The UPnP Media Renderer
UPnP Media Renderer's structure and behaviour
Addressing
The first thing to do is to join a network. The device usually obtains an IP address via DHCP.
SSDP section
This part is responsible of the device discovery through the SSDP protocol which uses the UDP transport protocol on port 1900. When the Media Renderer starts, it automatically announces itself to the UPnP network through an SSDP Notify message with ssdp:alive. When the Control Point sends an SSDP Search message, the device sends an SSDP Search Response message. SSDP Notify and Search messages are multicast (HTTPMU), instead SSDP Search Response messages are unicast (HTTPU). Here below and in the next page we can see respectively a pretty-print of an SSDP search request performed by the Control Point and the corresponding response sent by the device.
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Incoming SSDP search request:
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M-SEARCH * HTTP/1.1
User-Agent: uhttp/0.6 libuhttp++/0.6
Accept: */*
ST: upnp:rootdevice
MX: 3
MAN: "ssdp:discover"
HOST: 239.255.255.250:1900
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