Cygwin shells closing when launched by a telnet server client in Windows 7

Cygwin shells closing when launched by a telnet server client in Windows 7

[Clayton Evans]

I am in the process of upgrading to a new machine.  This machine is used as a compute server, where users telnet to the machine, start up a Korn shell and run compute intensive programs from the Korn shell.  The current machine is running Cygwin 1.5 and Windows XP 64 bit.  This process has worked for years.  The new machine is running Cygwin 1.7 and Windows 7 64 bit.  After telneting to the new machine, mksh.exe appears to start after some pause, show it's prompt and then exits, returning to the command prompt within the telnet session.  This behavior makes me think that no input stream is getting connected to the shell and the shell exits.
Both machines are using Microsoft's Telnet Service.  I have tried ash.exe, bash.exe, dash.exe and sh.exe.  All the shell programs show their input prompt and then exit to the command prompt
C:\cygwin\bin>mksh.exe -l -i
user@hostname ~
$

C:\cygwin\bin>
The shell commands work fine, when one is locally on the compute server.   I have tried HyperTerminal, putty.exe and Microsoft's telnet client on the client machine and they all give the same result.
There are no entries in the Windows 7 event log.
The Korn shell is working non-interactively when telneted as demonstrated below by having the Korn shell execute a command specific to the Korn shell.
C:\cygwin\bin>mksh.exe -c "whence whence"
whence

C:\cygwin\bin>
I have tried setting the Korn shell to be terminal server aware, peflags -tsaware=true mksh.exe, with no change in the results.

Clayton Evans


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Re: Cygwin shells closing when launched by a telnet server client in Windows 7

[Corinna Vinschen]

On Aug 22 13:46, Clayton Evans wrote:
> I am in the process of upgrading to a new machine.  This machine is
> used as a compute server, where users telnet to the machine, start up
> a Korn shell and run compute intensive programs from the Korn shell.
> The current machine is running Cygwin 1.5 and Windows XP 64 bit.  This
> process has worked for years.  The new machine is running Cygwin 1.7
> and Windows 7 64 bit.  After telneting to the new machine, mksh.exe
> appears to start after some pause, show it's prompt and then exits,
> returning to the command prompt within the telnet session.  This
> behavior makes me think that no input stream is getting connected to
> the shell and the shell exits.

First of all, don't use telnet.  Use ssh.  There's an openssh package
in the distro which provides an sshd server.

> Both machines are using Microsoft's Telnet Service.  I have tried
> ash.exe, bash.exe, dash.exe and sh.exe.  All the shell programs show
> their input prompt and then exit to the command prompt
> C:\cygwin\bin>mksh.exe -l -i
> user@hostname ~
> $
> 
> C:\cygwin\bin>
> The shell commands work fine, when one is locally on the compute
> server.   I have tried HyperTerminal, putty.exe and Microsoft's telnet
> client on the client machine and they all give the same result.
> There are no entries in the Windows 7 event log.
> The Korn shell is working non-interactively when telneted as
> demonstrated below by having the Korn shell execute a command specific
> to the Korn shell.
> C:\cygwin\bin>mksh.exe -c "whence whence"
> whence
> 
> C:\cygwin\bin>
> I have tried setting the Korn shell to be terminal server aware,
> peflags -tsaware=true mksh.exe, with no change in the results.

That flag has nothing to do with this problem.

However, I have no idea how to help with telnet.  I tried to track this
down, and it turns out that a perfectly valid call to WaitForMultipleObjects
with the telnet stdin handle returns with an error "Invalid Handle", while
WriteFile to the telnet pipe performed by the first Cygwin process in a
process tree can break the connection.  You say it worked in 1.5, but
I don't see a difference in the handling of the incoming stdio handles
between 1.5 and 1.7 which would explain that behaviour.


Corinna


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Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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