Port tester?

[syee]

Does anyone know of any software tools that are available (preferably freeware, but doesn't have to be) that will allow me to test whether a specific port is open?

I'm trying to troubleshoot an issue with one of our applications that uses a specific UDP port. The client is reporting that they cannot perform a specific task (which uses UDP port 1450) while connected via a VPN but this works when they are connected locally.

I was looking to see if there are any tools that will allow me to send a message or some kind of data through a particular UDP port and be able to tell me on the other side whether the message was received.

Any suggestions anyone?

 

[theblaznee]

You can't do much when it comes to udp unfortunately..

Check if your VPN tunnel allows IP or just TCP in its access rule.. It's probably the latter, and that's why you have problems..

You do have other types of connections to the server through the VPN tunnel right?

 

[spidey07]

nmap, you can check certain ports

 

[syee]

Yep...we use a bunch of other ports...SQL Server is one that comes to mind (1433 TCP). I'll have to see if they can perform any of the other tasks. Most of the connections through our client application uses TCP...I'll have to get them to test out some other UDP specific features....

Thanks for the info theblaznee!

 

[n0cmonkey]

If you're on the machine that should have the open port (for Windows): netstat -an (if using a unix-like system: netstat -an | grep PORT#).

 

[theblaznee]

The easiest way to test if a certain tcp port works is to use the universally availiable program "telnet" 🙂.. All platforms has this command.. All you have to do is go on the computer that is performing the connection and write ex:

telnet 100.10.11.2 1433

If you want to test tcp port 1433...

If it doesn't work, then it'll time out or come out with a "connection denied" type message.. If the screen goes black or you get another prompt of some kind, then the port in questions works from end to end...