All your OSC devices and software have an IP address, it might look like this: 192.168,2,12
Your device is listening on a port (say 8000) and sending on another (say 9000). So if you want to reach the above device, you need to connect to
192.168.2.12:8000. When that device is sending out messages, it will send it to the port 9000 of the other device. So that device needs to receive on 9000 and send on 8000.
Parameters are selected by their address. If you want to move a slider on the above device, you could send
192.168.2.12:8000/slider x (where x is the value you want to set the slider to).
You can say that slider is the message and x is the value. Values can be floats, integers, strings, blobs, midi notes and probably some other things I don't know about. Obviously, you can't send any value types to any address (well you can, but don't expect anything good).
I'd be happy to answer more specific questions, or if you need to be walked through a certain setup.
(I'll take this opportunity to plug my own little OSC apps for iOS:
Sylvain
