In general, software agents deployed in a multi-agent systems (MASs) collaborate and share data with each other by means of Foundation for Intelligent Physical Agents (FIPA) communications into the same agent platform (intra-). Java Agent Development framework (JADE) provides a facility software framework to build software agents executing in a specific agent platform. This paper presents a novel agent communication gateway aimed at abstracting FIPA communication between software agents on external (inter-) platforms. The novel agent communication gateway is based on the Agent-as-a-Service model (AaaS) implemented using REST technologies. The use of this gateway can favor and enable the interoperability among agents belonging to different MASs, opening collaborations and interactions among heterogeneous agents everywhere in Internet, whenever FIPA message exchanges are used as standard. In this paper some communication paradigms are presented based on the proposed gateway. Some implementation issues show that the programming complexity of communication blocks of agents can be decreased at both Java applications and Java web systems.