So often in the past I had to spend time troubleshooting connectivity during product installs. At the end you always come down to testing the ports with Telnet.
So often I have gone to use Telnet to find it is not installed, and I am not able to install due to permissions. So I end up finding the right admin who can do it, which all takes time. Telnet is pretty basic too, but there is a better way, this was especially useful when I had a project to test ESXi connectivity to hundreds of ROBO sites during deployment, it meant we could script in Powershell a basic connectivity test.
So the command is
Test-Netconnection -Computername FQDN -Port xx
This Test-Netconnect has lot more commands as well to make it a really powerful tool. You can start to replace those ping, tracert, telnet commands we have been using for year. Check out this link for more info,
This code example shows how easy it is to run!
Check my firewall table for vSphere products http://vPorts.Info