PDA系统通信协议研究与实现

【作者】 曹清；

【导师】 史浩山；

【作者基本信息】 西北工业大学 ， 通信与信息系统， 2004， 硕士

【摘要】 本论文结合一个PDA项目的开发，设计和实现了利用固定电话网进行信息传输的一套通信协议。 基于通信协议开发的一般过程——协议工程，同时针对于本项目的特点，本文首先分析了协议工程的缺陷，对协议工程的各项活动提出了适当的修改和裁减建议。 文章重点探讨了，如何依据修改的协议工程活动来指导通信协议的开发：在体系结构上，应用并描述C/S模式的网络架构，及其相比于交叉式的网络构架的优势所在。对比ISO七层模型，设计了简单实用的三层网络模型(物理层，链路层，消息层)。在通用的时序图描述通信协议动态交互的基础上，用一种形式化描述技术——Petri网抽象通信协议的动态行为规范为一种链路层半双工停止-等待协议，从简单到复杂建立4个不同侧重点的Petri网模型，分别描述通信协议的不同动态行为：交互，超时，出错处理。提出了对于Petri网通信模型的信道约束条件公式：∑m_t≤1。利用Petri网理论对协议进行一致性验证，并修正验证时所发现的错误。在协议实现上，为了降低实现的复杂度，提高系统性能将通信模块嵌入到窗口系统的事件循环，而不采用传统的双进程模式(应用程序与通信模块各存在于一个单独进程)。构建了基于已有测试集的本地测试和远程测试框架，分别完成对协议静态格式和动态行为的测试，并通过实际情况下的测试结果来分析一致性验证中所发现的问题。 最后，基于通信协议的安全性进行讨论。 依据完整的解决方案，我们在嵌入式Linux平台下的开发环境上，利用多种技术手段，很好的完成了整个项目，实现了整套通信协议，最终使得软件较好地达到了用户的需求。更多还原

【Abstract】 This paper laid a strong emphasis on the project how to realize the PDA’s communication with distance server.Based on the process, protocol engineer to develop the communication protocols, the paper modify and delete some activities of protocol engineering in order to be accustomed to the project.The paper enhanced how to develop the communication system of this project under the modified protocol engineer. In architecture, it expounded the C/S pattern of network architecture and pointed out the merits between C/S pattern and distribution pattern. And we designed simple and useful 3 layers network model (physical, data link, and message layer) instead of ISO. The paper not only used the sequence diagrams to descript the cooperation of PDA and server in communications, but only adopt Petri net, a kind of FDT, to built four different models on protocol’s dynamic actions. We proposed the constrict expressions: 1. Finding out and fixing theerrors, we validated the protocol with Petri net theories. We implanted communication module into message loops of windows module instead of .typical 2-processor mode. After finishing realization, we did build both local and remote testing skeleton with the set of test cases that was created in first to test static specifications and dynamic actions of protocol. And testing could help us to analyze the problems we had found in validation.At the end of the paper, we discussed something about protocol security.Based on the embedded Linux system, we study emphatically on the key technology of how to realize information mutually in the course of communicating among each module. And we find the corresponding solution. With this, we carry out the whole software successfully to meet the end user’s demands.更多还原