Hi Anneke,
I'm certainly no expert on this matter but my gut feeling would be that you need to delve into adapter development? I would suppose so because if you are situated on layer 3 or layer 4 you would need to have some "itelligence" that encapsules the meaning of all the bits that you are transferring (with HTTP or RFC being on layer 7 for example).
Please let me know if I missunderstood your requirements.
Cheers
Jens
