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What is a port number?
In an IP address like 64.26.209.103:5060, the port number is the number after the colon ‘:’. For this example, 5060 is the specified port.
Port numbers are required so that a computer or device can support multiple appli- cations 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 friend in an apartment building at a specific address. You need to specify the apartment number as well as the building address, so that the mail can reach the proper final destina- tion.
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TalkSwitch User Manual