Re: [Ssh-sftp-perl-users] Detecting connection closed by server.

[Enrique de A. S. <enr...@pc...>]

I will try the different options you have given me.
Thanks,
Enrique.

Mark A. Fuller wrote:
>>I have next problems, sometimes it's possible that ssh server close SSH
>>connection. Then, requests sent by the client has not response, but it
>>is unable to detect it.
> 
> 
> What happens in that case? Does net::ssh die? Or, does it never timeout?  
> 
> I found a few cases where net::ssh dies. I had to surround my net:ssh activity with an "eval" so I could interrogate $@ to see if it died. I also had to collect Perl warnings because net::ssh may issue one or two prior to dieing and those first one or two would be more meaningful than the message when it dies. I did something like this:
> 
> ==========
> @warnings = (); # empty array
> 
> $SIG{'__WARN__'} = sub { $warnings[$#warnings + 1] = $_[0]; };
> 
> eval {
>   # The net::ssh action which may die
> };
> 
> $SIG{'__WARN__'} = 'DEFAULT';
>  
> 
> #-------------------------------------------------------------------------------
> # Write failure response.
> #-------------------------------------------------------------------------------
> if (($#warnings > -1) or (!defined($sftp) or !$sftp) ) {
> 
>   for (@warnings) {
>     print STDERR $_;
>   } 
> 
>   exit 99;
> 
> }
> ========================
> 
> I posted an exact example a few months ago, but I can't get to the mailing list's archive at the moment. You can search for "eval" and look at the few things I posted. 
> 
> If the problem is that your connection never times out, you can do something like this:
> 
> ==================
> eval {
>         local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n required
>         alarm 10;
>         #net::ssh action that may hang
>         alarm 0;
>     };
> if ($@) {
>         die unless $@ eq "alarm\n";   # propagate unexpected errors
>         # timed out
> }
> else {
>         # didn't timeout
> }
> ===================
> 
> You can nest the two evals to protect against either case. But, you want to make sure you don't have a race condition if the command dies and you haven't turned off the alarm yet.
> 
> FWIW, I began using expect.pm to drive my native ssh/sftp/scp binaries. To me it's faster and simpler. The big positive is that if something doesn't work right, I can run the binary and see exactly what my script (using expect.pm) sees. There's no differences between my command line use and what happens in my scripts. I posted an example of how to do this a few months ago too.
> 
> Mark
> 
> 
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