Hi Russel,
I don't know SOAP... i will try google to find informations!

I already written the specifications of the commands.
They are all ASCII printable characters terminated with CR. The first 2 chars are the command ID to identify the command, and after this there are the optional parameters separated by ",".
Example :

AA,<param1>,<param2>,....,<paramN> CR

The response has to be first 2 chars the same of the received command, 2 chars status, and then optional data (for example the record data)
Example :

AA,00, <optional data> CR

The main problem is not the protocol itself but the "philosophy" (hope i write it correctly)of the protocol and how to implement it on the PC side, and this is the problem of my collegue and this caused a "hot" discussion.

I know is a bad idea to request code but can you suggest me links where find examples in Delphi for implementing a state machine?
In this way i can help my collegue and calming down discussions.

Thank you for your suggestions!

Massimo.