Windows Printer Discovery

I was surprised to find that Windows had automatically detected my printer, even though the printer doesn't talk SMB/NMB and Windows doesn't talk DNS-SD. It turns out that a printer communication protocol called WS-print has been available since Windows Vista.

• Trigger warning: Web Services. XML and SOAP. It's all very 2006.

Discovery

WS-Discovery uses SOAP-over-UDP to discover devices on the network. Thanks to Wireshark, we can see the service transmites a UDP packet to 239.255.255.250 (or ff02::c for IPv6), port 3702:

•    1 <?xml version="1.0" encoding="utf-8"?>
     2 <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:wsd="http://schemas.xmlsoap.org/ws/2005/04/discovery" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:wsdp="http://schemas.xmlsoap.org/ws/2006/02/devprof" xmlns:nprt="http://schemas.microsoft.com/windows/2006/08/wdp/print">
     3   <soap:Header>
     4     <wsa:Action>http://schemas.xmlsoap.org/ws/2005/04/discovery/Hello</wsa:Action>
     5     <wsa:MessageID>urn:uuid:3af4b6f3-50bc-49cc-b9f6-4e37e9d875af</wsa:MessageID>
     6     <wsa:To>urn:schemas-xmlsoap-org:ws:2005:04:discovery</wsa:To>
     7     <wsd:AppSequence InstanceId="53" MessageNumber="2"/>
     8   </soap:Header>
     9   <soap:Body>
    10     <wsd:Hello>
    11       <wsa:EndpointReference>
    12         <wsa:Address>uuid:f6fe2f0a-325f-4454-aa07-0888d60ffa64</wsa:Address>
    13       </wsa:EndpointReference>
    14       <wsd:Types>wsdp:Device nprt:PrintDeviceType</wsd:Types>
    15       <wsd:XAddrs>http://[fe80::221:b7ff:fe88:ced0]:50000/lxkWSdevice</wsd:XAddrs>
    16       <wsd:MetadataVersion>8</wsd:MetadataVersion>
    17     </wsd:Hello>
    18   </soap:Body>
    19 </soap:Envelope>
  

  Already the XML is flying thick and fast. We have to deal with WS-Addressing and Devices Profile for Web Services, not to mention WS-Print itself. Of note are:

  uuid

  within the wsa:Address element, which is the printer's 'Unique identifier' as displayed within Devices and Printers → dell2330 → Properties → Web Services → Troubleshooting Information.

  types

  identify this as a printer

  transport address

  within the xsd:Xaddrs element, which shows upin Devices and Printers → dell2330 → Properties → Hardware → dell2330: WSD Print Provider → Location

Wireshark also shows the client broadcasts a Resolve message for the UUID (to the multicast address), and the client responds with a ResolveMatch packet (to the client's address) containing much the same information as the original broadcast. There is actually a slight difference: the transport address in this response doesn't include the /lxkWSdevice path. Probably just a quirk of the printer's code?

Clients can also initiate a search for a device. python-ws-discovery reveals that the client transmits a Probe message, and the service responds with a ProbeMatches message containing the EndpointReference as above (but again without /lxkWSdevice).

Printing

Back to Wireshark, the client does a HTTP POST to the transport address:

•    1 <?xml version="1.0" encoding="utf-8"?>
     2 <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing">
     3   <soap:Header>
     4     <wsa:To>uuid:f6fe2f0a-325f-4454-aa07-0888d60ffa64</wsa:To>
     5     <wsa:Action>http://schemas.xmlsoap.org/ws/2004/09/transfer/Get</wsa:Action>
     6     <wsa:MessageID>urn:uuid:4ab98165-5095-499d-8222-cd55690eb4c8</wsa:MessageID>
     7     <wsa:ReplyTo>
     8       <wsa:Address>http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</wsa:Address>
     9     </wsa:ReplyTo>
    10     <wsa:From>
    11       <wsa:Address>urn:uuid:8570035b-a8b5-45c0-b0f8-89d70974e534</wsa:Address>
    12     </wsa:From>
    13   </soap:Header>
    14   <soap:Body/>
    15 </soap:Envelope>
  

to which the printer responds:

