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  #1  
Old 21st June 2009, 20:08
anw anw is offline
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Default putty Connection Seemingly Drops

Odd problem: when I'm working with putty from my home office to a server I have on the public internet, after a short period of time the terminal interface on the client quits responding. Here is some parameterization:

1. I've tried all sorts of keep-alive options on the client and the server. This just started happening within the last week; prior to that, I had tcp keep-alives in the server "on" and set to 900 seconds in the putty client. Since then, I've tried all sorts of various options and no change.

2. This does not happen when logging in to the same server from work. The session will remain stable for days regardless of whether I type into it or not.

3. I set debugging to DEBUG3 on the server and wrote a simple bash script that will print the time to the putty screen, wait 2 seconds, then print the time again, so I could narrow down exactly when it occurred and follow what was happening in the logs. The client log has nothing except the time being received. The server has very verbose output, but nothing I can see that looks unusual. For a window that printed the last "date" output at 13:50:03, here is the server output log that brackets that time (note the gap; evidently sshd saw nothing happen):
Quote:
Jun 21 13:48:46 ops sshd[6647]: debug2: fd 3 setting O_NONBLOCK
Jun 21 13:48:46 ops sshd[6647]: debug1: Bind to port 22 on 0.0.0.0.
Jun 21 13:48:46 ops sshd[6647]: Server listening on 0.0.0.0 port 22.
Jun 21 13:48:46 ops sshd[6647]: debug2: fd 4 setting O_NONBLOCK
Jun 21 13:48:46 ops sshd[6647]: debug1: Bind to port 22 on ::.
Jun 21 13:50:30 ops sshd[6647]: debug3: fd 4 is not O_NONBLOCK
Jun 21 13:50:30 ops sshd[6746]: debug1: rexec start in 4 out 4 newsock 4 pipe 6 sock 7
Jun 21 13:50:30 ops sshd[6647]: debug1: Forked child 6746.
Jun 21 13:50:30 ops sshd[6647]: debug3: send_rexec_state: entering fd = 7 config len 685
Jun 21 13:50:30 ops sshd[6647]: debug3: ssh_msg_send: type 0
Jun 21 13:50:30 ops sshd[6647]: debug3: send_rexec_state: done
Jun 21 13:50:30 ops sshd[6746]: debug1: inetd sockets after dupping: 3, 3
putty doesn't seem to know the connection has dropped. If I let it go for hours, putty will eventually come back and say the connection has timed out, but this is way after it has quit responding.
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  #2  
Old 22nd June 2009, 15:21
falko falko is offline
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Default

Quote:
Originally Posted by anw View Post
1. I've tried all sorts of keep-alive options on the client and the server. This just started happening within the last week; prior to that, I had tcp keep-alives in the server "on" and set to 900 seconds in the putty client. Since then, I've tried all sorts of various options and no change.
Set it to 30 seconds and try again.
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  #3  
Old 22nd June 2009, 15:36
anw anw is offline
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I'll try it as soon as I get back to my office this afternoon.

Thanks!
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Old 26th June 2009, 02:52
anw anw is offline
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I tried 30, no change. I also temporarily shut down ftp on the server, and tried running sshd on port 21, still no change. I rebooted my (home) router and rooted through all the networking stuff (logs, displays, netstat, etc.). I can't see anything wrong, but my home router seems to know when the connection gets torn down, as it removes it from its list of connections. Neither server seems to know the connection is gone.
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Old 26th June 2009, 04:08
id10t id10t is offline
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Do you have a decent isp? They may be seeing long encrypted sessions and killing them trying to fight piracy, etc. Or it may be your home router doing something...
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Old 27th June 2009, 18:22
anw anw is offline
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I'm going to call my ISP today. I don't think its my router; its been working fine for two or three years, and I rebooted my router as well.
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Old 28th June 2009, 04:10
anw anw is offline
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Evidently my Linksys home router went bad. I plugged my cable modem directly into a laptop and everything worked; move back to the main access switch, everything worked; moved to the main router (I also had a wireless router plugged in for my home network), and I got the intermittent problem. So I just took my wired router out of the network (my wireless router has a built-in 4-port switch, which is adequate since I only have a couple of circuits going to other main switches), and all seems good.

The router must have a momentary-glitch problem, because I could get on the internet fine and didn't seem to have any other problems, so what I don't understand is why, if I have putty set up to not do keepalives, it would drop the circuit. I don't see why putty would even know if the router momentarily glitched.
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