Netcid is blocked by Avast

I am using the work/medium setting for firewall. I have callstation which is an answering machine software and on a call with caller id, the id is sent to other computers on my network with a program called netcid. The netcid uses port 42685 to send the information. When I set the avast firewall on the lowest setting the netcid works, but on the setting work/medium, it blocks the information. I need to know how to configure avast to let the information thru on port 42685.
Thanks