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When using it appears that my ISP is blocking every port. I am attempting to run a web server which works fine locally. I asked a previous question (here) regarding using different ports other than 80 but they all seem to be blocked.

Is this site a valid tool for checking on the ports or could they still be usable? Also, I am using a router, as well as an ISP provided modem. Could one of these devices be causing the problem?


And the final question remains. Why would the site say those high ports are blocked but then allow me to communicate over them?

Unless someone can verify I am just going to assume they don't care about those insanely numbered ports just like an ISP.

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I got my web server to work globally by using a high port (5 digits) the site tells me it is blocked. Maybe the site just doesn't know what to do with crazy port numbers? – sealz Jan 15 '12 at 7:05
Considering the default port for a website is 80, so for example the true address of this website is your ISP is not actually blocking those ports, the website you reference cannot get a response back from say your Apache installation. – Ramhound Jan 19 '12 at 17:19
up vote 1 down vote accepted

To be absolutely sure, you should connect your workstation directly to the modem provided by the your ISP, bypassing the router and running the test again. If you're on a residential plan, I wouldn't be surprised that the ISP is blocking the ports. However, if connecting your workstation directly does work, that would mean your router is not doing port forwarding properly.

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I fixed port forwarding and can access globally, but still says that port is blocked by the ISP. What would be the reason behind this? – sealz Jan 15 '12 at 7:17
Another way you can check if your site is availble to the world is by using the Tor Browser Bundle. It doesn't require setup, so it will take you 2 minutes get it running. – phil Jan 15 '12 at 8:02

Often an ISP will offer a separate plan for people who intend on running a web server. They may enforce this by blocking common web hosting ports like port 80, and use traffic monitoring to look for "suspicious" traffic. The reasoning for this is that they don't want to risk someone using a lower tier connection with less bandwidth hosting a server that ends up getting lots of hits and clogging the pipe, so to speak. Often home internet plans will also be more configured for high download rates but very slow upload rates. For people connecting to your server, they likely will suffer a very slow connection rate. Usually this will be spelled out in your Acceptable Use Policy when you sign up for the service.

If you want to host a server online, you may need to contact your ISP and ask what plans they have available for people who want to host a server. They likely have a business tier of plans that do not have the port blocking.

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