c语言实现ping

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在dos输入ping+主机名可以知道主机是否可达，这是网际控制报文协议ICMP的一个应用，为了更有效的转发IP数据报和提高交付成功机会，封装在ip数据包中的ICMP允许主机或路由器报告差错情况和提供异常情况的报告。更具体点的，向目的主机发送ICMP回送请求报文，收到此报文的主机必须向源主机或路由器发送ICMP回送回答报文。ICMP的报文格式是，常见的ICMP报文类型如下图

要模拟ping的过程，就是先数据封装一个ICMP报文，发送并对接收的ip数据报文处理的过程。以下为代码

#include<stdio.h>#include<Winsock2.h>#include<ws2tcpip.h>#include<stdlib.h>#include<malloc.h>#include<string.h>#pragma comment("WS2_32.lib")#define DEF_ICMP_TIMEOUT 3000  //定义超时为3秒#define ICMP_ECHO_REQUEST 8 //定义回显请求类型#define DEF_ICMP_DATA_SIZE 20 //定义发送数据长度#define DEF_ICMP_PACK_SIZE 32 //定义数据包长度#define MAX_ICMP_PACKET_SIZE 1024 //定义最大数据包长度#define ICMP_ECHO_REPLY 0 //定义回显应答类型/* *IP报头结构 */typedef struct{    byte h_len_ver ; //IP版本号    byte tos ; // 服务类型    unsigned short total_len ; //IP包总长度    unsigned short ident ; // 标识    unsigned short frag_and_flags ; //标志位    byte ttl ; //生存时间    byte proto ; //协议    unsigned short cksum ; //IP首部校验和    unsigned long sourceIP ; //源IP地址    unsigned long destIP ; //目的IP地址} IP_HEADER ;/* *定义ICMP数据类型 */typedef struct{    byte type ; //类型-----8    byte code ; //代码-----8    unsigned short cksum ; //校验和------16    unsigned short id ; //标识符-------16    unsigned short seq ; //序列号------16    unsigned int choose ; //选项-------32} ICMP_HEADER ;typedef struct{    int usSeqNo ; //记录序列号    DWORD dwRoundTripTime ; //记录当前时间    byte ttl ; //生存时间    IN_ADDR dwIPaddr ; //源IP地址} DECODE_RESULT ;//将命令行参数转换为ip地址unsigned long GetIp(char *str){   unsigned long ulDestIP=inet_addr(str);   if(ulDestIP==INADDR_NONE){      HOSTENT *pHostent=gethostbyname(str);      if(pHostent){         ulDestIP=(*(IN_ADDR*)pHostent->h_addr).s_addr;      }      pHostent=gethostbyname("www.baidu.com");       if (pHostent == NULL) {           perror("getaddrinfo");              ulDestIP=2;       }   }   return ulDestIP;}//产生网际校验和unsigned short GenerateChecksum(unsigned short *pBuf,int iSize){   unsigned long cksum=0;   while(iSize>1){     cksum+=*pBuf++;//将待校验的数据每16位逐位相加保存在cksum中     iSize-=sizeof(unsigned short);//每16位加完则将带校验数据量减16   }   //   if(iSize){       cksum+=*(unsigned char *)pBuf;   }   cksum=(cksum>>16)+(cksum&0xffff);   cksum+=(cksum>>16);   return (unsigned short)(~cksum);}//解析应答信息int DecodeIcmpResponse(char *pBuf,int iPacketSize,DECODE_RESULT *stDecodeResult){    //获取收到的IP数据包的首部信息   IP_HEADER *pIpHrd=(IP_HEADER *)pBuf;   int iIpHrdLen=20;   if(iPacketSize<(int)(iIpHrdLen+sizeof(ICMP_HEADER))){      return 0;   }   //指针指向ICMP报文的首地址   ICMP_HEADER *pIcmpHrd=(ICMP_HEADER *)(pBuf+iIpHrdLen);   unsigned short usID,usSquNo;   //获取的数据包的type字段为ICMP_ECHO_REPLY,即受到一个回显应答的报文   if(pIcmpHrd->type==ICMP_ECHO_REPLY){      usID=pIcmpHrd->id;      //接受到的是网络字节顺序的seq字段信息，需要转成主机字节顺序      usSquNo=ntohs(pIcmpHrd->seq);   }   if(usID!=GetCurrentProcessId()||usSquNo!=stDecodeResult->usSeqNo){     return 0;   }   if(pIcmpHrd->type==ICMP_ECHO_REPLY){       stDecodeResult->ttl=pIpHrd->ttl;       stDecodeResult->dwIPaddr.s_addr=pIpHrd->sourceIP;       stDecodeResult->dwRoundTripTime=GetTickCount()-stDecodeResult->dwRoundTripTime;       return 1;   }   return 0;}//填充目的的socketint CreateSocket(unsigned long ulDestIP){    //填充目的的socket   SOCKADDR_IN destSockAddr;   ZeroMemory(&destSockAddr,sizeof(SOCKADDR_IN));   destSockAddr.sin_family=AF_INET;   destSockAddr.sin_addr.s_addr=ulDestIP;   destSockAddr.sin_port = htons(0);   //初始化WinSock    WORD wVersionRequested = MAKEWORD(2,2);    WSADATA wsaData;    if(WSAStartup(wVersionRequested,&wsaData) != 0)    {        printf("初始化WinSock失败！