/etc/services
From FreeBSDwiki
The services file contains information regarding the known services available in the Internet. For each service a single line should be present with the following information:
official service name port number / protocol name aliases
For example, say you want to know what port and protocol mdns might use:
dave@abulafia % cat /etc/services | grep dns dnsix 90/tcp #DNSIX Securit Attribute Token Map dnsix 90/udp #DNSIX Securit Attribute Token Map sdnskmp 558/tcp sdnskmp 558/udp mdns 5353/tcp #Multicast DNS mdns 5353/udp #Multicast DNS
