[cups.general] Getting capability info from IPP printers

Michael Sweet msweet at apple.com
Tue Feb 19 10:38:41 PST 2013 

Till,

On 2013-02-19, at 1:22 PM, Till Kamppeter <till.kamppeter at gmail.com> wrote:
> Another question:
> 
> If I do not set the IPP version to 1.1 via
> 
> ippSetVersion(request, 1, 1);
> 
> the printer reports
> 
> server-error-version-not-supported
> 
> How do I find the correct IPP version for the request if I do not know
> the printer's IPP version?

If you get server-error-version-not-supported, retry the query using IPP/1.1.

> Is there an automatic mode?

No.

> Can I get a list of all IPP versions which the currently running CUPS supports so that I can simply go through all of them beginning with the newest until the printer accepts?

No, there is no API for that, but if you are using the newer ippSetVersion API then you have to be running CUPS 1.6 or later, which supports IPP/1.x and IPP/2.x.

But really in this case you just care about what the printer supports - just try 2.0 and if that fails try 1.1.  Don't bother trying 1.0, it just means the printer manufacturer didn't update beyond that experimental (and obsolete) version and it is highly unlikely you will be able to do anything useful with it.  2.1 and 2.2 just target different protocol feature sets, but fundamentally anything you do as a client in a 2.1 or 2.2 request can be done in a 2.0 request - the version numbers just identify (grossly) what the server can do, with the IPP Everywhere and JPS3 changes that came after IPP/2.0 allowing you to learn about supported features (document object, etc.) more easily.

> Which version CUPS uses by default?

ippGetVersion will do it, but for CUPS 1.6 and later you'll always get 2.0 from ippNewRequest.

> My CUPS version is 1.6.1 in Ubuntu Raring.

Have you looked at the new destination APIs?  They are really intended to support this kind of usage (discovery, query for capabilities, and support job submission and management) without you needing to write a lot of extra code...


