How to find the numbers NOT currently listed in /etc/services?

Current employment only lists currently used Ports in /e开发者_如何学JAVAtc/services. So it's hard to tell where others left off. How can I find, what Port numbers are not listed there?

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Do you mean ports of programs actually running on your computer? You may be able to use netstat or lsof to find these.

Or are you simply looking for common ports that your particular /etc/services may be missing? Wikipedia has a list at http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers if you wish to augment yours.