Port may be defined as a communication end point in computer networking and at the software level within an operating system, it referrs to a logical construct that identifies a specific process to send and receive message, data or information. Thus said, each specific process to exchange information is identified with a specific port number that may range from 0 to 65535. There are millions of computers all over the world in data centers. They all are able to exchange information to and from—-using network port and IP address. IP used to reach a particular destination, i.e., a server, computer or a device via network. Port is used to identify an application service through which data transmission proceeds forth and goes back. The combination of port and IP forms a socket that’s a must when a connection established between two computers.
In our daily life we use smart phones. When you communicate with other, your phone uses a number that gets connected to whom you target. Here, network used only to provide connectivity and a set of numbers used to convey speech or messages through it to the target. In this occurrence, the set of mobile numbers is a perfect example of port number that we use very often in our practical life.
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Category of Port Numbers
Port numbers may range from 0 to 65535. Each port number has a specific function and classified into three categories based on availability and service functionality. The categories are discussed below.
Port ‘0’ to ‘1023’ : These run on TCP/UDP. These are well-known port numbers assigned to specific servers by the IANA.
Port ‘1024’ to ‘49151’ : The numbers within this range are registered by organisation to avail specific service. Application developers can register such kind of numbers with IAMA. These are also called registered or semi-reserved ports. Many software developers use these numbers.
Port ‘49152’ to ‘65535’ : These are high range ports that anyone can use. No need of registration. Generally, client programs, such as web browsers can use these numbers. While visiting a website, your browser can use any number from within this range during that session. These are also known as ephimeral or public port .
The bulk of the ports use TCP to exchange information while the rest uses UDP. In terms of security the former is more significant than the latter. If you don’t need much security, then you can run the latter, otherwise the former is best. The numbers from’0′ to’ 49151′ are assigned to the registrant consumers by the IANA. RFC1700 contains the list of port numbers.
Important Port Numbers Used for Specific Protocol
| Port | Protocol | Name | Description |
| 18 | TCP/UDP | msp | Sends text message. |
| 20 | TCP/UDP | FTP | FTP data transfer. |
| 21 | TCP/UDP | FTP | FTP connection. |
| 22 | TCP/UDP | SSH | Secure Shell Service. |
| 23 | TCP | Telnet | Telnet Service. |
| 25 | TCP | SMTP | Simple Mail Transfer Protocol. |
| 42 | TCP/UDP | Name Server | Name Service. |
| 43 | TCP | Nicname | Whois directory service. |
| 50 | TCP/UDP | Remote Mail Checking. | |
| 53 | TCP/UDP | Domain | DNS Name Resolver. |
| 67 | UDP | Bootps | Bootstrap Protocol Service. |
| 80 | TCP | HTTP | Hyper Text Transfer Protocol. |
| 110 | TCP | POP3 | Post Office Protocol v3 for e-mail communication. |
| 113 | UDP | Auth | Authentication Service. |
| 115 | TCP | SFTP | Simple File Transfer Protocol. |
| 443 | TCP | HTTPS | Hyper Text Transfer Protocol Secure. |
How Does Port Work?
Most of the internet protocol uses either TCP or UDP, whichever is needed based on circumstances. While exchanging information or data between two or through multiple devices via internet, the sending device dispatches data packet combined with IP address including within it both the network and the host. In the internet there may be various IP services such as SSH, FTP, SMTP, HTTP, HTTPS etc. While you are going to connect your client with a server, you have to specify the service you want to connect to so that data is sent to an appropriate application, otherwise, it will not be connected to through the desired channel of communication. Suppose you are going to transfer files from your pc to a remote server. Here you need a remote connection to the targeted server. So, in order to be connected to the web server, the client ought to use FTP that you can identify by using the port number 21 in default.
What Is Port Scanning?
Port scanning is a kind of application process of determining whether a port is accessible or not. Generally, application software can check which numbers assigned with value are open in a network. Ports are like open doors—-through which incoming traffic can enter a computer system. It allows information to be passed in and out. When a scanner runs on a system or a device to check whether a port is open or not, it can also detect the presence of security equipment like setting up of firewall between the sender and the receiver. This system of scanning is of utmost importance from security perspective. Thus with port scanner you can check port’s current status, firewall configuration as well as security strength of the system. This is also called fingerprinting. The hackers misuse this technique to access to break into a computer system to ransack it to their personal ends. That’s why, while scanning a port, the target host must be compliant with RFC793.
What Can I know from Port Scanner?
Port scanner can inform you about your computer system’s security configuration like firewall setup, its accessibility and other vulnerabilty if found in the way to access a port via network.
- You can see firewall strength.
- Port’s current status to incoming traffic.
- With scanner you can enable or disable service detection.
- Enable or disable operating system detection.
- Enable or disable host disconnection.
- Periodic scan will help you monitor possible attack by intruders that you can prevent.
- After scanning a port, you can get it in one of the three condition, such as open, closed or blocked.
- In case of open port, the server may be reached, connection can be done as the port listens on the connection. Using this tactic hackers break into a computer systems, steal away files, sensitive information and even inject malware. It is always at risk unless antivirus or firewall is not configured properly by the administrator of the host.
- Sometimes, access to the entry point, assigned with a specific number may be closed or denied. In this case, the host gives a reply indicating that connection will not be given to the port. Here the admin should take up proper steps like setting up a firewall against attacks by the hackers.
- In case of filtered, dropped or blocked port, while someone trying to access a host, it doesn’t give any reply to the port. Here the system is least vulnerable to attacks by cybercriminal.
List of Port Scanner
There are many port scanner service that you can use to check your system’s network port for security concern. You can use anyone of the scanner mentioned as follows:
Port Scanner for Android
There are many port scanner available in playstore for android. All of these are free. You have to just download and install in order to use to check up port’s current status as to whether it is accessible or not. These are mentioned as follows:
