time. Typically you should accept all these at once and hope that one of them connect. Once the game starts, further issues (de-syncs or crashes) are rare.
- The combo counter is not visible for 2P due to an unrelated FBA bug.