Whenever you need to check the availability of TCP port numbers (and check, which process uses each of them), it is convenient to use this utility. Windows OS standard tool would be to use DOS command-line 'netstat -ao' (displays port number and 'Process ID'). To see the actual process using that port, you can also use 'Task Manager' (switch on the display of 'Process ID' column). It is not convenient to use these programs separately in real time; therefore they are combined in this utility.