Now if I do DebugSerial.print("123") and connect to monitor the port I do not see anything. How thise sketch is supposed to work? If I do Serial.print() I do see the output. Inside the code example everywhere DebugSerial.printnl() is used. How I supposed to see the result?
You connect two UNO using your DebugSerial(8, 9) Port. Upload sketches onto UNO-1 (Transmitter) and UNO-2 (Receiver). Open SM for UNO-2 and observe 123.