Has AT&T started blocking outbound ports on mobile data?

**tbessie** · 06-13-2012, 04:01 PM

Hey folks...

As of yesterday, SSH connections to all SSH servers I normally connect to, keep disconnecting if I connect via my AT&T cell phone. The ConnectBot Android SSH client disconnects after 5 to 20 seconds of use, consistently.

This only started yesterday. Before that, I never had a problem with it. It has happened in different parts of the city so it's not connected to a given cell tower. This is still happening today.

When I connect from my phone using any WiFi access point, I do not get disconnected, so it's not a problem with the app nor the target server.

I spoke with a couple of other people, and they also are having trouble with disconnects when they use ports out of the usual set of consumer ones used for web and ftp services.

I called AT&T, got to Tier 2 Support, they spoke with Tier 3 support, and Tier 3 told them nothing of interest. That I should "reinstall my ssh app" - useless.

Does anyone know if AT&T has made an unannounced policy change about concerning blocked ports? Perhaps a process on their servers that seeks out various ports it "doesn't like" and kills the connections?

- Tim

**formercanuck** · 06-13-2012, 05:34 PM

I don't think so... its working OK for me.

Sent from my SAMSUNG-SGH-I777 using HowardForums

**tbonecopper** · 06-13-2012, 07:28 PM

Is the SSH app sending a keep alive signal to your box? It may be timing out due to packet loss or something at the network.

May sound odd, but from a terminal on a computer have you:

vi (or nano, or w/e you like really) /etc/ssh/ssh_config

and add

ServerAliveInterval <time in seconds>

And tried again from your app to see if it may be the network not relaying the packets needed to keep your connection from the app alive?

**tbessie** · 06-13-2012, 08:28 PM

Originally Posted by tbonecopper

Is the SSH app sending a keep alive signal to your box? It may be timing out due to packet loss or something at the network.

May sound odd, but from a terminal on a computer have you:

vi (or nano, or w/e you like really) /etc/ssh/ssh_config

and add

ServerAliveInterval <time in seconds>

And tried again from your app to see if it may be the network not relaying the packets needed to keep your connection from the app alive?

The SSH client should be sending keepalives of some sort (or at least, one hopes).

I have no control over my ISP's SSH server, and nothing has changed on their end. The wild card here is AT&T - what might they have changed that would make all SSH connections be terminated? I'm using ConnectBot on my android phone, not a native Linux client that would use anything in /etc on the phone, if you're suggesting ssh client parameter modifications as opposed to server config.

In case your interested, what I'm experiencing has been verified somewhat by a response to my posting on the AT&T forums, which makes it appear that AT&T is doing something funny now...

http://forums.att.com/t5/Data-Messag...t/false#M58669

- Tim

**blacknoi** · 06-14-2012, 02:51 PM

Interesting. I am not sure if my situation is exactly the same but something started happening tuesday with me and blocked ports.

On 3G/4G on my iphone, I can authenticate to a particular website, however when I try and download some content that requires my credentials I get an access is denied... as if my credentials arent being passed through.

Change it to wifi and its fine.

I have a home VPN connection set up and if I put my iphone on VPN, I can download the content w/o getting the access is denied message.

Something is definitely being blocked when I'm using the raw 3G/4G connection that works fine via wifi or VPN.

I conduct the same test on my verizon iphone and no issues. Only on my AT&T iPhone.

**scaredpoet** · 06-14-2012, 03:47 PM

SSH seems to be working fine for me, no issue here.

**tbessie** · 06-14-2012, 04:02 PM

Originally Posted by scaredpoet

SSH seems to be working fine for me, no issue here.

What ssh client are you using?

I'm on a Galaxy Nexus using ConnectBOT.

Could be that AT&T is only disconnecting unbranded phones (i.e. ones you didn't buy from them), which would be very sucky.

- Tim

**awj223** · 06-15-2012, 02:39 PM

Originally Posted by tbessie

What ssh client are you using?

I'm on a Galaxy Nexus using ConnectBOT.

Could be that AT&T is only disconnecting unbranded phones (i.e. ones you didn't buy from them), which would be very sucky.

- Tim

OP, I think something's wrong with your SSH client. Did you try uninstalling it and then reinstalling it? Also, you should try VX Connectbot - the Connectbot fork.

In any case, I'm not having any problems on my Nexus One.

**-banned-** · 06-15-2012, 02:51 PM

Originally Posted by formercanuck

I don't think so... its working OK for me.

do u live work or play in his city..??

**-banned-** · 06-15-2012, 02:57 PM

Originally Posted by blacknoi

On 3G/4G on my iphone, I can authenticate to a particular website, however when I try and download some content that requires my credentials I get an access is denied... as if my credentials arent being passed through.

Change it to wifi and its fine.

seems like they are blocking out secured links..?? http(s) sites maybe..?? When you change to wifi aka different ISP, its fine which common sense tells you its an AT$T issue…

If you know someone with an AT$T android or iPhone that has the ability to create a wifi hotspot, jump off their wifi signal and see if it still blocks you out…

**tbessie** · 06-15-2012, 03:16 PM

Well, today it seems to have started working again. On the AT&T forums, someone else who was having similar connectivity issues (tho' with a music streaming app - random disconnects starting just this week) found that this morning they started working again.

I checked, and sure enough, mine started working again too.

Last night, I checked with other phones I had (Nexus One, Nokia N86) and had the same exact problems (didn't work on AT&T's network, worked on WiFi).

This tells me that it is highly likely that:

1. AT&T changed some configuration for certain accounts (based on what properties, I don't know; definitely not by phone type; perhaps by account usage patterns, location, etc.)

2. AT&T undid those configuration changes today

For those saying it was my SSH client, that wasn't the case, as this SSH client had worked fine forever, until just this week, when FTP transfers were also being terminated. Also, the Symbian SSH client was working fine before, but not last night when I tried it, but then was working again this morning as well. So, nothing to do with the client, almost certainly everything to do with AT&T's configuration, probably targeting certain users.

My question still is: why did they do this in the first place? Probably will never get an answer from them.

- Tim