Why do you try and test two unknown pieces of code? How do you determine where the fault lies? If both pieces of code work - you're home free, but if there is a fault in either or both, it is near impossible to determine where the fault lies.

So the question is how do you prove at least one piece of code? I'd start with the transmit fisrt. If you put a MAX232 rs232 ic onto your tx pin and the output of the max232 to the serial port of your PC, you can verify the transmit code. Another method is to use a storage oscilloscope or the sound card of your PC with the appropriate software to convert it to an oscilloscope.

Once you've verified the tx code, then move onto the rx code. Have you proven your diagnostic method actually works?? That is being able to output onto P0?

Never underestimate the complexity of what you're trying to do - there can be many things apart from the code that can trip you up, so don't think having us look at the code is going to solve your problem.