Are you running Gnome 3? If so, then vnc4server and vnctightserver do not support your use case and xrdp is relying on one of them to do so. Either revert to an older desktop environment (something like Gnome 2, I'm not really sure) or have xrdp use a vnc server that does support Gnome 3, like vino.
Today, I have been trying to get xrdp working on my Debian Jessie install. I have not tried reverting to an older desktop environment, but I have at least got a connection through xrdp using vino as the vncserver. I have not stress tested this though.
Of course, if you use vino, then you need to resolve the issue of vino's encryption not being supported by xrdp (or by a VNC viewer you might use to test vino). This is doable, but the solution is to turn off vino's encryption unfortunately. I'm fairly sure this won't matter if you run xrdp and vino on the same machine (traffic to/from vino goes through 127.0.0.1 in this case, and nowhere else on the network), but I'm not an expert on this and have not verified that xrdp's encyption is doing its job when vino's is turned off (xrdp's encryption could protect traffic between your RDP client and xrdp).
Also, for testing basic connectivity, I recommend having an RDP client and a VNC viewer installed on the machine you are setting xrdp up on. xfreerdp and Gnome's default VNC client (Vinagre, aka Remote Desktop Viewer) worked for me and simplified testing a lot. Get VNC working first, then move on to getting RDP working. Beware, Vinagre will not help you verify the vino encryption issue since Vinagre actually supports vino's encryption format.
Finally, for testing remote connectivity from an Android device, I was able to use
aFreeRDP and
VNC Viewer. With aFreeRDP, the last hurdle I had to resolve was that I had to specify exactly the same resolution as was present in the running session on my host. But since I had already gotten a connection with xfreerdp locally, this was a lot easier to approach since I knew RDP should work now, I just had to figure out if the firewalls (firewalls were the penultimate hurdle) or the client's config were the issues.
If you are using Gnome 3 on Debian Jessie, then you may find
this stackoverflow answer useful for figuring out why xrdp (and actually VNC) is not working out of the box. Here's the
debian bug report.
You may find
this wiki article to be useful setting up xrdp to use vino.
You may find this
stackoverflow answer to be informative about the vino encryption issue.
Good luck, I hope this helps.