Sonar is a network reconnaissance utility which runs all its scans from plugins. The currently supported plugins are an ICMP scan and an ACK scan which can see if hosts that don’t respond to ICMP are online.
You can download it from the following link: https://packetstormsecurity.com/files/download/29516/sonar-1.0BETA4.tar.gz
Source: https://packetstormsecurity.com/files/29516/sonar-1.0BETA4.tar.gz.html