Install: go get github.com/grahamking/latency
Run: sudo latency [hostname].
Example output:
$ sudo ./latency github.com
Measuring round-trip latency from 192.168.1.26 to 192.30.252.131 on port 80
Latency: 116.601914ms
The sudo is needed to open a raw socket. If you know how to do this with capabilities, please do tell.
latency can also run in auto mode, where it tests a range of well known sites (which will be geo-balanced), and some servers in specific locations. It's fun, try it! sudo latency -a
latency sends a TCP SYN packet (the opening of the three-way handshake) to a remote host on port 80. That host will respond with either a RST (if the port is closed), or a SYN/ACK (if the port is open). Either way, we time how long it takes between sending the SYN and receiving the response. That's your network latency.
There are of course many other ways to measure this (mtr is nice), but this is a fun exercise in using raw sockets and binary encoding in Go.
License: GPL.