SMILE-JS, a SIP-based middleware for J2ME devices

In this paper we report our two years experience in designing and implementing a new middleware solution for distributed mobile applications exploiting the Session Initiation Protocol (SIP) and the JavaScript Object Notation (JSON). The proposed solution has been designed to port the Simple Middleware Independent LayEr (SMILE) framework to mobile devices running the limited version of Java 2 Micro Edition (J2ME CLDC). It provides J2ME developers with the very same abstraction layer offered by the SMILE API under the J2SE environment, allowing seamless interoperability between SMILE peers running on desktop computers/servers and peers running on mobile devices. The solution will be denoted as SMILE-JS, where JS stands for JSON over SIP. We first describe the SMILE framework, explaining its APIs for communication, addressing, lifecycle management and service discovery. Afterwards we explain how truly peer to peer communication among mobile devices has been achieved using SIP, and which additions we implemented to turn the open source MjSIP framework into the first SIP-based middleware for J2ME CLDC enabled devices.