Find the Process and PID using the Specific port in Ubuntu
Ubuntu is a Linux Operating System so you need to have Root privilege to get the process information.
netstat command is used to show the ports and processes in Linux.
netstat -nlp command is used to show the processes using network.
Now filter the process that using a specific port.
netstat -nlp|grep 3000
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
tcp 0 0 0.0.0.0:3000 0.0.0.0:* LISTEN 16698/node
Here 16698 is the PID and node is the process.