how to clear a port in linux

C++
netstat -tulnap        // list all ports and processes
netstat -anp|grep "port_number"     // show port details
sudo fuser -k Port_Number/tcp       // free the port needed
# or
lsof -n -i :'port-number' | grep LISTEN  // get port details
# sample  response:  java   4744 (PID)  test  364u  IP0 asdasdasda   0t0  TCP *:port-number (LISTEN)
kill -9 PID  // free portkill -9 $(lsof -t -i:8080)
Source

Also in C++: