The Importance of Addressing TCP/IP Software Ports for Security Installations

Marco Cardazzi

On August 27th In IP Solutions, IP Surveillance Video, IP Tech Tips, Networking


Along with IP and MAC addresses, devices communicating with each other over LANs and the Internet use channels of communication which are called the TCP/IP software ports. These are not physical plug-in ports on a switch or router; instead they are internal channels which are set up by two network devices when they start a communication session.

You can think of the TCP/IP software ports as being similar to the channels in a cable television connection. With cable TV there is a single coax cable coming into a home, yet that single cable can provide hundreds of channels to view. With a single Internet connection you can have multiple communications going on simultaneously. While you sit at your PC and have the Fox News and CNN websites open, your daughter is watching a YouTube video and your wife is downloading a book onto her Kindle, all at the same time.

There are 65,535 TCP/IP software ports, and this is how they work. When you input into the address line of Internet Explorer the “http://” portion indicates that you want to be connected to port 80 on the ADI web server. When the ADI server is reached, it will negotiate with your PC to establish specific ports to be used for the back and forth transmission of data. For this particular session your PC will communicate to the ADI server on port 80; the ADI server will transmit its information back to your PC on a different port number, such as 41,212. This port arrangement will remain active during this specific communication session. If you also open another website simultaneously, the same process occurs. You type in, which will be directed to port 80 on the CNN server. That server will then set up a return path port number that will be different from the one that is being currently used by the ADI web site.

Here’s a screen shot from the Wireshark IP packet analyzer which shows the software ports in use on a PC at IP address is communicating with the Yahoo website at the Internet IP address of

wireshark software ports 11313

This image contains all of the source (Src) and destination (Dst) addressing information including the Ethernet II (or MAC) addresses, the IP addresses, and the source and destination software ports.

Proper setting of the software ports is critical for electronic security technicians when installing devices such as IP cameras where the intention is that the client/user will be able to remotely access the device from over the Internet. The software ports must be properly configured in the IP device itself, in the router’s “port forwarding” screen, and also in the firewall of the DSL or cable modem.

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