Re: channel_poll() is blocking

[Bart Simpson <b_a_r_t@xxxxxxx>]

Hi Aris,
that sound logical for me, but there is a another problem.
I tried the same test program on different maschines and the result is very strange.


result is only the return value of channel_poll(channel, 0) without the while loop, etc.

case 1:  windowsPc (company) --->   linuxServer (company)   result: -1
case 2:  windowsPc (home)    --->   linuxServer (home)      result:  0
case 3:  linuxPc   (home)    --->   linuxServer (company)   result: works!
case 4:  linuxPc   (home)    --->   linuxServer (home)      result: works!	

(linux ---> linuxServer works always,  windows ---> linuxServer fail, 
but with different results)


Regards,
Thomas




Am 12.05.2010 16:07, schrieb Aris Adamantiadis:
> Hi Thomas,
>
> I discourage you to use channel_read_buffer as this function will be
> deprecated soon. Please use channel_read instead.
>
> Your example is blocking because you're looping several time inside the
> loop. When there is no new data to read, channel_poll returns 0. That
> means that you're doing a channel_read when there's nothing to read,
> hence the blocking behaviour.
>
> I recommend this rewrite:
>
>       while (channel_poll(channel, 0)>  0)
>       {
>           char buf[128];
>           rc = channel_read_buffer(channel, buf, sizeof(buf), 0);
>   	 if(rc<sizeof(buf))
>            buf[rc]='\0'; // 0-ends the string
>           else
>            buf[sizeof(buf)-1]='\0';
>           if  (rc<  0)
>           {
>               channel_close(channel);
>               ssh_disconnect(session);
>               ssh_finalize();
>               return 1;
>           }
>
>           printf("%s\n", buf);
>       }
>   }
>
> Regards,
>
> Aris
> Bart Simpson a écrit :
>    
> > Hello,
> > I wrote a little test program to exec a command on a remote host and
> > read the result from channel.
> > Open session, authentification with public keys, exec command, etc. work
> > all fine.
> > But when I try to read something from the channel with this code part
> > from the examples of libssh,
> > the function channel_poll() is blocking. After a few minutes -1 returned.
> >
> > Do anyone know, whats wrong?
> >
> > ...
> > if  (channel_is_open(channel))
> > {
> >      while (channel_poll(channel, 0)>= 0)
> >      {
> >          buf = buffer_new();
> >          rc = channel_read_buffer(channel, buf, 0, 0);
> >
> >          if  (rc<  0)
> >          {
> >              buffer_free(buf);
> >              channel_close(channel);
> >              ssh_disconnect(session);
> >              ssh_finalize();
> >              return 1;
> >          }
> >
> >          printf("%s\n", (char *) buffer_get(buf));
> >          buffer_free(buf);
> >      }
> > }
> > ...
> >
> >
> > Regards,
> > Thomas
> >
> >      
>