Hello, the specs are clear (a rare thing for a change ;), it seem to be a re-implementation of the old SerialMirror utility, so without further ado I can implement the program in MS VisualStudio Community Edition and deliver you the project and the compiled binaries.
Some clarification discussion may be needed for inter-character spacing if any (it the other side is a micro controller and there is no handshake it may not be able to process data fast enough). also the baud rate parameter will include the other line parameters (character size, parity, stop bits) or they are fixed and only the baud rate changes, minor stuff.
So yeah, not much left to be said, bid with confidence, Zevedei is with you.
Cheers,
Zeve