•    1 <?xml version="1.0" encoding="utf-8"?>
     2 <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:wsx="http://schemas.xmlsoap.org/ws/2004/09/mex" xmlns:wsdp="http://schemas.xmlsoap.org/ws/2006/02/devprof" xmlns:nprt="http://schemas.microsoft.com/windows/2006/08/wdp/print" xmlns:PNPX="http://schemas.microsoft.com/windows/pnpx/2005/10" xmlns:UNS1="http://www.microsoft.com/windows/test/testdevice/11/2005">
     3   <soap:Header>
     4     <wsa:To>http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</wsa:To>
     5     <wsa:MessageID>urn:uuid:02191325-8505-40a1-97fd-c732fbdbc59a</wsa:MessageID>
     6     <wsa:RelatesTo>urn:uuid:9f6331b5-cdf9-44ba-b819-d99364bf9bad</wsa:RelatesTo>
     7     <wsa:Action>http://schemas.xmlsoap.org/ws/2004/09/transfer/GetResponse</wsa:Action>
     8   </soap:Header>
     9   <soap:Body>
    10     <wsx:Metadata>
    11       <wsx:MetadataSection Dialect="http://schemas.xmlsoap.org/ws/2006/02/devprof/ThisDevice">
    12         <wsdp:ThisDevice>
    13           <wsdp:FriendlyName xml:lang="en">dell2330</wsdp:FriendlyName>
    14           <wsdp:FirmwareVersion>NR.APS.N310</wsdp:FirmwareVersion>
    15           <wsdp:SerialNumber>7218W78</wsdp:SerialNumber>
    16         </wsdp:ThisDevice>
    17       </wsx:MetadataSection>
    18       <wsx:MetadataSection Dialect="http://schemas.xmlsoap.org/ws/2006/02/devprof/ThisModel">
    19         <wsdp:ThisModel>
    20           <wsdp:Manufacturer xml:lang="en">Dell</wsdp:Manufacturer>
    21           <wsdp:ManufacturerUrl>http://www.dell.com</wsdp:ManufacturerUrl>
    22           <wsdp:ModelName xml:lang="en">Dell 2330dn Laser Printer</wsdp:ModelName>
    23           <wsdp:ModelNumber>Dell 2330dn Laser Printer</wsdp:ModelNumber>
    24           <wsdp:ModelUrl>http://www.lexmark.com/MD/?func=producthome</wsdp:ModelUrl>
    25           <wsdp:PresentationUrl>http://[fe80::221:b7ff:fe88:ced0]</wsdp:PresentationUrl>
    26           <PNPX:DeviceCategory>Printers</PNPX:DeviceCategory>
    27         </wsdp:ThisModel>
    28       </wsx:MetadataSection>
    29       <wsx:MetadataSection Dialect="http://schemas.xmlsoap.org/ws/2006/02/devprof/Relationship">
    30         <wsdp:Relationship Type="http://schemas.xmlsoap.org/ws/2006/02/devprof/host">
    31           <wsdp:Hosted>
    32             <wsa:EndpointReference>
    33               <wsa:Address>http://[fe80::221:b7ff:fe88:ced0]:4033/Printer1/WebServices</wsa:Address>
    34               <wsa:ReferenceProperties>
    35                 <UNS1:ServiceIdentifier>uri:prn</UNS1:ServiceIdentifier>
    36               </wsa:ReferenceProperties>
    37             </wsa:EndpointReference>
    38             <wsdp:Types>nprt:PrinterServiceType</wsdp:Types>
    39             <wsdp:ServiceId>uri:f6fe2f0a-325f-4454-aa07-0888d60ffa64/Printer1/WebServices</wsdp:ServiceId>
    40             <PNPX:CompatibleId>http://schemas.microsoft.com/windows/2006/08/wdp/print/PrinterServiceType</PNPX:CompatibleId>
    41           </wsdp:Hosted>
    42         </wsdp:Relationship>
    43       </wsx:MetadataSection>
    44     </wsx:Metadata>
    45   </soap:Body>
    46 </soap:Envelope>
  

Of interest are the references to Lexmark. It seems they manufactured this printer for Dell! This also explains the origin of /lxkWSdevice in the transport address.

