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ssdp_support.md

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UPnP/SSDP Support

UPnP/SSDP Support in Physical Web addresses the same use cases as for mDNS Support, but uses a different protocol to advertise and receive URLs. There are different options to support UPnP or SSDP in Physical Web as described in the subsections below. The current Android implementation supports the SSDP Only option (please refer to the Discussion section for more details about this decision). The Physical Web Advertiser is a cross platform command line tool based on Node.js that can be used to advertise URLs over SSDP. The new Physical Web Chrome App supports also SSDP.

SSDP support for iOS is work in progress

SSDP Only

  • Ideas

    • define new device type for Physical Web devices e.g. urn:physical-web-org:device:Basic:1
    • Use LOCATION property in SSDP messages to advertise the URL of the web page instead of URL of the XML device description
    • Search targets properties NT or ST are always urn:physical-web-org:device:Basic:1

  • New Physical Web device appears in the network

    NOTIFY * HTTP/1.1
HOST: 239.255.255.250:1900
CACHE-CONTROL: max-age = seconds until advertisement expires
LOCATION: URL of the web page to advertise
NT: urn:physical-web-org:device:Basic:1
NTS: ssdp:alive
SERVER: OS/version UPnP/1.0 product/version
USN: advertisement UUID

  • Physical Web device disappears from the network

    NOTIFY * HTTP/1.1
HOST: 239.255.255.250:1900
NT: urn:physical-web-org:device:Basic:1
NTS: ssdp:byebye
USN: uuid:advertisement UUID

  • Physical Web Browser searches for Physical Web devices in the network

    M-SEARCH * HTTP/1.1
HOST: 239.255.255.250:1900
MAN: "ssdp:discover"
MX: seconds to delay response
ST: urn:physical-web-org:device:Basic:1

  • Physical Web device responds to search request

    HTTP/1.1 200 OK
CACHE-CONTROL: max-age = seconds until advertisement expires
DATE: when response was generated
EXT:
LOCATION: URL of the web page to advertise
SERVER: OS/version UPnP/1.0 product/version
ST: urn:physical-web-org:device:Basic:1
USN: advertisement UUID

UPnP Basic Device

  • Ideas

    • Use UPnP Basic Device Profile. <deviceType> is urn:schemas-upnp-org:device:Basic:1
    • Use <presentationURL> element of the XML device description for the URL of the web page to advertise. If <presentationURL> element is not set, device will be ignored
    • Additionaly the <friendlyName> and <icon><url> elements of the device description can be used for title and icon location

  • UPnP Device Description

    <?xml version="1.0"?>
<root xmlns="urn:schemas-upnp-org:device-1-0">
	<specVersion>
		<major>1</major>
		<minor>0</minor>
	</specVersion>
	<URLBase>base URL for all relative URLs</URLBase>
	<device>
		<deviceType>urn:schemas-upnp-org:device:Basic:1</deviceType>
		<!-- The friendlyName element is the best place to put 
		     the title to display in the Physical Web Browser -->
		<friendlyName>short user-friendly title</friendlyName>
		<manufacturer>manufacturer name</manufacturer>
		<manufacturerURL>URL to manufacturer site</manufacturerURL>
		<modelDescription>long user-friendly title</modelDescription>
		<modelName>model name</modelName>
		<modelNumber>model number</modelNumber>
		<modelURL>URL to model site</modelURL>
		<serialNumber>manufacturer's serial number</serialNumber>
		<UDN>uuid:UUID</UDN>
		<UPC>Universal Product Code</UPC>
		<iconList>
			<icon> 
				<mimetype>image/format</mimetype>
				<width>horizontal pixels</width>
				<height>vertical pixels</height>
				<depth>color depth</depth>
				<!-- The icon -> url element is the best place 
				     to put the location of the icon to display 
				     in the Physical Web Browser -->
				<url>URL to icon</url>
			</icon>
		</iconList>
		<!-- The presentationURL element is the best place to 
		     put the URL to broadcast -->
		<presentationURL>URL for presentation</presentationURL>
	</device>
</root>

Any UPnP Device with <presentationUrl>

  • Ideas
    • Same usage as for UPnP Basic device but consider all UPnP devices in the network that have a <presentationURL> element. If <presentationURL> element is not set, device will be ignored
    • Use upnp:rootdevice to search for all UPnP devices in the network
    • UPnP Basic Devices will be also considered since they are also UPnP root devices

Discussion

  • SSDP Only option is better in term of saving computing resources on the mobile device. The Physical Web Browser needs to send only one SSDP message that contains the search request and fetch the value of the LOCATION property from each received SSDP response message. Disadvantage is that the LOCATION property is not used as specified in SSDP for the URL of the device description XML.
  • Options UPnP Basic Device and Any UPnP Device use LOCATION property of the SSDP messages as specified in UPnP for the URL of the device description xml. This means for each found device the Physical Web Browser needs to send and additional request (HTTP GET) to get and parse the XML device description and then fetch the <presentationUrl> element