Connection log entries - random port number recorded

Hello,

I have postgres set to log all connections.  I run it on port 5432.  I
have noticed in the postgres logs that the port being used to connect to
the database is logged but never equal to 5432.  The ip address recorded
is correct but the port number recorded is always a different number
each time.

This is 7.4.1-3 on cygwin.  Has anyone noticed this on other platforms?

Mike