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.
CurrPorts - CurrPorts displays the list of all currently opened TCP/IP and UDP ports on your local computer.
TCPView - TCPView is a Windows program that will show you detailed listings of all TCP and UDP endpoints on...
Ping Meter Gadget - Customizable, graphical, semi-transparent ping (latency) meter.
TcpView For Linux - TcpView For Linux. Touch screen friendly design graphical network connections viewer for Linux.
KeyCDN Tools - Website speed test, online curl, ping tool, https/2 and other services