Whenever any application in one computer sends data to another application of a different computer then it sends using IP Address and MAC Address but how does our computer know that this data is for a specific application and this data is sent by any specific application? There comes the concept of Port.
For instance, imagine your MAC Address or IP Address as the PIN code of the nearest Post Office and your house address as a Port. Whenever any parcel is sent to you it gets received by the nearest post office and then it is identified by your address where to deliver that parcel. Similarly in a computer data is first received using their IP or MAC address then it is delivered to the application whose port number is with the data packets.
Port is a logical address of a 16-bit unsigned integer that is allotted to every application on the computer that uses the internet to send or receive data.
Now every time any application sends any data, it is identified by the port that which the application sent that data and the data is to be transferred to the receiver application according to its port. We often call port as port number.
In the OSI Model ports are used in the Transport layer. In the headers of Transport layer protocols like TCP and UDP, we have a section to define port(port number). The network layer has to do nothing with ports, their protocols only care about IP Addresses.
Ports are assigned by computer i.e. operating system to different applications. Ports help computer to differentiate between incoming and outgoing traffic. Since the port is a 16-bit unsigned number it ranges from 0 to 65535.
Types of Ports
Ports are further divided into three categories:
- Well Known Port
- Registered port
- Dynamic Port
Well Known Port
- It is from the range 0 to 1023
- It is reserved for common and specifically used service
- It is used by some widely adopted protocols and services like HTTP(port 80), FTP(port 21), DNS(Port 53), SSH(port 22), etc…..
Registered Port
- It is from range 1024 to 49151
- These are used by applications or services that are not as common
- But it is used by those applications or services which require its specific port
- Organizations can ask IANA(Internet Assigned Number Authority) for any specific port number within this range
Dynamic Port
- It is from range 49152 to 65535
- It is also known as Ephemeral or Private Port
- It is used for those connections that are temporary or short-lived
- It is not registered or assigned and can be used by any process
Importance of Ports
Ports have many significance. Some of them are-
- Identification of service- Different application/services that work on the same device can be differentiated by their port numbers. For example, HTTP(Port number 80) and SMTP(port number 25) in the same computer uses different port number to ensure their data goes to the correct service
- Efficient Data Routing- When a network device receives data from different places it uses port numbers to efficiently route those data packets to the respective application
- Block traffic from specific applications/services- When we have to block incoming or outgoing traffic from a specific application/service then we need to install a firewall and specify the port number of that application/service. We block traffic from/to some specific applications/services when we find any potential threats from those applications/services
- Scalability of services- Many services can run simultaneously on the same device and can be differentiated using their port number. This helps the device to scale and support many services at the same time.
Some Popular Port Numbers
Some common/Popular port numbers that are used by those applications/services which are frequently used by us-
| Port Number | Used By |
|---|---|
| 80 | HTTP(Hyper Text Transfer Protocol) |
| 23 | Telnet |
| 25 | SMTP(Simple Mail Transfer Protocol) |
| 53 | DNS(Domain Name System) |
| 7 | Echo |
| 20/21 | FTP(File Transfer Protocol) |
| 69 | TFTP(Trivial File Transfer Protocol) |
| 443 | HTTPS(Hyper Text Transfer Protocol Secure) |
| 22 | SSH(Secure Shell) |
| 110 | POP3(Post Office Protocol version 3) |
| 67/68 | DHCP(Dynamic Host Configuration Protocol0 |
| 123 | NTP(Network Time Protocol) |
| 143 | IMAP(Internet Messaging Access Protocol) |
| 1433 | Microsoft SQL |
| 3306 | MySQL |
| 5432 | PostgreSQL |
| 27017 | MongoDB |
FAQs on Ports in Networking
Q.1: What is Port?
Answer:
Port is a logical address of a 16-bit unsigned integer that is allotted to every application on the computer that uses the internet to send or receive data. It ranges from 0 to 65535.
Q.2: What is the Socket Address?
Answer:
Socket Address is the combination of IP Address and Port Number. It is used in communication between two differnt applications/services.
Q. 3: Why Port Number is used?
Answer:
Port Number or Port is used to uniquely identify any appication/services running on the same device.