Port number is one of the most commonly discussed topics in a computer network. We always use to by heart the port number of POP3, SMTP, DHCP, DNS, etc and prepare for the interview. But have you ever searched for what is the port number, why do we need a port number, and what is the use of it. Hello friends, I am your host Abhishek Gupta and in this post, I am going to explain to you the basics of the port number in networking.
What is Port Number?
The Port number is a unique ID of a protocol in a computer network. Every protocol in a computer network has a unique ID, now the question is why do we need this port number, and what is the use of it.
Let’s take an example, in a network there are 10 computers connected together and out of 10 computers one is a DHCP server, and the remaining nine are DHCP hosts who all are getting IP Addresses from the DHCP server. How your computer network understands which one is a server and which one is the host.
It can be identified only from the port number. as we know that the DHCP protocol has two port numbers 67 (for server) and 68 (for the host). The PC assigned with the port number 67 is the server and all the other PC are assigned with the port number 68 is the host. This is how your computer network will understand which one is the DHCP server or host.
Let’s take another example, you might have noticed in the most popular mailing app outlook, we have to configure incoming mail server (POP) and Outgoing mail (SMTP) and have to assign the port number. Hence the POP port number 110 is without SSL (Encryption) on the other hand 995 is with SSL (Encryption). If you assign the port number 110, your outlook will understand this user is not using an encryption connection and if you assign 995, outlook will understand the user is using an encryption connection.
So, guys, this is the basic concept of the port number in computer networking. Hope you all enjoyed reading this.
Here is a small video, I have explained about what is port number in networking.
List of most commonly used port number in networking:
| Protocols | Port No |
| FTP | 21 |
| TELNET | 23 |
| HTTP | 80 |
| DNS | 53 |
| SSH (Secure Shell) | 22 |
| SMTP | 25 |
| DHCP Server | 67 |
| DHCP client | 68 |
| POP3 (Post Office Protocol, version 3) | 110 |
| NTP (Network Time Protocol) | 123 |
| IMAP (Internet Message Access Protocol) | 143 |
| SNMP (Simple Network Management Protocol) | 161 |
| IMAP3 (Internet Message Access Protocol 3) | 220 |
| SSL (Secure Socket Layer) | 443 |
| NetBIOS (Network Bios) | 139 |
| RIP (Routing Information Protocol) | 520 |
Here is a post on computer network topology. Hope, you will enjoy reading this:
What is Computer Network Topology | Network Topology Types with Diagram and Advantages
