The ping program, which is named after the sound made by a sonar echo, checks the availability of a computer on a network. The program is included with all standard operating systems. If, however, there is a firewall between your computer and the host which filters out ping packets, your computer may incorrectly be shown as unavailable. Our online tool therefore also offers the option of checking a different host from h-online.com.
To do so, it sends echo response packets to the host using ICMP. It calculates the round-trip time using the time difference between this and the echo reply. Ping is specified in RFC 1574.