Discovery and Description (Windows CE 5.0)
Discovery is the process of a device announcing itself and finding devices through Universal Plug and Play (UPnP). This is done through Simple Service Discovery Protocol (SSDP). Every network device must host a device description document so that other devices can examine it and determine properties, supported media types, and support for Windows Media DRM 10 for Network Devices,
Discovery
Your device will use the Media Query Engine to detect UPnP Media Servers such as Windows Media Connect.
Windows Media® Connect uses standard UPnP discovery mechanisms for announcing itself and finding devices, depending on whether or not devices are Media Renderers or Control Points. Networked Media Device (NMD) are considered Control Points.
Windows Media Connect announces itself as a UPnP Media Server device using the SSDP protocol in accordance with the UPnP specification. Windows Media Connect sends out SSDP NOTIFY messages every 15 minutes. Each message is sent twice. Sample NOTIFY messages are shown below. Certain fields in these messages will have different values depending on the computer hosting Windows Media Connect.
NOTIFY * HTTP/1.1\r\n
Host:239.255.255.250:1900\r\n
NT:urn:schemas-upnp-org:service:ConnectionManager:1\r\n
NTS:ssdp:alive\r\n
Location:http://192.168.1.100:2869/upnphost/udhisapi.dll?content=uuid:224e2bb9-6961-4d79-b05f-f72cb415dc6c\r\ns
USN:uuid:224e2bb9-6961-4d79-b05f-f72cb415dc6c::urn:schemas-upnp-org:service:ConnectionManager:1\r\n
Cache-Control:max-age=1800\r\n
Server:Microsoft-Windows-NT/5.1 UPnP/1.0 UPnP-Device-Host/1.0\r\n
\r\n
NOTIFY * HTTP/1.1\r\n
Host:239.255.255.250:1900\r\n
NT:urn:schemas-upnp-org:service:ContentDirectory:1\r\n
NTS:ssdp:alive\r\n Location:http://192.168.1.100:2869/upnphost/udhisapi.dll?content=uuid:224e2bb9-6961-4d79-b05f-f72cb415dc6c\r\n
USN:uuid:224e2bb9-6961-4d79-b05f-f72cb415dc6c::urn:schemas-upnp-org:service:ContentDirectory:1\r\n
Cache-Control:max-age=1800\r\n
Server:Microsoft-Windows-NT/5.1 UPnP/1.0 UPnP-Device-Host/1.0\r\n
\r\n
NOTIFY * HTTP/1.1\r\n
Host:239.255.255.250:1900\r\n
NT:urn:schemas-upnp-org:device:MediaServer:1\r\n
NTS:ssdp:alive\r\n
Location:http://192.168.1.100:2869/upnphost/udhisapi.dll?content=uuid:224e2bb9-6961-4d79-b05f-f72cb415dc6c\r\n
USN:uuid:224e2bb9-6961-4d79-b05f-f72cb415dc6c::urn:schemas-upnp-org:device:MediaServer:1\r\n
Cache-Control:max-age=1800\r\n
Server:Microsoft-Windows-NT/5.1 UPnP/1.0 UPnP-Device-Host/1.0\r\n
\r\n
NOTIFY * HTTP/1.1\r\n
Host:239.255.255.250:1900\r\n
NT:upnp:rootdevice\r\n
NTS:ssdp:alive\r\n
Location:http://192.168.1.100:2869/upnphost/udhisapi.dll?content=uuid:224e2bb9-6961-4d79-b05f-f72cb415dc6c\r\n
USN:uuid:224e2bb9-6961-4d79-b05f-f72cb415dc6c::upnp:rootdevice\r\n
Cache-Control:max-age=1800\r\n
Server:Microsoft-Windows-NT/5.1 UPnP/1.0 UPnP-Device-Host/1.0\r\n
Windows Media Connect will also respond to any properly formatted M-SEARCH action looking for a media server. The following example shows a UPnP SEARCH message response.
M-SEARCH * HTTP/1.1\r\n
Host:239.255.255.250:1900\r\n
ST:urn:schemas-upnp-org:device:MediaServer:1\r\n
Man:"ssdp:discover"\r\n
MX:3\r\n
\r\n
Windows Media Connect Device Discovery
Windows Media Connect attempts to discover all compatible devices. This includes Media Renderers and Control Points such as the networked media device. Whenever a new network device is discovered, a balloon tip in the Windows UI will notify the user.
Control Points are discovered through UPnP actions. When a UPnP action from a Control Point comes in, the Message Authentication Code (MAC) address is checked against a stored list. If the MAC address is new, the device is announced as a new device.
The Description Document
Windows Media Connect will display information about the device if the device makes the information available. Media Renderers will be displayed with a generic name "DeviceN", where N is an integer.
Most of the device information displayed in the UI is acquired from the description document. Description documents MUST have an XML version tag (as shown here) or they will not be discovered:
<XML version = 1.0>
Devices must also host their own description document. Devices that have a description document hosted elsewhere will not be discovered.
Icons
Windows Media Connect expects icons to be 48 x 48 pixels with a color depth of 24 bits. Icons can be in the following formats:
- ICO
- BMP
- GIF
- JPEG
- PNG
- TIFF
If a 48 x 48 pixel icon is unavailable, the one that is the closest match is used, but they might not display properly. Because of this, 48 x 48 icons are recommended.
The URL pointing to the icon must be the same host as the device URL host.
Devices with no icon are represented by a generic device icon.
DRM
A custom tag has been added to identify devices that support Windows Media DRM 10 for Network Devices. If a device supports Windows Media DRM 10 for Network Devices, it must include the following XML in the device description document:
<?xml version="1.0"?>
<root xmlns="urn:schemas-upnp-org:device-1-0" xmlns:ms=" urn:microsoft-com:wmc-1-0">
<specVersion>
<major>1</major>
<minor>0</minor>
</specVersion>
<device ms:X_MS_SupportsWMDRM="true">
...
</device>
</root>
See Also
Media Query Engine Architecture
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