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Can't show http://localhost or on FF 5


"Firefox can't establish a connection to the server at localhost." "Firefox can't establish a connection to the server at"

Tools > Options > Advanced : Network : Connection : No Proxy

I can ping them okay in a DOS box.

I have the same problem in Ubuntu 14-4 where both machines are connected to a Linksys router (the IBM wireless, the Linux with Ethernet).

Is it a firewall problem? My XP firewall is on but I don't understand how to add a port; with I get: "You can only type a number here."

I'm using FF 5.0 on XP SP3.

Hope you can help, Peter

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kerframil 6 solutions 53 answers

Connecting to doesn't make any sense unless you are trying to connect to an HTTP server (such as IIS or Apache) running on the same system that is running the browser. Pinging doesn't prove anything; the loopback interface will respond to pings but it doesn't mean that you have an HTTP server running locally. Indeed, that would be somewhat unusual (except for web developers who like to have a local server for testing).

Firewalls have nothing to do with it. The loopback interface (on address exists only to allow a machine to communicate with itself via Internet Protocol.

I suspect you are confused as to what you are trying to accomplish. What were you expecting to see when entering that address?

Modified by kerframil

Question owner

I was trying to see what was visible to a 3rd party thru my IP@.

I remember having an Apache server running in the past and finding localhost useful, but I have to agree with everything you said, so:

Thanks, Peter

kerframil 6 solutions 53 answers

OK. If you're worried about what can be 'seen' from another host on the Internet then I can assure you that the loopback interface has nothing to do with it. Have a look at this:


The IP address that appears there is the one you're concerned with. Even then, for tests of this nature to be meaningful, they need to be conducted from an 'external' host i.e. not your PC or any other system on your local network.

Be wary of the security theatre that tends to encumber the discussion of 'open' and 'unopen' ports. Ports don't mean much unless there are active network services that are *bound* to said ports. If your PC is behind a router that performs connection sharing then you likely have nothing to worry about unless (a) the router itself is exposing a service to the Internet that is potentially exploitable [*] (b) it is port forwarding to a service on one of your internal hosts which is not adequately secured or exploitable. On the other hand, if you are 'directly' connected to the Internet - through a cable modem say - you need to be careful and make sure that the XP firewall is enabled (with exceptions disabled unless you have a specific reason).

[*] A contrived example would be accidentally allowing its HTTP based admin interface to be accessed from the Internet at large, not just your internal hosts.

Question owner

So is this normal:

   "Firefox can't establish a connection to the server at " <whatismyip.org>
kerframil 6 solutions 53 answers

Well, no. But there are other similar sites such as whatismyip.com and whatismyipaddress.com. You could try those.

Question owner

What I'm saying is that I entered the result of whatismyip.com and whatismyipaddress.com into FF's address line and got: "Firefox can't establish a connection to the server at ..."