Multiplayer is probably one of the hardest features to learn in DBC/DBP. I personally have wanted to establish a working text RPG and found it very difficult.
Some tips you might want to think about when trying to figure out how to work multiplayer gaming:
1. Generally, one of the computers will have to act as a server for the larger multiplayer games. It MIGHT be possible to do up to 4-player games with no central server, but it's going to take a lot of bandwidth.
2. Depending on the game you're programming, you will probably have to send data from the client to the server on every command the client issues that other clients need to be aware of. The server will then send the data to all of the other clients after verifying it. In a no-server MP model, a client sends data to the other client, and that client sends data to the original client. Of course, this is only with 2 players. With 4 players and no central server you have each of those 4 clients passing data to each other. Not pretty.
3. Not all of the clients need to know everything right away. Don't always send Hit Points unless they need to be known. Instead, send the death when the player dies, and the health when you click on the character (if that would show their hit points). You probably wouldn't even need to know HP when a player healed another player, just tell the server you're healing with spell "x", server determines amount of healing and then sends data to the client saying "you've been healed for "x" by "y spell" cast by "z". The server would also probably want to keep a record of all vital data of a player, else hacking would become easy. This would also cause problems, however, with bandwidth.
All in all, it's in no way easy. These are just my views on the subject; they could be completely wrong. It's just how I think it should be done.
