i have a arduino UNO which is connected to the COM PORT 12 and an arduino Esplora which is connected to the COM PORT 20. Now I'm trying to connect the devices togehter. The Bytes from the Esplora are written to my PC. I thought there might be a way to read the Bytes with the UNO.
Do you mean that one Arduino sends stuff into the PC on Comm port 12 and you would like another Arduino to get that data from the PC through Comm port 20?
To do that you would need to write a short program on the PC that would read in the data from port 12 and send it out again on port 20.