I was getting the '500' error from the client when using HTTP, and a packet capture showed HTTPS style connection attempts to the server. Perhaps Android was trying to be helpful?
Anyway, putting an HTTPS-HTTP proxy in front of the server (and specifying https:// on the client) fixed the problem.
			Anyway, putting an HTTPS-HTTP proxy in front of the server (and specifying https:// on the client) fixed the problem.
