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How-To: Change which port numbers are associated to port values.

In some cases (not many, but some) you may wish to change the port numbers associated to various port names.

For example, SMTP is associated with port 25, POP3 with 110, NNTP with 119, and so-on.

Changing these values as outlined below can have wide ranging effects on applications running on the machine and could cause problems that appear unexplainable during many support calls - be careful here.

Under Windows NT, there is a SERVICES file located in the %SystemRoot%\System32\Drivers\Etc directory which contains these associations.  IPSentry makes use of these settings when converting a port (service) name to number (such as SMTP to 25). 

Let's say for instance that all of your relay servers are accessible only on port 9999 rather than 25.  You would simply change the reference to SMTP in the services file to 9999 .

Related Topics

• IPSentry - How To - Index

• ICANN - Internet Corporation for Assigned Names & Numbers

• The RFC Editor