Net Send Messaging

I have windows xp service pack 2 and we ahve another machine with windows xp service pack2. i have sp2 firewall enabled on the system. when i send message, it does not work. when i diable firewall then the windows message from net send command works fine. The messanger service and alerter service both are enabled "Automatic".

Can anyone tell me which ports i need to open so that users can send me messages from net send command and i which port i need to open so that i can maintain the security instead of diabling the firewall.

It's very urgeng, Please help me...



Thanks & Regards
Hari