Yes, response in most cases is just plain text, so no HTTP header or Response code.
It should be easy to fake a header and parse this on the hub side. The biggest issue is the size of the request is limited to some unknown limit (really small)
Wish we could implement some sort of S3 Image like handler so the response for the device goes up to the cloud and then we can do what we need to it from the cloud.
Raw packets (TCP only, no UDP) can be sent to devices in the device code (not smartapps) and it does work, but without a response no way to get two way info...
Very limiting in moving forward with basically any future integration... Writing a proxy / relay is the only real option.
Anyone interested in an open source, .NET windows service / HTTP proxy? I am willing to start a project and see if anyone wants to help build it out.