> 
>   Till
> 
> On 02/19/2013 06:35 PM, Michael Sweet wrote:
>> Till,
>> 
>> First, you can trim requested-attributes to just:
>> 
>>    job-template
>>    printer-description
>>    media-col-database
>> 
>> since all of the -default and -supported values are covered by the job-template group.
>> 
>> Second, you need to use IPP_TAG_KEYWORD when you add the requested-attributes strings, not IPP_TAG_NAME...
>> 
>> 
>> On 2013-02-19, at 10:47 AM, Till Kamppeter <till.kamppeter at gmail.com> wrote:
>> 
>>> Hi,
>>> 
>>> to allow driverless printiung on network-connected printers, especially
>>> from mobile devices I want to poll capability information from the
>>> printer, where I want to support IPP printers with known PDLs, like
>>> PostScript, PCL, IPP Everywhere, ... The program should then
>>> automatically generate a PPD file or at least select the most suitable
>>> generic one, depending on how much info the printer provides.
>>> 
>>> Using ipptool of CUPS I have no problem to poll info from IPP printers,
>>> running
>>> 
>>> ipptool -X <IPP URI of the printer> cap.ipptool
>>> 
>>> cap.ipptool contains:
>>> 
>>> ----------
>>> IGNORE-ERRORS yes
>>> {
>>>       NAME "Get printer attributes using Get-Printer-Attributes"
>>>       OPERATION Get-Printer-Attributes
>>>       GROUP operation-attributes-tag
>>>       ATTR charset attributes-charset utf-8
>>>       ATTR language attributes-natural-language en
>>>       ATTR uri printer-uri $uri
>>>       ATTR keyword requested-attributes
>>> job-template,printer-description,printer-resolution-supported,print-color-mode-supported,print-quality-supported,media-supported,media-default,media-ready,output-bin-supported,finishings-supported,color-supported,sides-supported,number-up-supported,page-ranges-supported,all,media-col-database
>>> }
>>> ----------
>>> 
>>> Now I want to poll with my own C program. It contains:
>>> 
>>> ----------
>>> char *uri;
>>> http_t *http;
>>> ipp_t *request, *response;
>>> int i;
>>> char scheme[10], userpass[1024], host_name[1024], resource[1024];
>>> static const char * const requested_attrs[] =
>>>   {
>>>     "printer-description",
>>>     "document-format-supported",
>>>     "color-supported",
>>>     "pages-per-minute",
>>>     "pages-per-minute-color",
>>>     "media-supported",
>>>     "media-ready",
>>>     "media-default",
>>>     "media-type-supported",
>>>     "media-source-supported",
>>>     "media-col-database",
>>>     "sides-supported",
>>>     "sides-default",
>>>     "output-bin-supported",
>>>     "output-bin-default",
>>>     "finishings-supported",
>>>     "finishings-default",
>>>     "print-color-mode-supported",
>>>     "print-color-mode-default",
>>>     "output-mode-supported",
>>>     "output-mode-default",
>>>     "print-quality-supported",
>>>     "print-quality-default",
>>>     "printer-resolution-supported",
>>>     "printer-resolution-default",
>>>     "copies-supported",
>>>     "copies-default",
>>>     "all"
>>>   };
>>>   uri_status = httpSeparateURI(HTTP_URI_CODING_ALL, uri,
>>> 				 scheme, sizeof(scheme),
>>> 				 userpass, sizeof(userpass),
>>> 				 host_name, sizeof(host_name),
>>> 				 &(port),
>>> 				 resource, sizeof(resource));
>>>   if (uri_status != HTTP_URI_OK)
>>>     goto fail;
>>>   if ((http = httpConnect(host_name, port)) ==
>>> 	NULL) {
>>>     goto fail;
>>>   }
>>>   request = ippNewRequest(IPP_GET_PRINTER_ATTRIBUTES);
>>>   /*ippSetRequestId(request, (CUPS_RAND() % 1000) * 137 + 1);*/
>>>   /*ippAddSeparator(request);*/
>>>   /*ippSetVersion(request, 1, 1);*/
>>>   /*ippAddString(request, IPP_TAG_OPERATION, IPP_TAG_CHARSET,
>>>     "attributes-charset", NULL, "utf-8");*/
>>>   /*ippAddString(request, IPP_TAG_OPERATION, IPP_TAG_LANGUAGE,
>>>     "attributes-natural-language", NULL, "en");*/
>>>   ippAddString(request, IPP_TAG_OPERATION, IPP_TAG_URI,
>>> 		 "printer-uri", NULL, p->uri);
>>>   /*ippAddString(request, IPP_TAG_OPERATION, IPP_TAG_NAME,
>>>     "requesting-user-name", NULL, cupsUser());*/
>>>   ippAddStrings(request, IPP_TAG_OPERATION, IPP_TAG_NAME,
>>> 		  "requested-attributes",
>>> 		  sizeof(requested_attrs) / sizeof(requested_attrs[0]),
>>> 		  NULL, requested_attrs);
>>>    /*int status = cupsSendRequest(http, request, resource,
>>> ippLength(request));
>>>     response = cupsGetResponse(http, resource);*/
>>>   response = cupsDoRequest(http, request, resource);
>>>   if (response == NULL) {
>>>     httpClose(http);
>>>     goto fail;
>>>   }
>>>   printf("cups-browsed: Remote printer %s: %s (%s)\n",
>>>          p->uri, ippErrorString(cupsLastError()),
>>> 	   cupsLastErrorString());
>>>   ipp_attribute_t *attr;
>>>   attr = ippFirstAttribute(response);
>>>   while (attr) {
>>>     printf("Attr: %s\n",
>>>            ippGetName(attr));
>>>     for (i = 0; i < ippGetCount(attr); i ++)
>>> 	printf("Value: %s\n",
>>> 	       ippGetString(attr, i, NULL));
>>>     attr = ippNextAttribute(response);
>>>   }
>>>   attr = ippFindAttribute(response,
>>> 			    "document-format-supported",
>>> 			    IPP_TAG_ZERO);
>>>   if (attr)
>>>     for (i = 0; i < ippGetCount(attr); i ++)
>>> 	printf("Format: %s\n",
>>> 	       ippGetString(attr, i, NULL));
>>>   else
>>>     printf("Not found.\n");
>>> 
>>>   /* Clean up */
>>>   ippDelete(response);
>>>   httpClose(http);
>>> fail:
>>> ----------
>>> 
>>> With this I always get client-error-bad-request, independent whwther I
>>> run it as shown here or whatever combination of lines which are
>>> currently commented out I activated. I tried with several HP printers
>>> (HP Color LaserJet CM3530 MFP, HP LaserJet P3005, HP OfficeJet Pro 8500
>>> A910) and the Canon iR-ADV C5000s-B1, all with the same result, and all
>>> work with ipptool. I also tried to remove and re-add items from the list
>>> of requested attributes.
>>> 
>>> Note: I am using this code only for directly talking with network
>>> printers, not for remote CUPS queues.
>>> 
>>> Any idea what I am doing wrong?
>>> 
>>>  Till
>>> 
>>> 
>>> _______________________________________________
>>> cups mailing list
>>> cups at easysw.com
>>> http://lists.easysw.com/mailman/listinfo/cups
>> 
>> _________________________________________________________
>> Michael Sweet, Senior Printing System Engineer, PWG Chair
>> 
>> _______________________________________________
>> cups mailing list
>> cups at easysw.com
>> http://lists.easysw.com/mailman/listinfo/cups
>> 
> 
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> cups at easysw.com
> http://lists.easysw.com/mailman/listinfo/cups

_________________________________________________________
Michael Sweet, Senior Printing System Engineer, PWG Chair

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