Available

  
            License: Freeware $0.00
            OS: Java,Linux,Mac OS X,Unix,Win2000,Win7 x32,Win7 x64,WinServer,WinVista,WinVista x
            Requirements: Requires Java 1.5+
            Publisher: Canadian Mind Products
            Homepage: http://mindprod.com
          

Available is a simple whois Applet that will probe any server on the Internet to tell you if it is available/up/running. It does a probe via ICMP and UDP echo port 7. IT also probes the home HTML page via port 80. As a side effect, it will tell you the IP address given the host name, or the host name given the IP address.

You can also run it as a standalone utility:

java -jar available.jar