Computer Ports

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Computer Ports

All computer devices on a network need a channel to allow them to communicate with each other.

First you need a plug or physical connection. But the ports we are talking about here are 'virtual' or software assigned ports.

The language of software ports is defined by TCP/IP. TCP/IP stands for Transmission Control Protocol/Internet Protocol and is the communications protocol used by UNIX systems and now the Internet.

Under this protocol, every PC needs a unique address. This is the Machine Address Code or MAC. This serial number is hard-wired into the network card.

There is also the IP address which is like a telephone number for computer devices. But that address could be carrying a number of services.

To stop the lines getting crossed, various ports can be opened on an IP address.

So the ones you might encounter are

	Port 80 is used by the web
	Port 110 is assigned to email otherwise known as POP 3
	Port 143 is used by IMAP part of email
	Port 25 is for SMPT which is a part of the email system
	Port 21 is taken over for FTP services
	Port 22 is for SSH
	Port 23 is Telnet
	Some applications have adopted ports for example PC Anywhere uses 5631 and Remote Desktop port 3389

There are over 65,000 possible ports, many of which have been assigned for specific uses. Others have been usurped by players of particular games or pieces of equipment.

If you fancy yourself as a computer 'brain surgeon' feel free to re-assign your ports. But don't be surprised if everything goes very quiet if you do.

You can check your ports and IP address if you visit http://www.canyouseeme.org/

ping is a tool used to test if host can be reached on the IP network. Ping sends “echo request” packets to the target. By timing the interval and response rate, ping estimates the round-trip time and reliability between the hosts.

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