Further communication takes place using a new URL, given for the uri:prn endpoint in this message. (Weirdly, Windows uses IPv4 from this point onwards, but I'll assume that communication over IPv6 would produce similar results. Here's an example:

•    1 <?xml version="1.0" encoding="utf-8"?>
     2 <soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:UNS1="http://www.microsoft.com/windows/test/testdevice/11/2005" xmlns:pri="http://schemas.microsoft.com/windows/2006/08/wdp/print">
     3   <soap:Header>
     4     <wsa:To>http://192.168.0.6:4033/Printer1/WebServices</wsa:To>
     5     <wsa:Action>http://schemas.microsoft.com/windows/2006/08/wdp/print/GetPrinterElements</wsa:Action>
     6     <wsa:MessageID>urn:uuid:a74b1759-ac13-4482-a332-46226111e174</wsa:MessageID>
     7     <wsa:ReplyTo>
     8       <wsa:Address>http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</wsa:Address>
     9     </wsa:ReplyTo>
    10     <wsa:From>
    11       <wsa:Address>urn:uuid:ba7cf5a6-a324-4b3e-bd51-48b34dba6d76</wsa:Address>
    12     </wsa:From>
    13     <UNS1:ServiceIdentifier>uri:prn</UNS1:ServiceIdentifier>
    14   </soap:Header>
    15   <soap:Body>
    16     <pri:GetPrinterElementsRequest>
    17       <pri:RequestedElements>
    18         <pri:Name>pri:PrinterDescription</pri:Name>
    19         <pri:Name>pri:PrinterConfiguration</pri:Name>
    20         <pri:Name>pri:PrinterCapabilities</pri:Name>
    21         <pri:Name>pri:DefaultPrintTicket</pri:Name>
    22         <pri:Name>pri:PrinterStatus</pri:Name>
    23       </pri:RequestedElements>
    24     </pri:GetPrinterElementsRequest>
    25   </soap:Body>
    26 </soap:Envelope>
  