\n") ;        return ;    }//使用ICMP协议创建Raw Socket   SOCKET sockRaw = WSASocket(AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, 0, WSA_FLAG_OVERLAPPED);    if(sockRaw == INVALID_SOCKET)   {       printf("WSASocket() failed: %d\n", WSAGetLastError());       return ;   }   //设置端口属性   int iTimeout=DEF_ICMP_TIMEOUT;   if(setsockopt(sockRaw,SOL_SOCKET, SO_RCVTIMEO,(char *)&iTimeout,sizeof(iTimeout))==SOCKET_ERROR){      printf("设置SO_RCVTIMEO失败\n");   }   if(setsockopt(sockRaw,SOL_SOCKET, SO_SNDTIMEO,(char *)&iTimeout,sizeof(iTimeout))==SOCKET_ERROR){      printf("设置SO_SNDTIMEO失败\n");   }    //定义发送的数据段   char IcmpSendBuf[DEF_ICMP_PACK_SIZE] ;   //填充ICMP数据包各字段   ICMP_HEADER * pIcmpHeader=(ICMP_HEADER *)IcmpSendBuf;   pIcmpHeader->type=ICMP_ECHO_REQUEST;   pIcmpHeader->code=0;   pIcmpHeader->id=(unsigned short)GetCurrentProcessId();   memset(IcmpSendBuf+sizeof(ICMP_HEADER),'E',DEF_ICMP_DATA_SIZE);   //循环发送4个请求回显icmp数据包   DECODE_RESULT stDecodeResult;   int usSeqNo;   for(usSeqNo=0;usSeqNo<=3;usSeqNo++){      pIcmpHeader->seq=htons(usSeqNo);      pIcmpHeader->cksum=0;      pIcmpHeader->cksum=GenerateChecksum((unsigned short *)IcmpSendBuf,sizeof(ICMP_HEADER)+DEF_ICMP_DATA_SIZE);      //记录序列号和当前时间      stDecodeResult.usSeqNo=usSeqNo;      stDecodeResult.dwRoundTripTime=GetTickCount();      //发送ICMP的EchoRequest数据包      if(sendto(sockRaw,IcmpSendBuf,sizeof(IcmpSendBuf),0,(SOCKADDR*)&destSockAddr,sizeof(destSockAddr))==SOCKET_ERROR){         //如果主机不可达则直接退出         if(WSAGetLastError()==WSAEHOSTUNREACH){              return 0;         }      }      SOCKADDR_IN from;      int iFromLen=sizeof(from);      int iReadLen;       //定义接收的数据包      char IcmpRecvBuf[MAX_ICMP_PACKET_SIZE] ;      while(1){        iReadLen=recvfrom(sockRaw,IcmpRecvBuf,MAX_ICMP_PACKET_SIZE,0,(SOCKADDR*)&from,&iFromLen);        if(iReadLen!=SOCKET_ERROR){//正确接受到一个ICMP报文             if(DecodeIcmpResponse(IcmpRecvBuf , sizeof(IcmpRecvBuf) , &stDecodeResult)==1)             {                printf("来自 %s 的回复: 字节 = %d 时间 = %dms TTL = %d\n" , inet_ntoa(stDecodeResult.dwIPaddr) ,                         iReadLen - 20,stDecodeResult.dwRoundTripTime ,stDecodeResult.ttl) ;             }             break ;        }else if(WSAGetLastError()==WSAETIMEDOUT){//接受超时              printf("time out !  *****\n") ;              break ;        }else{             printf("发生未知错误！\n") ;             break ;        }      }   }   printf("\nping complete.\n");   closesocket(sockRaw);   WSACleanup();   return 0;}int main(int argc,char *argv[]){    char *arr=(char *)malloc(sizeof(char));    unsigned long ulDestIP;//ip地址    if(argv[1]!=NULL){       ulDestIP=GetIp(argv[1]);    }else{       printf("请输入ip地址：");       scanf("%s",arr);       ulDestIP=GetIp(arr);    }    CreateSocket(ulDestIP);}

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