Multiping - Get MultiPing Support. Network monitoring in 60 seconds. MultiPing provides a graphical view of network performance, monitors hundreds of targets, and sends automatic alerts..
Nmap - Nmap Free Security Scanner, Port Scanner, & Network Exploration Tool. Download open source software for Linux, Windows, UNIX, FreeBSD, etc.
SmokePing - Smokeping is a tool for measuring latency.
Port Authority - A handy systems and security-focused tool, Port Authority is a very fast Android port scanner.
Fping (open source) - fping is a program to send ICMP echo probes to network hosts, similar to ping, but much better performing when pinging multiple hosts.
Fing - Discover which devices are connected to any Wi-Fi network, map devices, detect intruders, assess...