C++实现ping功能<转>

时间:2024-01-02 15:37:14

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:

C++实现ping功能<转>

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:

C++实现ping功能<转>

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:

C++实现ping功能<转>

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

  1. 创建类型为SOCK_RAW的一个套接字,同时设定协议IPPROTO_ICMP。
  2. 创建并初始化ICMP头。
  3. 调用sendto或WSASendto,将ICMP请求发给远程主机。
  4. 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:

C++实现ping功能<转>

附录:如何计算检验和

ICMP中检验和的计算算法为:

1、将检验和字段置为0

2、把需校验的数据看成以16位为单位的数字组成,依次进行二进制反码求和

3、把得到的结果存入检验和字段中

所谓二进制反码求和,就是:

1、将源数据转成反码

2、0+0=0   0+1=1   1+1=0进1

3、若最高位相加后产生进位,则最后得到的结果要加1

在实际实现的过程中,比较常见的代码写法是:

1、将检验和字段置为0

2、把需校验的数据看成以16位为单位的数字组成,依次进行求和,并存到32位的整型中

3、把求和结果中的高16位(进位)加到低16位上,如果还有进位,重复第3步[实际上,这一步最多会执行2次]

4、将这个32位的整型按位取反,并强制转换为16位整型(截断)后返回

其中也遇到了很多问题,头文件包含,WSAStartup函数初始化失败。。。

主要参考:

http://www.cnblogs.com/*/p/4078940.html

http://blog.sina.com.cn/s/blog_5cf5e7c401014fvq.html

http://blog.csdn.net/segen_jaa/article/details/7569727

原贴地址:https://www.cnblogs.com/ranjiewen/p/5704627.html