Nmap is a very useful network tool. It is an open source security/port scanner, released under GPL.
The project is very active (last release was 4 days ago at time of writing).
Zenmap is the GUI interface to Nmap.
The only major issue is that much like wireshark, Nmap requires the winpcap driver.
I see quite a few threads requesting Nmap/Zenmap (https://portableapps.com/search/node/nmap), yet we've still not got an official release.
I'd like to see one...