ASTM / HL7 communication via Ethernet shield

i have device claims communicate via tcp/ip in either client or server mode.
it should communicate using astm or hl7 communication protocol.

i have simple question.
is there easy way set arduino ethernet shield  act server, , responds <enq> requests <ack>?
i want the arduino listen on specific port, , when receives byte(05) - or <enq>,  want respond byte(06) or <ack> - , monitor communication in between...

not sure if has library or site explains how this? or if possible??
and need network hub or switch accomplish task or can connect device directly ethernet shield using cat5 cable??

any insight appreciated.

thanks
scott

ok - lack of response bit discouraging... perhaps should try bite size pieces:

forget hl7 part of question... let's start one.
1.  can establish cat5 cable connection computer directly using ethernet shield or need hub?

so have   

computer's ethernet port---- cat5 cable -------ethernetshield
                                                                                          |||||||||||||||||||||||
                                                                                               arduino ----------usbcable-----------laptop

Arduino Forum > Using Arduino > Networking, Protocols, and Devices (Moderator: fabioc84) > ASTM / HL7 communication via Ethernet shield

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