How to check if port is in use on Linux or Unix

To check if a port is in use on Linux or Unix, you can use the netstat command.

For example, to check if port 80 is in use, you can use the following command:

netstat -tulpn | grep :80

This will display a list of all network connections that are using port 80.

Alternatively, you can use the lsof command to check if a port is in use.

For example:

lsof -i :80

This will display a list of all processes that are using port 80.

You can also use the ss command to check if a port is in use.

For example:

ss -lntu | grep :80

This will display a list of all network connections that are using port 80.

Keep in mind that these commands may not be available on all Linux or Unix systems. In such cases, you can use the telnet command to check if a port is open.

For example:

telnet localhost 80

If the port is open, this command will establish a connection to the port and you will see a blank screen. If the port is closed or not in use, you will see an error message.

Note: You will need to have permission to access the port in order to check if it is in use. If you do not have permission, you may need to ask the system administrator to check the port for you.