strange port communication

Hi,
I have two computer communicating (one inside the network, the other on the outside the network).

The are both using strange port numbers that are not commonly used.  (Port 52497 for the external IP address and 9678 internally)

My question is
1. Shouldn't the firewall  be configured to prevent outgoing ports except for typical ports (80, 443, etc?)
2. Should the firewall be configured to only allow in commonly used ports (port 80, 443)?

Thanks.