In this paper, we presented an IP-multicast-based Java Message Service implementation called FJM (Fast Java Messaging) Library. We discussed its architecture, protocols, and implementation issues. For achieving better performance, we revised the original design of the FJM. The details of the refinement were also described in this paper. Then, we compared the performance of the both versions of the FJM with the performance of other JMS implementations. After our carefully design and tuning, in most cases, the revised version of the FJM can offer the highest throughput among the well-known industrial or open source JMS implementations. Therefore, FJM can be used in many innovative or mission critical cluster applications, such as massively multiplayer virtual worlds or military simulator.