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I use a VPN tunnel to connect to my work network and then SSH to connect to my work PC running cygwin. Once logged in I can attach to a screen session and everything works great.

Now, after a while, I walk away from my computer and sooner or later, the VPN tunnel times out. The SSH connection on each end eventually times out and then I eventually come back to my computer to do some work. Theoretically, this should be a simple matter of just restarting the VPN, reconnecting via SSH, and then running "screen -r -d".

However apparently when the sshd daemon times out on the cygwin PC, it leaves the screen session in some kind of hung state. I can reproduce a similar hung state by clicking the close box on a cygwin bash shell window while it's running a screen session.

Is there any way to get the screen session to recover once this has happened, so that I don't lose anything?

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With a great deal of experimentation, I was able to recover the screen session as follows:

  1. Lookup the PID of the server screen process: ps | grep screen
  2. Send the server a HUP signal: kill -1 <PID>
  3. Run a screen client: screen -r -d
  • Thank you! I thought that not being able to reattach was an inherent limitation of Cygwin's screen. This works beautifully! When I execute ps | grep screen the first time, though, I see two processes, a parent and a child. Your solution works iff I send the HUP signal to the child. – garyjohn Jan 12 '11 at 3:06
  • @garyjohn: I believe that the child is the server if you haven't detached when you first launched screen. At least that's what it looked like when I viewed it in Process Explorer. When I detached, the parent process went away and the child remained. Is that what you're seeing? – Mikey Jan 12 '11 at 6:24
  • My test wasn't exactly the same as yours, but I think the results are the same. I ssh'd from another computer using PuTTY, executed screen, then closed PuTTY. That simulated the rude disconnections I usually suffer. Then I ssh'd as before and executed pstree, which showed the two screen instances still running. When I sent HUP to the child, the parent died and the child became inherited by PID 1. – garyjohn Jan 12 '11 at 7:07

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