C++实现ping功能

今天接到需求要实现ping的功能，然后网上查了一些资料，对网络编程的一些函数熟悉了一下，虽然还有一些细节不清楚，但是慢慢积累。

要实现这样的功能：

基础知识

ping的过程是向目的IP发送一个type=8的ICMP响应请求报文，目标主机收到这个报文之后，会向源IP（发送方，我）回复一个type=0的ICMP响应应答报文。

那上面的字节、往访时间、TTL之类的信息又是从哪来的呢？这取决于IP和ICMP的头部。

IP头部：

头部内容有点多，我们关心的只有以下几个：

IHL：首部长度。因为IP的头部不是定长的，所以需要这个信息进行IP包的解析，从而找到Data字段的起始点。

　　另外注意这个IHL是以4个字节为单位的，所以首部实际长度是IHL*4字节。

Time to Live：生存时间，这个就是TTL了。

Data：这部分是IP包的数据，也就是ICMP的报文内容。

ICMP响应请求/应答报文头部：

Type：类型，type=8表示响应请求报文，type=0表示响应应答报文。

Code：代码，与type组合，表示具体的信息，参考这里。

Checksum：检验和，这个是整个ICMP报文的检验和，包括Type、Code、...、Data。

Identifier：标识符，这个一般填入本进程的标识符。

Sequence Number：序号

Data：数据部分

上面是标准的ICMP报文，一般而言，统计ping的往返时间的做法是，在ICMP报文的Data区域写入4个字节的时间戳。

在收到应答报文时，取出这个时间戳与当前的时间对比即可。

Ping程序实现步骤

创建类型为SOCK_RAW的一个套接字，同时设定协议IPPROTO_ICMP。
创建并初始化ICMP头。
调用sendto或WSASendto，将ICMP请求发给远程主机。
调用recvfrom或WSARecvfrom，以接收任何ICMP响应。

ping.h

#pragma once

//在默认windows.h会包含winsock.h，当你包含winsock2.h就会冲突，因此在包含windows.h前需要定义一个宏,#define WIN32_LEAN_AND_MEAN ;去除winsock.h

//要么将#include <winsock2.h>放在#include<windows.h>前面或者直接去掉#include<windows.h>

#include <winsock2.h>

#pragma comment(lib, "WS2_32")    // 链接到WS2_32.lib

#define DEF_PACKET_SIZE 32

#define ECHO_REQUEST 8

#define ECHO_REPLY 0

struct IPHeader

{

    BYTE m_byVerHLen; //4位版本+4位首部长度

    BYTE m_byTOS; //服务类型

    USHORT m_usTotalLen; //总长度

    USHORT m_usID; //标识

    USHORT m_usFlagFragOffset; //3位标志+13位片偏移

    BYTE m_byTTL; //TTL

    BYTE m_byProtocol; //协议

    USHORT m_usHChecksum; //首部检验和

    ULONG m_ulSrcIP; //源IP地址

    ULONG m_ulDestIP; //目的IP地址

};

struct ICMPHeader

{

    BYTE m_byType; //类型

    BYTE m_byCode; //代码

    USHORT m_usChecksum; //检验和

    USHORT m_usID; //标识符

    USHORT m_usSeq; //序号

    ULONG m_ulTimeStamp; //时间戳（非标准ICMP头部）

};

struct PingReply

{

    USHORT m_usSeq;

    DWORD m_dwRoundTripTime;

    DWORD m_dwBytes;

    DWORD m_dwTTL;

};

class CPing

{

public:

    CPing();

    ~CPing();

    BOOL Ping(DWORD dwDestIP, PingReply *pPingReply = NULL, DWORD dwTimeout = );

    BOOL Ping(char *szDestIP, PingReply *pPingReply = NULL, DWORD dwTimeout = );

private:

    BOOL PingCore(DWORD dwDestIP, PingReply *pPingReply, DWORD dwTimeout);

    USHORT CalCheckSum(USHORT *pBuffer, int nSize);

    ULONG GetTickCountCalibrate();

private:

    SOCKET m_sockRaw;

    WSAEVENT m_event;

    USHORT m_usCurrentProcID;

    char *m_szICMPData;

