Question

What does the ​ netstat command do? The netstat command has many options. Please
explain the following commonly used options and briefly explain the meaning of the output. How
can you know which program (i.e., process) is using a specific port?

~$​ netstat -a
~$ ​ netstat -l
~$ ​ netstat -s
~$ ​ netstat -p
~$ ​ netstat -r
~$ ​ netstat -ie

You can ignore those lines related to UNIX domain sockets.

Answer 1

Solution:

Netstat command:

As name stated, netstat is formed from the two words network and statistics. Basically, it is a command-line network utility that's controlled via commands. Netstat commands deliver basic statistics on all network activities and informs users which ports are open for tasks and on which addresses and ports the corresponding connections (TCP, UDP) are running.

In single line, we can say that "To show detailed network status information the netstat command are used.".

Explanation of given options:

~$​ netstat -a : This command results in listing all the LISTENING Ports of TCP and UDP connections.
~$ ​ netstat -l : This command results in listing all active listening ports connections.
~$ ​ netstat -s : This command results in displaying statistics for each protocol like TCP, UDP, ICMP, and IP protocols. To specify a set of protocols the -s parameter in the command can be used.
~$ ​ netstat -p : This command results in showing the statistics for the specified protocol.
~$ ​ netstat -r : ​​​​​​​This command results in displaying Kernel IP routing table with netstat and route command.
~$ ​ netstat -ie :​​​​​​​ This command results in showing Kernel interface table, it is similar to ifconfig command.

How can you know which program (i.e., process) is using a specific port?

We can use the netstat command with the -np flags and a pipe to the find or findstr commands.

Syntax:

netstat -np <protocol> | find "port #"

For example: netstat -np TCP | find "80"

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