* MiniSSDPd - SSDP daemon

(c) Thomas Bernard
http://miniupnp.free.fr/ or https://miniupnp.tuxfamily.org/
https://github.com/miniupnp/miniupnp/

MiniSSDPd is a daemon that :
1 - keeps track of all UPnP devices announcing themselves on the network.
its database can be queried by local processes using a protocol based on
a unix socket. That enables local processes to quickly discover UPnP devices
without broadcasting SSDP message and waiting several seconds for a response.
2 - keeps a database of local UPnP devices hosted on the machine and
answering SSDP searchs on their behalf. It enables to run several UPnP devices,
like an IGD and a MediaServer, on the same machine.

to build, use GNU Make.


* protocol :

Connect to the unix socket.
Sent request, get response.
close unix socket connection.

* Request format :
1st byte : request type
           0 - version
           1 - type
           2 - USN (unique id)
           3 - everything
           4 - submit service (see below)
           5 - switch connection to notification mode
n bytes : string length : 1 byte if < 128 else the upper bit indicate that
one additional byte should be read, etc. (see codelength.h)
n bytes = string

Response format :

request type 0 (version) :
n bytes string length
n bytes = version string

request type 1 / 2 / 3 / 5 :
1st byte : number of services/devices, from 0 to 254.
           255 is a special value, see below
For each service/device :
URL :
  n bytes string length
  n bytes = Location string
ST:
  n bytes string length
  n bytes = type string
USN:
  n bytes string length
  n bytes = identifier string

if the 1st byte is 255, the format is as follows :
1st byte = 255
2nd byte = notification type (1=NEW, 2=UPDATE, 3=REMOVE)
3rd byte = number of services/devices, from 0 to 255.


request type 4 = submit service
1st byte  = 4
(k,n) bytes : length and string "ST" (service type)
(k,n) bytes : length and string "USN"
(k,n) bytes : length and string "Server"
(k,n) bytes : length and string "Location"
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