EDI (electronic data interchange) over ISDN

I have to make a project that implements EDI ( Electronic Data Interchange), and I have to communicate over ISDN ( probably X.25 protocol). The project must obey the OFTP ( ODETTE FTP ) standard, and that is the reason why I have to use ISDN.

The part about creating EDI files I managed to understand so this is not a problem, but the part regarding transmission using ISDN is a bit fuzzy. I guess the hardware part would be something like this: PC->Router->ISDN device->Telephone line . Furthermore I will have to implement the communication protocol ( X.25 ) and I can hardly find real code examples of this protocol. So in order to speed up the things a little bit, anyone who worked with EDI / ISDN and is kind to give me some advices will be more than welcome.

Thank you, 

M. Razvan