I try to access an UPnP device running on an NT4.0 machine from a linux machine. If the device runs and a client comes online I can capture the M-search request and the response from the Windows machine:
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SSDP: SSDP Request M-SEARCH method (from client using port 1190)
SSDP: SSDP Response (to client using port 1190)
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But the client on the linux machine doesn't react (the package does arrive and the client is listening on the right port)
If the client runs and the device comes online the connection becomes established without problems.