Netty Server communicating with android client

Quick question. I'm in the process of developing a java server/android client app. The server is nearly complete...it works using a thread-per-client approach. However this will not scale very well when dealing with many clients connecting at once. This lead me to research some server-side solutions. I came across Netty, as it seems to be what I'm looking for as far as the scalability issue is concerned. Before I get too far into finishing the server I'd like to get the core down and not have to go back later to re-design it after the fact.

Netty used to not be compatible with Android, but apparently since 3.3(ish) it has been. It is now at 4.0, however I couldn't really find any resources for learning how to implement it for an android client/ java server combo. Does anyone here have any experience in this area? If not, are there any resources that are out there which could help me to better understand and use Netty for this purpose?
If you plan to use Google App Engine you can evaluate Google Cloud Endpoints (admittedly this is a "preview release")
Else how about plain old servlets with JSON?

I had no idea about the Google App engine/Endpoints...that's really cool stuff. Perhaps I should approach the design from the android side first then figure exactly what the server needs to do.

Just FYI, I have a very rudimentary java client that I'm using to communicate/test the server with, so I have a rough idea of what the android app needs to do. When you talk about the plain servlets/JSON, would this get rid of the thread-per-connection issue? The system I'm developing will be responsible for maintaining mass connections (hundreds per server) in the same chat session.

So far it seems that the only way to avoid this is to either have the chat read/write into an SQL database (which seems like it would be ineffecient and slow) or implement some java NIO server functions (which apparently don't work well with the Android API).

Now I understand.
100s/1000s might have logged in to the group chat, but how many are posting at the same time? Hardly a few.
You will just need to notify all other 999 clients that client 1 said "Howdy" Check out Google cloud messaging