Ping
From Hackepedia
ping is a tool written by the late Mike Muus to measure latency and round-trip time between two hosts connected by an Internet, often it is also used to simply debug if the other host is up. It works by sending an ICMP type 8 packet to the remote host which replies with an ICMP type 0 packet. Sometimes there is firewalls preventing a ping from receiving a reply.
This would look like so:
$ ping -c 1 www.yashy.com PING mail.yashy.com (206.248.137.44): 56 data bytes --- mail.yashy.com ping statistics --- 1 packets transmitted, 0 packets received, 100.0% packet loss
A similar tool to ping would be traceroute.
