Communication with POS system

I want to implement a simple POS for a client because current proprietary software isnt easy to use.. PDAs(windows) connect directly to database to fetch data in current software.

For my system i believe that webservices would be an overkill. I can do a socket communication with pdas and server but this is very basic! Server would be written in java.

While searching i found that Apache Thrift is one solution but i am not sure whether server in thrift is the application...

Other solution would be using a serializer compatible java/c# but then i would have to write code for the logic.

Also i would like to be able to send notifications from server to client,otherwise i see no solution instead of using a timer..

Direct connect开发者_开发问答ion with database would result in writing twice or more the database code which doesnt seem good idea.. Also apart from databases there are other services too(printers,tax etc) Any other solution/reccomendation for this/communication?

Build RESTful APIs on the Server that your PDAs can consume.

As for server to client communication, for Android you could use the C2DM framework. This sends a notification to your Android device, and then your Android device could contact the Server. I believe iOS has a similar concept. For Windows Mobile, you could use a raw socket (client initiated connection to the server) with your own notification protocol (or build an HTTP-based one) or perhaps develop an SMS intereceptor with specially crafted messages so that the client knows to contact the server.

Using a Web Server could be a good thing. You get a few features fairly cheap, such as SSL/TLS and authentication support. Compare this to a raw sockets approach, where data gets transmitted in the clear by anybody. You'll end up building your own protocol that solves a bunch of problems HTTP already addresses.