Ping is an extremely useful utility for troubleshooting network connectivity. However, on today’s networks, pings are often discarded. And with the prevalence of firewalls and load balancers it is often necessary to test the availability and response time of a particular port anyway. The hping utility allows us to do exactly this, and more.

Hping is a packet crafting utility. It is extremely flexible and here we will only touch the surface of what it can do.

In this example we will ping a webserver on tcp port 80 (-p 80) by sending it a SYN (-S) packet.

$ hping -S -p 80 google.com
HPING google.com (eth0 66.249.92.104): S set, 40 headers + 0 data bytes
len=44 ip=66.249.92.104 ttl=47 id=10442 sport=80 flags=SA seq=0 win=5720 rtt=97.7 ms
len=44 ip=66.249.92.104 ttl=47 id=40838 sport=80 flags=SA seq=1 win=5720 rtt=97.7 ms
len=44 ip=66.249.92.104 ttl=47 id=64607 sport=80 flags=SA seq=2 win=5720 rtt=97.7 ms
len=44 ip=66.249.92.104 ttl=47 id=10443 sport=80 flags=SA seq=3 win=5720 rtt=97.7 ms
^C
--- google.com hping statistic ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 97.7/97.7/97.7 ms

Look familiar? The output is formatted very similarly to ping. In fact hping can perform traditional icmp echo pings as well by using the “-1″ switch.

This utility has been immensely helpful in troubleshooting and documenting performance problems and testing the capabilities of firewalls. It’s also very useful for detecting when sshd comes back up after a system reboot (hint: -p 22).