Pidgin file transfer over bonjour protocol

Question

i'm running pidgin (the latest in opensuse 13.2 repo available), in yast firewall i've enabled bonjour/avahi service and opened the 5298 port. Now the chat works flawlessly. But i can't transfer files to another pc in the same lan. So on both the machines i've stopped the firewall, and the transfer starts to work! Which ports are used? Through the use of netstat, i've discovered that the port used to transfer changes randomly on every transfer! is it possible to define a range of opened ports? Thank you in advance for any reply.