摘要网络嗅探器是利用网络设备接口截获网络中传输信息的一种工具，传统的网络嗅探器一般是基于有线网络环境下，利用以太网卡的混杂模式来实现嗅探功能。而在无线网络迅速普及的今天，无线网络中的数据信息越来越被人们所重视，本课题是就是在这个背景下设计一款小型网络嗅探器，捕获无线局域网中的数据信息，完成一定范围内的移动设备数量的监测。86790

本课题的开发环境为树莓派，即基于Linux平台，利用网卡的RFMON模式，使用C语言完成功能设计。在具体设计中，利用Libpcap这一强大的数据包捕获函数库编写监听网络接口和捕捉网络中数据信息的程序。通过对无线局域网中的不同数据帧格式的分析，定义并解析物理层硬件设备信息和数据帧头部信息，取出数据帧的MAC地址。

设计最终实现了无线局域网内所有数据信息的捕获和周围无线信号以及通信设备硬件标识信息的嗅探，周期性地运行程序可以监测到一定范围内的移动设备数量变化。本文最后通过测试处于实验室环境下的嗅探器，观察MAC地址的数量变化，验证了实验室人流量的变化情况。

毕业论文关键词：嗅探器；无线局域网；RFMON技术；网络抓包

Abstract Network sniffer is a tool for capturing packets transmitted information on the network through network interface。 The traditional network sniffer generally capture network data packets and realize its monitor function by using promiscuous mode of ethernet card in wired network environment。 Nowadays, with the rapid popularization of wireless network, people pay more attention to the information in WLAN。 We manage to design a small network under this background, which can capture the packets in WLAN and monitor changes in quantity of communication equipments at a certain extent。

Our hardware environment to design sniffer is raspberry pi, which is based on Linux system and we use C language to realize it through RFMON technology。 Specifically ,We design a program code to monitor network device interface and capture packets in WLAN by using Libpcap, a rich function library。 Then define and analyze the data packets as well as hardware devices information in physical layers by learning the structure of frames in WLAN。 At last, pick up the MAC address from the frame headers。

This project finally implement functions that capture all data packets in WLAN and monitor WiFi signals as well as communication devices information。 We can notice the changes of the number of communication devices by running program periodically in a certain range of area。 In the last part of the paper, We observe the changes of the number of MAC addresses by testing the sniffer we design in the laboratory。 The results are consistent with the changes of the number of students in the laboratory。

Key words: Sniffer; WLAN; RFMON; Packet Capture

目   录

第一章 绪论 1

1。1 历史背景 1

1。2 嗅探器在当下的应用 1

1。3 本课题的研究意义 2

1。4 本课题的研究内容 2

第二章 嗅探器的基本原理 3

2。1 嗅探器的实现基础 3

2。1。1 以太网数据帧的传输 3

2。1。2 无线局域网的运作原理 3

2。1。3 无线与有线网络数据传输的区别 5

2。2 数据包的捕获 5

2。2。1 数据包的捕获原理