ping

nmap "ping"

I usually use nmap instead of ping to check the state of a given host and port. nmap is essential for diagnosing network problems, but using the defeault port-scan mode can be problematic because a lot of servers have automated Intrusion Detection System tools. These will trigger if they see that you are scanning a range of ports. Typically this will cause the system to block your IP address thus adding to your network diagnosis problems. The trick is to tell nmap to use a stealth scan and to just check a single remote port. This is usually good enough to not tigger an IDS. The following will stealthily check the state of port 22 (SSH) without sending a PING.

nmap -P0 -sS -p22 www.example.com

This is a similar check for port 80 (http):

nmap -P0 -sS -p80 www.example.com