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1.引言随着Internet上信息资源的日益丰富和多样化,传统的信息获取方式已不能满足人们希望快速准确地获取信息的要求。传统的信息获取方式基于的是Client/Server模型,主要采用“Pull(拉取)”技术获取信息。在这种方式下,客户首先向职务器发出请求,然后由服务器返回客户所需的信息。这就存在着某些局限性,为了与服务器建立连接,客户必须确切地知道服务器的地址;由于信息的经常更新,使得用户需不时地访问该站点以获取最新数据。从网络的角度来看,拉取技术基于面向连接的网络协议,提供可靠的数据包传送服务(无错,有序,无丢失),这
1. Introduction With the increasingly rich and diversified information resources on the Internet, the traditional ways of obtaining information can no longer meet the requirements that people want to obtain information quickly and accurately. The traditional method of obtaining information is based on the Client / Server model, mainly using “pull” technology to obtain information. In this way, the client first makes a request to the server, and then the server returns the information the customer needs. This has some limitations, in order to establish a connection with the server, the client must know exactly the server’s address; due to frequent updates of the information, users need to visit the site from time to time to obtain the latest data. From a network perspective, pull technology is based on connection-oriented network protocols that provide reliable packet delivery (error-free, orderly, and lossless).