    BOOL m_bIsInitSucc;

private:

    static USHORT s_usPacketSeq;

};

ping.cpp

#include "ping.h"

#include <iostream>

USHORT CPing::s_usPacketSeq = ;

CPing::CPing() :m_szICMPData(NULL),m_bIsInitSucc(FALSE)

{

    WSADATA WSAData;

    //WSAStartup(MAKEWORD(2, 2), &WSAData);

    if (WSAStartup(MAKEWORD(, ), &WSAData) != )

    {

        /*如果初始化不成功则报错，GetLastError()返回发生的错误信息*/

        printf("WSAStartup() failed: %d\n", GetLastError());

        return;

    }

    m_event = WSACreateEvent();

    m_usCurrentProcID = (USHORT)GetCurrentProcessId();

    //setsockopt(m_sockRaw);

    /*if ((m_sockRaw = WSASocket(AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, 0, 0)) != SOCKET_ERROR)

    {

        WSAEventSelect(m_sockRaw, m_event, FD_READ);

        m_bIsInitSucc = TRUE;

        m_szICMPData = (char*)malloc(DEF_PACKET_SIZE + sizeof(ICMPHeader));

        if (m_szICMPData == NULL)

        {

            m_bIsInitSucc = FALSE;

        }

    }*/

    m_sockRaw = WSASocket(AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, , );

    if (m_sockRaw == INVALID_SOCKET)

    {

        std::cerr << "WSASocket() failed:" << WSAGetLastError ()<< std::endl;  //10013 以一种访问权限不允许的方式做了一个访问套接字的尝试。

    }

    else

    {

        WSAEventSelect(m_sockRaw, m_event, FD_READ);

        m_bIsInitSucc = TRUE;

        m_szICMPData = (char*)malloc(DEF_PACKET_SIZE + sizeof(ICMPHeader));

        if (m_szICMPData == NULL)

        {

            m_bIsInitSucc = FALSE;

        }

    }

}

CPing::~CPing()

{

    WSACleanup();

    if (NULL != m_szICMPData)

    {

        free(m_szICMPData);

        m_szICMPData = NULL;

    }

}

BOOL CPing::Ping(DWORD dwDestIP, PingReply *pPingReply, DWORD dwTimeout)

{

    return PingCore(dwDestIP, pPingReply, dwTimeout);

}

BOOL CPing::Ping(char *szDestIP, PingReply *pPingReply, DWORD dwTimeout)

{

    if (NULL != szDestIP)

    {

        return PingCore(inet_addr(szDestIP), pPingReply, dwTimeout);

    }

    return FALSE;

}

BOOL CPing::PingCore(DWORD dwDestIP, PingReply *pPingReply, DWORD dwTimeout)

{

    //判断初始化是否成功

    if (!m_bIsInitSucc)

    {

        return FALSE;

    }

    //配置SOCKET

    sockaddr_in sockaddrDest;

    sockaddrDest.sin_family = AF_INET;

    sockaddrDest.sin_addr.s_addr = dwDestIP;

    int nSockaddrDestSize = sizeof(sockaddrDest);

    //构建ICMP包

    int nICMPDataSize = DEF_PACKET_SIZE + sizeof(ICMPHeader);

    ULONG ulSendTimestamp = GetTickCountCalibrate();

    USHORT usSeq = ++s_usPacketSeq;

    memset(m_szICMPData, , nICMPDataSize);

    ICMPHeader *pICMPHeader = (ICMPHeader*)m_szICMPData;

    pICMPHeader->m_byType = ECHO_REQUEST;

    pICMPHeader->m_byCode = ;

    pICMPHeader->m_usID = m_usCurrentProcID;

    pICMPHeader->m_usSeq = usSeq;

    pICMPHeader->m_ulTimeStamp = ulSendTimestamp;

    pICMPHeader->m_usChecksum = CalCheckSum((USHORT*)m_szICMPData, nICMPDataSize);

    //发送ICMP报文

    if (sendto(m_sockRaw, m_szICMPData, nICMPDataSize, , (struct sockaddr*)&sockaddrDest, nSockaddrDestSize) == SOCKET_ERROR)

    {

        return FALSE;

    }

    //判断是否需要接收相应报文

    if (pPingReply == NULL)

