ieee488:
I would just receive 1 byte send 1 byte.
That probably won't work. The second byte would be missed while he is forwarding the first byte.
Use Serial for one of the devices (pins 0 & 1). You have to be very selective about debug prints, because everything you print will go to one of the devices. Also, you have to disconnect pin 0 to upload new sketches over the USB port.
Then use AltSoftSerial for the other device (pins 8 & 9). AltSoftSerial and Serial will not interfere with each other.
SoftwareSerial is very iinefficient, because it disables interrupts for long periods of time. It cannot send and receive at the same time, so printing on SoftwareSerial prevents receiving anything. SoftwareSerial interferes with everything.