使用SharpPCap在C#下进行网络抓包

在做大学最后的毕业设计了,无线局域网络远程安全监控策略
那么抓包是这个系统设计的基础
以前一直都是知道用winpcap的,现在网上搜了一下,有用C#封装好了的,很好用
下面是其中的几个用法
这个类库作者的主页:http://www.tamirgal.com/home/default.aspx

PcapOpen()有下面几个方法

• PcapOpen()
• PcapOpen(bool promiscuous_mode)
• PcapOpen(bool promiscuous_mode, int read_timeout)

promiscuous_mode:在普通的抓取模式下,我们只抓取那些目的地为目标网络的包,而处于promiscuous_mode时,则抓取所有的包,包括转发的包.通常我们都是开启这种模式的

下面是示例:

//Extract a device from the list

PcapDevice device = devices[i];

//Register our handler function to the 

//‘packet arrival‘ event

device.PcapOnPacketArrival += 

  new SharpPcap.PacketArrivalEvent(device_PcapOnPacketArrival);

//Open the device for capturing

 //true -- means promiscuous mode

//1000 -- means a read wait of 1000ms

device.PcapOpen(true, 1000);

Console.WriteLine(

    "-- Listenning on {0}, hit ‘Enter‘ to stop...",

    device.PcapDescription);

//Start the capturing process

device.PcapStartCapture();

//Wait for ‘Enter‘ from the user.

Console.ReadLine();

//Stop the capturing process

device.PcapStopCapture();

//Close the pcap device
device.PcapClose();

PcapStartCapture()对应PcapStopCapture()

使用PcapCapture(int packetCount)时我们可以使用SharpPcap.INFINITE,来达到持续抓包的功能

Note:通常CRC的数据是不在数据包的中的,因为通常错误的CRC包会被自动丢弃.

上面的需要注册一个event handle,这在很多时候是不可行的,所以我们推荐使用下面这个方法PcapGetNextPacket()

//Extract a device from the list

PcapDevice device = devices[i];

//Open the device for capturing
//true -- means promiscuous mode
//1000 -- means a read wait of 1000ms
device.PcapOpen(true, 1000);
Console.WriteLine();
Console.WriteLine("-- Listenning on {0}...",
device.PcapDescription);
Packet packet = null;

//Keep capture packets using PcapGetNextPacket()
while( (packet=device.PcapGetNextPacket()) != null )

{

    // Prints the time and length of each received packet

    DateTime time = packet.PcapHeader.Date;

    int len = packet.PcapHeader.PacketLength;

    Console.WriteLine("{0}:{1}:{2},{3} Len={4}", 

              time.Hour, time.Minute, time.Second, 

              time.Millisecond, len);

}

//Close the pcap device

device.PcapClose();

Console.WriteLine("-- Capture stopped, device closed.");

PcapSetFilter() 设置过滤条件

string filter = "ip and tcp";

device.PcapSetFilter( filter );

下面这个例子通过抓取TCP包,输出他们的时间,长度,源IP,源端口,目的IP,目的端口

/// <SUMMARY>

/// Prints the time, length, src ip, 

/// src port, dst ip and dst port

/// for each TCP/IP packet received on the network

/// </SUMMARY>

private static void device_PcapOnPacketArrival(
                       object sender, Packet packet)

{            

    if(packet is TCPPacket)

    {                

        DateTime time = packet.Timeval.Date;

        int len = packet.PcapHeader.len;

        TCPPacket tcp = (TCPPacket)packet;

        string srcIp = tcp.SourceAddress;

        string dstIp = tcp.DestinationAddress;

        int srcPort = tcp.SourcePort;

        int dstPort = tcp.DestinationPort;

        Console.WriteLine("{0}:{1}:{2},

            {3} Len={4} {5}:{6} -> {7}:{8}", 

            time.Hour, time.Minute, time.Second, 

            time.Millisecond, len, srcIp, srcPort, 

            dstIp, dstPort);

    }

 }