PortQry - Knock Knock! Anyone Home?

PortQryUI

When I run into connectivity problems at work (or anywhere really), I turn to a nice little tool called PortQry and it's buddy PortQryUI.  These tools let me test a connection between two computers by plugging in the address and port number. If you're like me and a lot of other IT folks, you work on networks with lots of firewalls between them.  It's nice and secure, but you can't get anything done!

For instance, one day I came into work with an email in my inbox saying that a user was not able to log into a certain web application.  So naturally, I try it myself first.  The error I got back in the web browser gave me no info - typical to web apps that don't have good error reporting.  So I go digging through the application logs which are java-based, even more fun!  I see a line about connection refused, so I immediately pull out my copy of PortQry and test the connection from this app server to our AD server (where this server goes to authenticate users). Sure enough, the output tells me "Filtered" which means it's hitting a firewall and being dropped.  Long story short, I talk to the firewall guys and they are able to help me solve the problem.

You may wonder why I even bothered using the tool since the web app logs told me the connection was refused.  This is because I don't trust app servers to return an error code that uses industry standard terminology.  The company that built this app could be using ANYTHING to test the connection and they just happen to use the text "connection refused" because that was the only error they felt like putting in that day.  So if you verify the connection with another connection testing tool like this one, you will know for sure there is a connection issue and maybe even know what kind of issue (firewalled or just not responding).

Download the tool, it's two parts, I think they can operate independently though:

1. Command Line
2. Graphical User Interface (GUI or UI)