[SOLVED] How can I actually download/transfer a file found using UPnP?

How can I actually download/transfer a file found using UPnP?

I'm completely new to UPnP as a protocol, but I'm hoping to use it to transfer files from a Sony Camera to an iOS app I'm working on. So far I have SSDP discovery setup, I can read the UPnP client's services, search through folders and access file names, but the final hurdle which I'm stuck on is how to actually download/transfer the files once I'm able to list them!

What I end up getting is the below:

<item id="04_02_0624600856_000001_000001_000000" restricted="1" parentID="03_01_0624600856_000001_000000_000000">
  <dc:title>DSC05076.ARW</dc:title>
  <upnp:class>object.item.imageItem.photo</upnp:class>
  <dc:date>2018-08-23T12:24:21</dc:date>
  <res protocolInfo="http-get:*:image/jpeg:DLNA.ORG_PN=JPEG_SM;DLNA.ORG_CI=1">http://192.168.122.1:60151/SM_DSC05076.ARW?%2104%5f02%5f0624600856%5f000001%5f000001%5f000000%21http%2dget%3a%2a%3aimage%2fjpeg%3aDLNA%2eORG%5fPN%3dJPEG%5fSM%3bDLNA%2eORG%5fCI%3d1%21%21%21%21%21</res>
  <res protocolInfo="http-get:*:image/jpeg:DLNA.ORG_PN=JPEG_LRG;DLNA.ORG_CI=1">http://192.168.122.1:60151/LRG_DSC05076.ARW?%2104%5f02%5f0624600856%5f000001%5f000001%5f000000%21http%2dget%3a%2a%3aimage%2fjpeg%3aDLNA%2eORG%5fPN%3dJPEG%5fLRG%3bDLNA%2eORG%5fCI%3d1%21%21%21%21%21</res>
  <res protocolInfo="http-get:*:image/jpeg:DLNA.ORG_PN=JPEG_TN;DLNA.ORG_CI=1">http://192.168.122.1:60151/TN_DSC05076.ARW?%2104%5f02%5f0624600856%5f000001%5f000001%5f000000%21http%2dget%3a%2a%3aimage%2fjpeg%3aDLNA%2eORG%5fPN%3dJPEG%5fTN%3bDLNA%2eORG%5fCI%3d1%21%21%21%21%21</res>

I would (With my naive experience of simple HTTP APIs) then expect to simply be able to download the file in question by hitting: http://192.168.122.1:60151/SM_DSC05076.ARW or similar (I'm assuming I have to change this URL slightly as the file is listed as image/jpeg rather than RAW?

Whatever combination I try of the full res object, snipping bits, decoding the url e.t.c. I always get a 404 response when trying to visit the URL in question. Is there something more complex I need to do here? Or something simple that I'm missing?

Thanks in advance!

Solution

The problem here was that I was using a url from a previous session. It turns out that the urls change between connection sessions, which is why I was getting a 404.

Lesson learned: UPnP is highly dynamic, and you can’t rely on caching images under their access MRL!