Talkswitch 24-CA User Manual page 191

TalkSwitch has the technology that helps keep this information up to date
so that the system can function properly after an IP address change has
been detected and updated.
What is a port number?
In an IP address like 64.26.209.103:5060, the port number is 5060, the
number after the colon.
Port numbers are required so that a computer or device can support multiple
applications or streams of simultaneous data communication. Each stream or
application uses a unique port number. You can think of it like mailing a
letter to a friend in an apartment building at a specific address. You need to
specify the apartment number as well as the address of the building, so that
the mail can reach the correct final destination.
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