[cups.development] Printing to CUPS printer via LPR from Embedded System

[Jon Peatfield]

On Mon, 16 Feb 2009, Ian wrote:

> Hello,
>
> I am trying to print to a CUPS printer from an embedded system that supports LPR. When I user a hardware print server (i.e. HP JetDirect) I can print fine, but when I try to use CUPS I get no printout. However, if I try to print from a windows machine to the CUPS printer using LPR it works fine.
>
> This is my /var/log/messages file after first trying to print from the embedded system and then printing from windows:
>
> *************************************
> ---/var/log/messages---
> Feb 14 14:04:13 haroldws08 syslogd 1.4.1: restart.
> Feb 14 14:04:13 haroldws08 kernel: klogd 1.4.1, log source = /proc/kmsg started.
> Feb 14 14:04:35 haroldws08 xinetd[8197]: START: printer pid=8239 from=192.168.2.201
> Feb 14 14:04:35 haroldws08 cups-lpd[8239]: Connection from 192.168.2.201 (IPv4 192.168.2.201)
> Feb 14 14:04:35 haroldws08 cups-lpd[8239]: Receive print job for PRINTER
> Feb 14 14:04:36 haroldws08 cups-lpd[8239]: Error while reading file - No such file or directory
> Feb 14 14:04:36 haroldws08 cups-lpd[8239]: Closing connection
> Feb 14 14:04:36 haroldws08 xinetd[8197]: EXIT: printer status=1 pid=8239 duration=1(sec)
> Feb 14 14:11:47 haroldws08 xinetd[8197]: START: printer pid=8363 from=192.168.2.158
> Feb 14 14:11:47 haroldws08 cups-lpd[8363]: Connection from calws-20.barbereng.com (IPv4 192.168.2.158)
> Feb 14 14:11:47 haroldws08 cups-lpd[8363]: Receive print job for printer
> Feb 14 14:11:47 haroldws08 cups-lpd[8363]: Print file - job ID = 7
> Feb 14 14:11:47 haroldws08 cups-lpd[8363]: Closing connection
> Feb 14 14:11:47 haroldws08 xinetd[8197]: EXIT: printer status=0 pid=8363 duration=0(sec)
> *************************************
<snip>
>
> Any help you might be able to offer would be appreciated.

You don't say which cups version you are using, but at least for 
cups-1.3.x the error message "Error while reading file -" is certainly 
from recv_print_job() in cups-lpd.c ie at about line 1050:

    /*
     * Copy the data or control file from the client...
     */

     for (i = atoi(count); i > 0; i -= bytes)
     {
       if (i > sizeof(line))
         bytes = sizeof(line);
       else
         bytes = i;

       if ((bytes = fread(line, 1, bytes, stdin)) > 0)
         bytes = write(fd, line, bytes);

       if (bytes < 1)
       {
 	syslog(LOG_ERR, "Error while reading file - %s",
                strerror(errno));
         status = 1;
 	break;
       }
     }

so it is failing whiule reading the control-file or a data-file from the 
client.  After getting such an error it gives up on the request so it will 
never actually touch the cups daemon - so those logs are probably 
irrelevant.

Why the fread() or write() is returning < 1 isn't clear, so perhaps adding 
some debugging at about that point will help - or at least tracing the 
cups-lpd process...

Perhaps the lpd control file is 'bad' in some way which cups-lpd objects 
to - but the jetdirect implementation is more relaxed.

I'd suggest changing that section to something like:

    /*
     * Copy the data or control file from the client...
     */

     syslog(LOG_ERR, "About to read file expected %s bytes", count);
     for (i = atoi(count); i > 0; i -= bytes)
     {
       syslog(LOG_ERR, "In loop expecting %d more bytes", i);

       if (i > sizeof(line))
         bytes = sizeof(line);
       else
         bytes = i;

       if ((bytes = fread(line, 1, bytes, stdin)) > 0)
       {
         syslog(LOG_ERR, "fread returned %d", bytes);
         bytes = write(fd, line, bytes);
         syslog(LOG_ERR, "fwrite returned %d", bytes);
       } else {
         syslog(LOG_ERR, "error fread returned %d", bytes);
       }

       if (bytes < 1)
       {
         syslog(LOG_ERR, "Error while reading file - %s",
                strerror(errno));
         status = 1;
         break;
       }
     }

and seeing what logs that produces.

  -- Jon