    {

        return TRUE;

    }

    char recvbuf[] = { "\0" };

    while (TRUE)

    {

        //接收响应报文

        if (WSAWaitForMultipleEvents(, &m_event, FALSE, , FALSE) != WSA_WAIT_TIMEOUT)

        {

            WSANETWORKEVENTS netEvent;

            WSAEnumNetworkEvents(m_sockRaw, m_event, &netEvent);

            if (netEvent.lNetworkEvents & FD_READ)

            {

                ULONG nRecvTimestamp = GetTickCountCalibrate();

                int nPacketSize = recvfrom(m_sockRaw, recvbuf, , , (struct sockaddr*)&sockaddrDest, &nSockaddrDestSize);

                if (nPacketSize != SOCKET_ERROR)

                {

                    IPHeader *pIPHeader = (IPHeader*)recvbuf;

                    USHORT usIPHeaderLen = (USHORT)((pIPHeader->m_byVerHLen & 0x0f) * );

                    ICMPHeader *pICMPHeader = (ICMPHeader*)(recvbuf + usIPHeaderLen);

                    if (pICMPHeader->m_usID == m_usCurrentProcID //是当前进程发出的报文

                        && pICMPHeader->m_byType == ECHO_REPLY //是ICMP响应报文

                        && pICMPHeader->m_usSeq == usSeq //是本次请求报文的响应报文

                        )

                    {

                        pPingReply->m_usSeq = usSeq;

                        pPingReply->m_dwRoundTripTime = nRecvTimestamp - pICMPHeader->m_ulTimeStamp;

                        pPingReply->m_dwBytes = nPacketSize - usIPHeaderLen - sizeof(ICMPHeader);

                        pPingReply->m_dwTTL = pIPHeader->m_byTTL;

                        return TRUE;

                    }

                }

            }

        }

        //超时

        if (GetTickCountCalibrate() - ulSendTimestamp >= dwTimeout)

        {

            return FALSE;

        }

    }

}

USHORT CPing::CalCheckSum(USHORT *pBuffer, int nSize)

{

    unsigned long ulCheckSum = ;

    while (nSize > )

    {

        ulCheckSum += *pBuffer++;

        nSize -= sizeof(USHORT);

    }

    if (nSize)

    {

        ulCheckSum += *(UCHAR*)pBuffer;

    }

    ulCheckSum = (ulCheckSum >> ) + (ulCheckSum & 0xffff);

    ulCheckSum += (ulCheckSum >> );

    return (USHORT)(~ulCheckSum);

}

ULONG CPing::GetTickCountCalibrate()

{

    static ULONG s_ulFirstCallTick = ;

    static LONGLONG s_ullFirstCallTickMS = ;

    SYSTEMTIME systemtime;

    FILETIME filetime;

    GetLocalTime(&systemtime);

    SystemTimeToFileTime(&systemtime, &filetime);

    LARGE_INTEGER liCurrentTime;

    liCurrentTime.HighPart = filetime.dwHighDateTime;

    liCurrentTime.LowPart = filetime.dwLowDateTime;

    LONGLONG llCurrentTimeMS = liCurrentTime.QuadPart / ;

    if (s_ulFirstCallTick == )

    {

        s_ulFirstCallTick = GetTickCount();

    }

    if (s_ullFirstCallTickMS == )

    {

        s_ullFirstCallTickMS = llCurrentTimeMS;

    }

    return s_ulFirstCallTick + (ULONG)(llCurrentTimeMS - s_ullFirstCallTickMS);

}

main.cpp

#include <winsock2.h>

#include <stdio.h>

#include "ping.h"

int main(void)

{

    CPing objPing;

    char *szDestIP = "127.0.0.1";

    PingReply reply;

    printf("Pinging %s with %d bytes of data:\n", szDestIP, DEF_PACKET_SIZE);

    while (TRUE)

    {

        objPing.Ping(szDestIP, &reply);

        printf("Reply from %s: bytes=%d time=%ldms TTL=%ld\n", szDestIP, reply.m_dwBytes, reply.m_dwRoundTripTime, reply.m_dwTTL);

        Sleep();

    }

    return ;

}

结果：