Here's a handy tool I use all the time, handy for troubleshooting eDirectory/NetWare services, GroupWise MTA/POA ports, etc.
Often, you want to see if a particular port on a given host is open. Like "ping", it's nice to know if something is alive when you're trying to troubleshoot a possible communications problem. With IPPortCheck, you can effectively "ping" a given port on a give host. If you get an "alive" response, you know the communications channel is open.
I use this to test firewall configurations or if I can reach a particular service on a host.
PING is a nice tool to check to see if a particular host is alive, but, as an ICMP request, which often can be blocked across networks, it doesn't confirm necessarily that the host isn't up. IPPortCheck sends a TCP request to the target, and will respond to it if you know the specified port is allowed through.
IPPortCheck (host) (port)