DC++

List of users suddenly disappeared

Asked by Aziz

Hi there,

I connect to my college's dc++ network. Last Thursday night it worked as normal but the morning after, when I connect, It says "connected" but it does not display anything in the users window. It is completely blank. I went and tried other Ethernet ports on campus but same problem. I was thinking that for whatever reason I somehow got blocked so I tried a new computer that has never connected to dc++ and I tried it on some other random port on the other side of campus. Still no users listed. I tried passive connection but still nothing. Now heres the really odd thing. I connect from outside the dorms and the method I use is the following format,

[ipaddress of hub]:5000

It has worked for about a year now. The people inside the dorms where the server is located just type in the ip address and it works. I have confirmed that they are still receiving the user list. So I get nothing but everyone in the dorms have no problems. I have tried apexdc++ just to confirm that it isnt dc++ but apex also gives the same odd behavior.

What could have caused this? I ran Wireshark on it so if anyone wants I can submit the capture file so someone can take a look at it. I ran nmap and confirmed that the host is up and port 5000 is open.

Thanks for reading,

Aziz

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Pirre (pierreparys) said : 		#1

Try to make a connection to a few normal public hubs and if that works you need to bribe your campus network admins with a beer as it's more then likely that they have putted a filter then :)

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Aziz (chaudhryaziz) said : 		#2

Ok I did more research. You are correct in that the public hub has the same error. Looking more closely at Wireshark, I see that when i connect to the dc++ network, my pc and the server establish a successful tcp connection and then exchange two packets. If they were doing filtering, why would there be a successful connection? Remember that the client says "connected" its just that I cannot see any users in the list, it is completely blank.

If there is filtering being done can anyone give me info on how they are performing the filtering? I am curious to learn more about networking.

Is there anyway around the filter if there is one?

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Pirre (pierreparys) said : 		#3

I asume you tryed a few public hubs and they all have the same problem ?

Regarding your questions:

Indeed when a filter is beeing used it will need something to filter on so a few packets are echanged untill the filter finds a match (like the nmdc connect string) and they can then just block further echange.

If you are using a recent client and want to try something (enable under Settings/Security the 3 options before trying and restart if you needed to change them), then try to connect to adcs://devpublic.adcportal.com:16591

This is a adc hub that uses a different protocol and its is also encrypted so you should be able to connect there succesfully when this is a blocking issue :)

And no when a decent packet inspection system is used there is not alot you can do ...

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