Solution of Port6How many tcp ports are open in the port range 1-1000 on all hackingarena.com servers?
The following command will list all open TCP ports between port 1 and 1000. Nmap -sT -p1-1000 hackingarena.no --open. Since we need only the number we can use grep too.
Scanning the other hosts the sum of the open ports is 97 (this is the status of February 2020).