     1 <?xml version="1.0"?>
     2 <SOAP-ENV:Envelope xmlns:SOAP-ENV="http://www.w3.org/2003/05/soap-envelope" xmlns:SOAP-ENC="http://www.w3.org/2003/05/soap-encoding" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:UNS1="http://www.microsoft.com/windows/test/testdevice/11/2005" xmlns:c14n="http://www.w3.org/2001/10/xml-exc-c14n#" xmlns:wsdp="http://schemas.xmlsoap.org/ws/2006/02/devprof" xmlns:lxk1="urn:lxk_ws_demo" xmlns:wse="http://schemas.xmlsoap.org/ws/2004/08/eventing" xmlns:xop="http://www.w3.org/2004/08/xop/include" xmlns:wsa="http://schemas.xmlsoap.org/ws/2004/08/addressing" xmlns:wprt="http://schemas.microsoft.com/windows/2006/08/wdp/print">
     3   <SOAP-ENV:Header>
     4     <wsa:MessageID SOAP-ENV:mustUnderstand="true">uuid:3de53c9e-1694-49ac-a66c-33e6f32e65e6</wsa:MessageID>
     5     <wsa:RelatesTo SOAP-ENV:mustUnderstand="true">urn:uuid:a74b1759-ac13-4482-a332-46226111e174</wsa:RelatesTo>
     6     <wsa:To SOAP-ENV:mustUnderstand="true">http://schemas.xmlsoap.org/ws/2004/08/addressing/role/anonymous</wsa:To>
     7     <wsa:Action SOAP-ENV:mustUnderstand="true">http://schemas.microsoft.com/windows/2006/08/wdp/print/GetPrinterElementsResponse</wsa:Action>
     8     <UNS1:ServiceIdentifier SOAP-ENV:mustUnderstand="true">uri:prn</UNS1:ServiceIdentifier>
     9   </SOAP-ENV:Header>
    10   <SOAP-ENV:Body>
    11     <wprt:GetPrinterElementsResponse>
    12       <wprt:PrinterElements>
    13         <wprt:ElementData Valid="true" Name="wprt:PrinterDescription">
    14           <wprt:PrinterDescription>
    15             <wprt:ColorSupported>false</wprt:ColorSupported>
    16             <wprt:DeviceId>MANUFACTURER:Dell;COMMAND SET:PCL 6 Emulation, PostScript Level 3 Emulation, NPAP, PJL;MODEL:Dell 2330dn Laser Printer;CLS:PRINTER;DES:Dell 2330dn Laser Printer;CID:;COMMENT:ECP1.0, LV_043D, LP_5231, LF_0056;</wprt:DeviceId>
    17             <wprt:MultipleDocumentJobsSupported>false</wprt:MultipleDocumentJobsSupported>
    18             <wprt:PagesPerMinute>35</wprt:PagesPerMinute>
    19             <wprt:PrinterName xml:lang="en">dell2330</wprt:PrinterName>
    20             <wprt:PrinterInfo xml:lang="en">DefContact and DefLocation</wprt:PrinterInfo>
    21             <wprt:PrinterLocation xml:lang="en">DefLocation</wprt:PrinterLocation>
    22           </wprt:PrinterDescription>
    23         </wprt:ElementData>
    24         <wprt:ElementData Valid="true" Name="wprt:PrinterConfiguration">
    25           <wprt:PrinterConfiguration>
    26             <wprt:PrinterEventRate>1</wprt:PrinterEventRate>
    27             <wprt:Storage>
    28               <wprt:StorageEntry Name="RAM">
    29                 <wprt:Type>RAM</wprt:Type>
    30                 <wprt:Size>33554432</wprt:Size>
    31                 <wprt:Free>-1</wprt:Free>
    32               </wprt:StorageEntry>
    33             </wprt:Storage>
    34             <wprt:Consumables>
    35               <wprt:ConsumableEntry Name="Black Toner">
    36                 <wprt:Type>Toner</wprt:Type>
    37                 <wprt:Color>Black</wprt:Color>
    38                 <wprt:Level>90</wprt:Level>
    39               </wprt:ConsumableEntry>
    40               <wprt:ConsumableEntry Name="Fuser">
    41                 <wprt:Type>Fuser</wprt:Type>
    42                 <wprt:Color>Other</wprt:Color>
    43                 <wprt:Level>93</wprt:Level>
    44               </wprt:ConsumableEntry>
    45               <wprt:ConsumableEntry Name="Photo Drum">
    46                 <wprt:Type>PC-Drum</wprt:Type>
    47                 <wprt:Color>Black</wprt:Color>
    48                 <wprt:Level>70</wprt:Level>
    49               </wprt:ConsumableEntry>
    50             </wprt:Consumables>
    51             <wprt:InputBins>
    52               <wprt:InputBinEntry Name="Tray 1">
    53                 <wprt:FeedDirection>LongEdgeFirst</wprt:FeedDirection>
    54                 <wprt:MediaSize>iso_a4_210x297mm</wprt:MediaSize>
    55                 <wprt:MediaType>other</wprt:MediaType>
    56                 <wprt:Capacity>250</wprt:Capacity>
    57                 <wprt:Level>-1</wprt:Level>
    58               </wprt:InputBinEntry>
    59               <wprt:InputBinEntry Name="MP Tray">
    60                 <wprt:FeedDirection>LongEdgeFirst</wprt:FeedDirection>
    61                 <wprt:MediaSize>iso_a4_210x297mm</wprt:MediaSize>
    62                 <wprt:MediaType>other</wprt:MediaType>
    63                 <wprt:Capacity>50</wprt:Capacity>
    64                 <wprt:Level>-1</wprt:Level>
    65               </wprt:InputBinEntry>
    66               <wprt:InputBinEntry Name="Manual Paper">
    67                 <wprt:FeedDirection>LongEdgeFirst</wprt:FeedDirection>
    68                 <wprt:MediaSize>iso_a4_210x297mm</wprt:MediaSize>
    69                 <wprt:MediaType>other</wprt:MediaType>
    70                 <wprt:Capacity>-1</wprt:Capacity>
    71                 <wprt:Level>-1</wprt:Level>
    72               </wprt:InputBinEntry>
    73               <wprt:InputBinEntry Name="Manual Envelope">
