TCP/IP Port

What is it?

Port numbers are digits written after IP address separated by a colon.
TCP port is a 16-bit unsigned value.
There is finite no. of ports available 65,535.
Used for successful data packet transfer.
A socket, in which we connect to another system running some software takes place with a combination of an IP address and port number.
For instance, FTP application has 20 & 21 listening port.
Therefore, FTP server application when it starts will bind itself to TCP ports 20 and 21, and wait for connections in order to send and receive data.

A single host can host multiple instances in the same service by using a different port number.

Socket

ftp://192.168.0.137: 21

IP Address

.

17

18

19

22

23

14 .

65535

For FTP, default port no. = 21

We can change the listening port.

Port no.

The port number identifies what type of port it is.
For example, port 80 is used for HTTP traffic.
Some ports have numbers that are assigned to them by the IANA.

http://google.com

Google Web Server

Listening port 80

You type google.com
You get the page.
Google web server is an HTTP server specifically listening to an incoming port number 80.

TCP/IP Port

So, we can set up no. of a web server that has one listening port on the default port 80.
And another website on the same server, same IP address but with listening on a different port (expect 80).
There are total 65535 TCP and UDP port numbers available.

Well-Known Ports.

Public Ports.

Port 0 to 1023 are Well-Known Ports.

eg. http, ftp, smtp,pop, imap, dhcp etc.

A host will bind a listen port number with an application, it will then use this port to listen for and accept connections from remote computers.
Note that once an application binds itself to a particular port, that port can not be used by any other application.
Most major applications have a specific port that they listen on and they register this information with an organization called IANA.
This table has some Well-Known Ports (port no. 0 to 1023) of TCP specifies the port used by the server process as its contact port.

Where & How to Use

Practically we use this port numbers in different fields such as:

Server application configurations like Oracle, Sharepoint, SQL Server, etc. requires to set up port number.
We use port number for troubleshooting purposes specifically, troubleshoot malware and identify a rogue process.

We can check which ports are being used by our PC with the command line.
Open Command Prompt > type netstat -a > Enter.

Displays current TCP/IP network connections and statistics with the port number.

Port

numbers

Download TCPView software, a Microsoft software will give graphical interface of connection status.
Here you can see all running application with a local address and remote address with their respective port used.
Those applications which are using UDP protocol to connect, they don't have a remote address and port number, because UDP is a connectionless protocol.
Here we can see the total no. of packets received and sent.
This software has many features which allow us to close the connection, WHOIS lookup and so on.

TCP/IP Port

What is it?

Port numbers are digits written after IP address separated by a colon.

TCP port is a 16-bit unsigned value.

There is finite no. of ports available 65,535.

Used for successful data packet transfer.

A socket, in which we connect to another system running some software takes place with a combination of an IP address and port number.

For instance, FTP application has 20 & 21 listening port.

Therefore, FTP server application when it starts will bind itself to TCP ports 20 and 21, and wait for connections in order to send and receive data.

A single host can host multiple instances in the same service by using a different port number.

Socket

ftp://192.168.0.137: 21

IP Address

.

17

18

19

​

​

22

23

14

.

.

65535

For FTP, default port no. = 21

We can change the listening port.

Port no.

The port number identifies what type of port it is.

For example, port 80 is used for HTTP traffic.

Some ports have numbers that are assigned to them by the IANA.

http://google.com

Google Web Server

Listening port 80

You type google.com

You get the page.

Google web server is an HTTP server specifically listening to an incoming port number 80.

TCP/IP Port

So, we can set up no. of a web server that has one listening port on the default port 80.

And another website on the same server, same IP address but with listening on a different port (expect 80).

There are total 65535 TCP and UDP port numbers available.

Well-Known Ports.

Port 0 to 1023 are Well-Known Ports.

eg. http, ftp, smtp,pop, imap, dhcp etc.

A host will bind a listen port number with an application, it will then use this port to listen for and accept connections from remote computers.

Note that once an application binds itself to a particular port, that port can not be used by any other application.

Most major applications have a specific port that they listen on and they register this information with an organization called IANA.

This table has some Well-Known Ports (port no. 0 to 1023) of TCP specifies the port used by the server process as its contact port.

Where & How to Use

Practically we use this port numbers in different fields such as:

Server application configurations like Oracle, Sharepoint, SQL Server, etc. requires to set up port number.

We use port number for troubleshooting purposes specifically, troubleshoot malware and identify a rogue process.

We can check which ports are being used by our PC with the command line.

Open Command Prompt > type netstat -a > Enter.

Displays current TCP/IP network connections and statistics with the port number.

​​​

Port

numbers

Download TCPView software, a Microsoft software will give graphical interface of connection status.

Here you can see all running application with a local address and remote address with their respective port used.

Those applications which are using UDP protocol to connect, they don't have a remote address and port number, because UDP is a connectionless protocol.

Here we can see the total no. of packets received and sent.

This software has many features which allow us to close the connection, WHOIS lookup and so on.

Port Number