We have an application that works requires, say inbound port 103 (example). It is not working, and the programmers think it is because that inbound port is blocked by either a firewall or an access list on a router.
Without access to these devices, how is it possible to answer this? We can, of course ,try telnetting to that port from the outside. But is there anything else, and more specifically is there anything that will tell us exactly *where* and *why* that port is blocked?
Regards
There is a utility available for UNIX/LiNUX systems named 'tcptraceroute', assuming the port is tcp. I have used it in the past and found it very helpful in finding where a port is blocked when it is outside of your control.
Thanks. For anyone that's interested, a Windows version can be found here.
One thing that seems to stand out is that, if the port is indeed blocked, the tracetcp utility will give you the last hop at address until the packet is blocked, showing you at which point the potential issue is.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required