GASP: an open source gaming service middleware dedicated to multiplayer games for J2ME based mobile phones R. Pellerin+*, F. Delpiano^, F. Duclos§, E. Gressier-Soudan+, M. Simatic* pellerin@cnam.fr, fabien@infraworlds.com, fduclos@bouyguestelecom.fr, gressier@cnam.fr, michel.simatic@int-evry.fr + CNAM-CEDRIC, 292, rue St Martin, 75141 Paris Cedex 03, Tel: +33 1 58 80 85 13 France ^ InfraWorlds, 33 avenue de la République, 75011 Paris, Tel: +33 1 58 62 53 00 France § Bouygues Telecom, Centre d'affaires la Boursidière, 92355 Le plessis Robinson, Tel: +33 141 09 27 54 France * GET-INT, 9 rue Charles Fourier, 91011 Evry Cédex, Tel: +33 1 60 76 45 61. France ABSTRACT GASP is an open source platform that conforms the Open Mobile Alliance (OMA) v 1.0 specifications. It is able to handle basic services for building and handling interactions between players such as session management, communications... GASP is implemented in Java. It offers a server and a client part. It is defined for MIDP and DOJA J2ME profiles. GASP is demonstrated through Kouiz, a multiplayer game for mobiles presented in the second part of this paper. During solo phases of the game, the player tries to breed animals called kouizs. The aim is to improve their skills. With improved skills, kouizs have better chances to win against challengers in the multiplayer arena. In this mode kouizs can fight. This paper ends by discussing our current results and what we plan to do next with the gaming service platform GASP. Key Words Multiplayer games, mobile phone, GASP, OMA 1.INTRODUCTION The feasibility of multiplayer games over mobile networks is studied and tested since June 2003. First, in the context of MEGA [SIM04a][SIM04b], a project promoted and leaded by GET-INT, two aspects have been carried out. The first one was dedicated to game service middleware in a broad sense. It led to the first version of GASP, GAming Service Platform, the library described in this paper. The second aspect was related to user services acceptance and human factors. The JIMM project succeeded to MEGA. The results obtained in MEGA have been reused and extended in JIMM. JIMM offers an implementation of a multiplayer game for mobile phones and an open source middleware for gaming. JIMM is a French consortium composed of three partners. Bouygues Telecom is the leader of the project. As a mobile network provider it promotes i- mode cellular phones in the context of JIMM. It brings expertise on mobile network communications. CNAM-CEDRIC, as a research Lab on multiplayer games, is in charge of enhancing GASP. GASP is also a common research project with GET-INT. Infraworlds, as a game programming and editing company, develops a multiplayer game that benefits from GASP functionalities to handle multiplayer interactions. Kouiz is a demonstrator for GASP This paper presents our work. Section 2 is devoted to Gaming Services: the OMA proposal, a state of the art, the services implemented by GASP. Section 3 presents the game Kouiz, its goal is to illustrate the use of GASP. Section 4 states our current results, the advantages of an open source middleware, and concludes. 1.GASP, A GAMING SERVICE MIDDLEWARE Principles for networking in multiplayer games are nowadays well known [SME01]. But when trying to implement these principles in the context of mobile, game developers meet new challenges: 1) Terminals have limited capabilities (for instance, the executables cannot be more than 100-200 Kb), 2) The sending of a message has a non-negligible cost for the player, 3) http is usually the only available protocol to