How to lookup port usage and release the port. (Resolve Issue: Port in-use by unknown process)

When we develop web applications, a very common problem is that sometimes we don't know what is using the current port that we need. And we cann't start our server while getting this kind of exception:

First we could look at the Task Manager to see whether we can get the process which is using this port. But what if we got nothing? Kill every suspects? It's dangerous and sometimes doesn't help at all.
Restart the computer? Ohh that'll work, that's also what I did previously but it's so out!!! It's so painful to restart everything and it's really unneccessary.

Now I get one solution, which is very easy and helpful.

For example, I want to user port "8080" but it's in use by unknown process.

First open the cmd, execute => netstat -aon|findstr "8080"
Then you'll get result like this:
  TCP    0.0.0.0:8080           0.0.0.0:0              LISTENING       87460
  TCP    [::]:8080                 [::]:0                    LISTENING       87460

Now we know who is using the port, the process with PID "87460".

Then in the cmd, we execute => taskkill /pid 87460 -f
Then you'll get result like this:
SUCCESS: The process with PID 87460 has been terminated.

That's it! Then you retart the server, everything will be fine.