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Firewall: find out what ports are open





ocalhoun
I'm getting to the internet through a wifi hot spot, and it was working "well enough" before, but all at one time, my e-mail program (thunderbird) and my torrent downloaders (FDM and bittorrent) stop working entirely. The torrents simply fail to connect to the trackers, and the e-mail gives me an error message saying "connecting to the server failed: server replied: ". My best theory is that the wifi hot spot I'm using has blocked additional ports on their firewall. Does anybody here know some software I could use to determine what the hot spot will allow and not allow for incoming/outgoing traffic?

I'm going to try a completely different hot spot in 3 days, to see if that solves the problem, in which case I'll complain to the people who run this hot spot (and charge me for it).
Stubru Freak
ocalhoun wrote:
I'm getting to the internet through a wifi hot spot, and it was working "well enough" before, but all at one time, my e-mail program (thunderbird) and my torrent downloaders (FDM and bittorrent) stop working entirely. The torrents simply fail to connect to the trackers, and the e-mail gives me an error message saying "connecting to the server failed: server replied: ". My best theory is that the wifi hot spot I'm using has blocked additional ports on their firewall. Does anybody here know some software I could use to determine what the hot spot will allow and not allow for incoming/outgoing traffic?

I'm going to try a completely different hot spot in 3 days, to see if that solves the problem, in which case I'll complain to the people who run this hot spot (and charge me for it).


If you're on Linux, it has a port scanning tool. I don't know if you're on Windows.
ocalhoun
Port scanning tools are common, but they are mostly intended to find out what ports are open on a specific remote server, or your local computer. I can't find any that determine the open ports on a firewall in between the two.
bloodrider
What you're asking it isn't quite simple.
The purpose of a firewall is to protect the ports so you can't see if they are open or not, only if you've authorization.
You may try some software like, http://www.nessus.org/, you may be lucky but I wouldn't expect too much, as probably they have a good firewall and correctly configured...
[FuN]goku
i can only think of port scans, in which case, you should use nmap.
TomGrey
I might have a similar problem with my uTorrent, but don't really understand any implications of ports, or random ports, or choosing a port.

Is there a good brief summary of ports and bittorrents (esp. uTorrent)?
ocalhoun
^I'm sure you can find one easily if you google it. I think that the ISP here is filtering out torrent transfers by some method other than port blocking though. Changing the port used randomly does not solve the problem.

Oh, and I tested it at another location, and everything worked exceedingly well, so this hot spot is definitely blocking it.
ProtocolGeek
Wifi hot spots can differ greatly in what ports they allow their users to communicate on or not.

To figure out if ports are blocked, try http://www.firebind.com

This site was specifically designed as an "outbound path scanner" to test outbound ports. You can use it to test any of the 65535 TCP ports to see if your machine can successfully reach the internet using that port. If the test is successful, then your application should be able to use that port as well.

Unlike a port scanner, Firebind doesn't send packets to an IP address of your choice. Instead it talks solely to the Firebind server on the TCP port you choose to tell you whether your PC can communicate to the Firebind Server (and hence the Internet) on that given port. For example, if you want to use Remote Desktop and need to test TCP port 3389, you go to the Firebind web client and enter that port. The Firebind web client on your browser then sends a message over port 80 to the Firebind Server (since that port is almost always open), and tells the Firebind Server to listen for traffic on port 3389. Then the client sends a packet to the Firebind Server on port 3389, and if the response from the server comes back to the client (your machine) intact, you know the port isn't being blocked.

ProtocolGeek
AftershockVibe
This site gives a nice web-based "firewall test". No additional software installation, works from the outside. Probably exactly what you're looking for! Very Happy
http://www.auditmypc.com/firewall-test.asp

Don't be put off by the domain name, it's good stuff!

Edit: Oh, and the easiest way to work out what is being blocked by the proxy is probably to run the test again at home and compare the results.
sith
Didn't mention anything about your default os firewall. Try the default configuration before moving to another tool. It might be possible the configuration is affecting your outbound traffic somehow.
Diablosblizz
I believe this is what you may be looking for: http://www.grc.com/x/ne.dll?rh1dkyd2.

If it doesn't work, google ShieldsUp!
Hogwarts
On your local computer, just install nmap and try to portscan somewhere you know to have X, Y, Z ports open -- such as a temporary home server.

In doing this, you can see which ports are allowed/blocked by the transparent proxy (it's not a firewall, really) as the ports will appear closed on the hotspot (although not from anywhere else)
kmaliagkas
ocalhoun wrote:
I'm getting to the internet through a wifi hot spot, and it was working "well enough" before, but all at one time, my e-mail program (thunderbird) and my torrent downloaders (FDM and bittorrent) stop working entirely. The torrents simply fail to connect to the trackers, and the e-mail gives me an error message saying "connecting to the server failed: server replied: ". My best theory is that the wifi hot spot I'm using has blocked additional ports on their firewall. Does anybody here know some software I could use to determine what the hot spot will allow and not allow for incoming/outgoing traffic?

I'm going to try a completely different hot spot in 3 days, to see if that solves the problem, in which case I'll complain to the people who run this hot spot (and charge me for it).



You are unlucky, unfortunately. Because the user of the wifi hot spot has disable the UPnP. For that reason you were able to work on every port and now you can't. The best way is to find the username and password of the wifi hot spot and create port forward rules for your applications.
Hogwarts
kmaliagkas wrote:
You are unlucky, unfortunately. Because the user of the wifi hot spot has disable the UPnP. For that reason you were able to work on every port and now you can't. The best way is to find the username and password of the wifi hot spot and create port forward rules for your applications.

No it wouldn't be, because you would end up in jail Rolling Eyes
Stubru Freak
Hogwarts wrote:
kmaliagkas wrote:
You are unlucky, unfortunately. Because the user of the wifi hot spot has disable the UPnP. For that reason you were able to work on every port and now you can't. The best way is to find the username and password of the wifi hot spot and create port forward rules for your applications.

No it wouldn't be, because you would end up in jail Rolling Eyes


Not if you find out by asking them.
AftershockVibe
kmaliagkas wrote:
You are unlucky, unfortunately. Because the user of the wifi hot spot has disable the UPnP. For that reason you were able to work on every port and now you can't. The best way is to find the username and password of the wifi hot spot and create port forward rules for your applications.


Errr.... uPnP only works if the speicifc application supports it, it doesn't just open all incoming ports. While bitTorrent clients might request an open port (incoming), an email client won't since all their traffic is outgoing.
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