以IP-Multicast為基礎之快速Java訊息傳遞機制

Abstract

網際網路的日益發達，程式之間透過網路來溝通及交換訊息或是向各種資訊提供者取得資訊也日趨頻繁。但是傳統的client/server模式卻造成用戶端程式必須要去管理及維護建立連線的系統資源。同時，使用者程式也必須採用輪詢(polling)的方式取得這些資訊，不但浪費系統資源也降低網路的使用率。而以訊息導向之中介層可讓程式開發人員能快速發展具分散性、可重用性、安全性，事件驅動之網路應用程式。 本研究提出了一個以訊息為導向之中介層系統，稱之為 FJM (Fast Java Messaging)。FJM 完全以 Java 實作，提供了 Java Messaging Service (JMS) 的 發送/訂閱應用程式界面。為了減少訊息傳送的額外負擔，如連線的數目和控制封包的數量，FJM 建構於以 IP-multicast 為基礎的群組通訊協定之上。在本研究裡，我們將會討論 FJM 的架構，所使用的群組通訊協定、以及 FJM 在實作上的問題，例如 Topic 名字 與 IP-Multicast 位址之間的對應方式、執行緒模型、緩衝區管理……等。本研究的經驗，可供想使用 Java 和 群組通訊協定，來開發網路通訊中介層的讀者作為參考。

With the growth of Internet, the communication, message exchange, and obtaining information from information provider through the network is increasingly frequent. However, the conventional client/server model causes user programs have to manage and maintain the system resources of connections. In the meantime, user programs obtain the information by polling servers. It not only consumes system resources but also reduces the network utilization. Therefore, message oriented middleware is proposed and it lets programmers develop distributed, reusable, secure, and event- driven network applications rapidly. This research proposed a Message Oriented Middleware, named FJM (Fast Java Messaging). FJM is a Java Message Service implemented in the pure Java programming language. FJM is built onto the IP Multicast-based group communication protocol in order to reduce the overhead of message transmission such as the number of connections and control packets. In this thesis, we will describe the FJM architecture, group communication protocol in FJM, and implementation issues in detail, such as topic-address mapping, thread model, buffer management etc., in detail. The experiences in this thesis also can be a good reference, which help to create network-based middleware using Java and group communication protocol.