How to make sure that a certain Port is not occupied by any other process

You can use "netstat" to check whether a port is available or not.

Use the netstat -anp | find "port number" command to find whether a port is occupied by an another process or not. If it is occupied by an another process, it will show the process id of that process.

You have to put : before port number to get the actual output

Ex netstat -anp | find ":8080"

netstat -ano|find ":port_no" will give you the list.
a: Displays all connections and listening ports.
n: Displays addresses and port numbers in numerical form.
o: Displays the owning process ID associated with each connection .

example : netstat -ano | find ":1900" This gives you the result like this.

UDP    107.109.121.196:1900   *:*                                    1324  
UDP    127.0.0.1:1900         *:*                                    1324  
UDP    [::1]:1900             *:*                                    1324  
UDP    [fe80::8db8:d9cc:12a8:2262%13]:1900  *:*                      1324

It's netstat -ano|findstr port no

Result would show process id in last column