收发ICMP封包，实现ping

#include "stdafx.h"

#include <WINSOCK2.H>
#pragma comment(lib, "Ws2_32.lib")

#define ECHO_REPLY   0  //回应
#define ECHO_REQUEST 8  //请求回应

struct ip_hdr
{
    unsigned char h_len:4;         //length of header
    unsigned char version:4;       //Version of IP
    unsigned char tos;             //Type of service
    unsigned short total_len;      //total length of the packet
    
    unsigned short ident;          //unique identifier
    unsigned short frag_and_flags; //flags
    
    unsigned char ttl;             //ttl
    unsigned char proto;           //protocol(TCP ,UDP etc)
    unsigned short checksum;       //IP checksum
    
    unsigned int sourceIP;
    unsigned int destIP;
};

struct icmp_hdr 
{
    BYTE icmp_type;     //类型
    BYTE icmp_code;     //代码
    USHORT icmp_cksum;  //效验和
    USHORT icmp_id;     //n
    USHORT icmp_seq;    //n
    ULONG  icmp_data;   //GetTickout()
};

//计算ICMP封包校验和
WORD CalcCheckSum(IN unsigned short* addr,IN int len)
{
    int        nleft = len;
    int        sum = 0;
    unsigned short* w = addr;
    unsigned short answer = 0;
    
    while(nleft > 1) 
    {
        sum += *w++;
        nleft -= 2;
    }
    
    if(nleft == 1) 
    {
        *(unsigned char*)(&answer) = *(unsigned char*)w;
        sum += answer;
    }
    
    sum = (sum >> 16) + (sum & 0xffff); //高16位 + 低16位
    sum += (sum >> 16);                 //+进位
    answer = ~sum;                      //取反
    
    return (answer);
}

int main(int argc, char* argv[])
{
    //socket初始化
    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 2), &wsaData);

    //没有域名，返回
    if (argc < 2)
    {
        puts("Get Domain Error");
        return 0;
    }

    //域名转IP地址
    HOSTENT *pHost = gethostbyname(argv[1]);
    if (pHost == NULL)
    {
        puts("Get Domain Error");
        return 0;
    }

    unsigned long nAddress = ((long**)pHost->h_addr_list)[0][0];
    sockaddr_in addrSend;
    addrSend.sin_family = AF_INET;
    addrSend.sin_port = htons(0);
    addrSend.sin_addr.s_addr = nAddress;
    
    //创建原始套接字
    SOCKET sRaw = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
    if (sRaw == INVALID_SOCKET)
    {
        puts("socket error");
        return 0;
    }

    printf("Pinging [ %s ] with 32 bytes of data:

", argv[1]);

    char szSend[32] = {0};
    for (int i = 0; i < 4; i++)
    {
        icmp_hdr *pICMP = (icmp_hdr *)szSend;
        pICMP->icmp_code = 0;
        pICMP->icmp_cksum = 0;
        pICMP->icmp_data = ::GetTickCount();
        pICMP->icmp_id = (unsigned short)GetCurrentProcessId();
        pICMP->icmp_seq = i;
        pICMP->icmp_type = ECHO_REQUEST;

        pICMP->icmp_cksum = CalcCheckSum((unsigned short *)pICMP, sizeof(icmp_hdr));

        //发送封包
        sendto(sRaw, szSend, sizeof(szSend), 0, (sockaddr *)&addrSend, sizeof(addrSend));

        //通过选择模型，设置等待时间
        fd_set fd;
        FD_ZERO(&fd);
        FD_SET(sRaw, &fd);
        timeval tv = {1, 0};
        int nResult = select(0, &fd, NULL, NULL, &tv);
        if (nResult == 0)
        {
            puts("Time Out");
            continue;
        }

        //接收封包
        char szRecv[MAXBYTE];
        sockaddr_in addrRecv;
        int nLen = sizeof(addrRecv);
        recvfrom(sRaw, szRecv, sizeof(szRecv), 0, (sockaddr *)&addrRecv, &nLen);

        //检验校验和
        ip_hdr * pIPRecv = (ip_hdr *)szRecv;
        icmp_hdr *pICMPRecv = (icmp_hdr *)(pIPRecv + 1);

        //校验和为0，表示封包正确
        if (!CalcCheckSum((unsigned short *)pICMPRecv, sizeof(icmp_hdr)))
        {
            //计算时间间隔
            DWORD dwTime = ::GetTickCount() - pICMPRecv->icmp_data;
            
            printf("Reply from %s: bytes=%d time=%dms TTL=%d
", 
                inet_ntoa(addrRecv.sin_addr), 
                sizeof(szRecv), 
                dwTime, 
                pIPRecv->ttl);
        }
    }


    //格式控制
    puts("");

    //socket释放资源
    WSACleanup( );
    return 0;
}