    74                 <wprt:FeedDirection>LongEdgeFirst</wprt:FeedDirection>
    75                 <wprt:MediaSize>pwg_letter-or-a4_choice</wprt:MediaSize>
    76                 <wprt:MediaType>envelope</wprt:MediaType>
    77                 <wprt:Capacity>-1</wprt:Capacity>
    78                 <wprt:Level>-1</wprt:Level>
    79               </wprt:InputBinEntry>
    80             </wprt:InputBins>
    81             <wprt:Finishings>
    82               <wprt:CollationSupported>true</wprt:CollationSupported>
    83               <wprt:DuplexerInstalled>true</wprt:DuplexerInstalled>
    84             </wprt:Finishings>
    85             <wprt:OutputBins>
    86               <wprt:OutputBinEntry Name="Standard Bin">
    87                 <wprt:Capacity>150</wprt:Capacity>
    88                 <wprt:Level>-1</wprt:Level>
    89               </wprt:OutputBinEntry>
    90             </wprt:OutputBins>
    91           </wprt:PrinterConfiguration>
    92         </wprt:ElementData>
    93         <wprt:ElementData Valid="true" Name="wprt:PrinterCapabilities">
    94           <wprt:PrinterCapabilities>
    95             <wprt:JobValues>
    96               <wprt:JobProcessing>
    97                 <wprt:Copies>
    98                   <wprt:MaxValue>999</wprt:MaxValue>
    99                 </wprt:Copies>
   100                 <wprt:Priority>
   101                   <wprt:MaxValue>50</wprt:MaxValue>
   102                 </wprt:Priority>
   103               </wprt:JobProcessing>
   104               <wprt:DocumentProcessing>
   105                 <wprt:MediaSizeName>
   106                   <wprt:AllowedValue>na_letter_8.5x11in</wprt:AllowedValue>
   107                 </wprt:MediaSizeName>
   108                 <wprt:MediaType>
   109                   <wprt:AllowedValue>unknown</wprt:AllowedValue>
   110                 </wprt:MediaType>
   111                 <wprt:MediaColor>
   112                   <wprt:AllowedValue>unknown</wprt:AllowedValue>
   113                 </wprt:MediaColor>
   114                 <wprt:NumberUp>
   115                   <wprt:PagesPerSheet>
   116                     <wprt:AllowedValue>1</wprt:AllowedValue>
   117                   </wprt:PagesPerSheet>
   118                   <wprt:Direction>
   119                     <wprt:AllowedValue>RightDown</wprt:AllowedValue>
   120                   </wprt:Direction>
   121                 </wprt:NumberUp>
   122                 <wprt:Orientation>
   123                   <wprt:AllowedValue>Portrait</wprt:AllowedValue>
   124                 </wprt:Orientation>
   125                 <wprt:Resolution>
   126                   <wprt:AllowedValue>
   127                     <wprt:Width>1200</wprt:Width>
   128                   </wprt:AllowedValue>
   129                 </wprt:Resolution>
   130                 <wprt:PrintQuality>
   131                   <wprt:AllowedValue>Normal</wprt:AllowedValue>
   132                 </wprt:PrintQuality>
   133                 <wprt:Sides>
   134                   <wprt:AllowedValue>OneSided</wprt:AllowedValue>
   135                 </wprt:Sides>
   136               </wprt:DocumentProcessing>
   137             </wprt:JobValues>
   138             <wprt:DocumentValues>
   139               <wprt:DocumentDescription>
   140                 <wprt:Compression>
   141                   <wprt:AllowedValue>gzip</wprt:AllowedValue>
   142                 </wprt:Compression>
   143                 <wprt:Format>
   144                   <wprt:AllowedValue>application/octet-stream</wprt:AllowedValue>
   145                 </wprt:Format>
   146               </wprt:DocumentDescription>
   147             </wprt:DocumentValues>
   148           </wprt:PrinterCapabilities>
   149         </wprt:ElementData>
   150         <wprt:ElementData Valid="true" Name="wprt:DefaultPrintTicket">
   151           <wprt:DefaultPrintTicket>
   152             <wprt:JobDescription>
   153               <wprt:JobName>Default job</wprt:JobName>
   154               <wprt:JobOriginatingUserName>Unknown</wprt:JobOriginatingUserName>
   155             </wprt:JobDescription>
   156           </wprt:DefaultPrintTicket>
   157         </wprt:ElementData>
   158         <wprt:ElementData Valid="true" Name="wprt:PrinterStatus">
   159           <wprt:PrinterStatus>
   160             <wprt:PrinterCurrentTime>1970-01-01T00:00:32Z</wprt:PrinterCurrentTime>
   161             <wprt:PrinterState>Idle</wprt:PrinterState>
   162             <wprt:QueuedJobCount>0</wprt:QueuedJobCount>
   163           </wprt:PrinterStatus>
   164         </wprt:ElementData>
   165       </wprt:PrinterElements>
   166     </wprt:GetPrinterElementsResponse>
   167   </SOAP-ENV:Body>
   168 </SOAP-ENV:Envelope>
  

If you squint, you can just about make out the IEE 1284 Device ID string in the DeviceId element (line 16).

I think that's enough XML for today.

In theory a CUPS backend could be written to discover and print to printers using WS-Print. In practice there's no point since the printers probably all implement IPP anyway.

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