The TFTP server is listening on all adapters. If you run (netstat -an | find "69") at a command prompt you should see the following.
UDP 0.0.0.0:69 *:*
The 0.0.0.0:69 means that UDP port 69 is open on all adapters.
Boom2ns - By default, the TFTP server binds to the address "any", meaning all addresses. You can specify one address to bind to int he configuration dialog.
Right mouse click the TFTP icon on the system tray and select Open to get to the status window, then select File -> Configure to get to the configuration dialog. There should be a drop down of available addresses from which you can select the address to bind to.