Roberto, you're looking to run multiple protocols over the same serial port.

What you need is a "master" protocol that manages some kind of sub-protocols. When the master protocol on the PC receives a serial packet it must decode it and realize what data is contained in it and route it to the right application.

Actually, PPP (Point-To-Point Protocol), often used to connect to Internet, does just that. It allows TCP/IP, UDP, and (unfortunately) NetBIOS, etc. to all be transmitted over a single serial line. It "wraps" the TCP/IP, UDP, etc. protocols into packets that are then transported using the PPP protocol. When the packet arrives, the receiving system decodes the PPP packet and obtains the TCP/IP, UDP, etc. packets that were sent.

If the protols you are using between the MCU and the applications are all recognized by PPP perhaps you can implement PPP. If not, I think you'll have to custom-write it youself.

Craig Steiner