If you encounter the error message "This port is already in use", it means that the specified port is currently being used by another process. To resolve this issue, you can follow the steps below:

Step 1: Install net-tools

sudo apt install net-tools

Step 2: Get the list of ports and associated processes

netstat -tulpen

Step 3: Kill the process using the specified port

kill -9 PID

Replace "PID" with the process ID (PID) of the process using the port you want to free up.

By following these steps, you will be able to identify the processes using specific ports and terminate them if necessary, allowing you to free up the port for other applications or services.