VC++实现ping探测远程主机是否可达

1 课程设计目的（1）了解探测远程主机是否可达的方法。

（2）了解windows网络编程的基本步骤。

（3）了解TCP/IP协议及ICMP协议。

（4）掌握ping命令的思想。

（5）掌握Windows Socket API的使用方法。

2 课程设计原理ICMP：互联网控制报文协议，提供一个特殊的报文在互联网的结点之间进行监测和控制，测试目的主机是否可达，与本次课程设计目的一致，因此可模拟ICMP的工作方式来编制程序。

首先通过生成一个ICMP“回应请求”，然后将其定向至打算查询的目标主机，远程主机会拦截这个请求，然后生成一条回应答复消息，再通过网络回传给我们。

若是不能抵达目标主机，则会生成相应的错误消息。

具体步骤如下：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将ICMP请求发给远程主机。

4）调用recvfrom以接收ICMP响应。

其流程图如下：开始启动Winsock获取关键参数：目的主机地址创建套接字，协议字段：ICMP设置发送和接收数据最长等待时间timeout填写目的主机信息建立ICMP数据包int i=0发送和接收数据包一次，i++i<4?释放内存，关闭Winsock结束是否3程序源代码及运行结果3．1 源代码#include <winsock2.h>#include <iostream.h>#pragma comment( lib, "ws2_32.lib" )#define ICMP_ECHO 8 //回应请求类型的ICMP消息类型#define ICMP_ECHOREPLY 0 //回应答复型的ICMP消息类型#define ICMP_MIN 8 // ICMP数据报最小长度#define DEF_PACKET_SIZE 32 //默认数据报大小#define DEF_PACKET_NUMBER 4 //发送数据报的个数#define MAX_PACKET 1024 //最大ICMP数据报大小char *Ipdest; //目标主机的IP地址int datasize; //ICMP消息的长度//接收到的ICMP消息数，每收到一条ICMP消息就加1static int icmpcount=0;//IP头(20字节)struct IPHEAD{unsigned int headlength:4; // 4位头长度unsigned int version:4; // 4位版本unsigned char tos; // 8位服务类型unsigned short totallength; // 16位总长unsigned short ip_id; // 16位标识unsigned short frag_and_flags; //3个一位标识加分段偏移 unsigned char ttl; //8位存活时间unsigned char protocal; //8位协议类型unsigned short ip_checksum; //16位头校验和unsigned int sourceIP; //32位源IP地址unsigned int destIP; //32位目标IP地址};// ICMP 头(12字节)struct ICMPHEAD{unsigned char type; //类型（0，8）unsigned char code; //代码（0)unsigned short icmp_checksum; //校验和unsigned short icmp_id; //标识符unsigned short seq; //序号unsigned long timestamp; //时间戳};//Fill_icmp_data函数:用于设置ICMP头部，填充ICMP消息void Fill_icmp_data(char * icmp_data, int datasize){ICMPHEAD *icmphead=NULL;char *datapart=NULL;icmphead = (ICMPHEAD*)icmp_data;icmphead->type = ICMP_ECHO; //ICMP_ECHO=8icmphead->code = 0; //类型为8，代码为0，表示回应请求icmphead->icmp_checksum = 0;icmphead->icmp_id = (unsigned short)GetCurrentProcessId();datapart = icmp_data + sizeof(ICMPHEAD);//具体内容的首地址指针//初始化数据包内容部分for(int i=0;i<(datasize-sizeof(ICMPHEAD));i++,datapart++) *datapart=0;}//DecodeICMPHEAD函数：接受数据时从IP头中获取ICMP消息void DecodeICMPHEAD(char *recvbuf, int bread, sockaddr_in *from) {IPHEAD *iphead=NULL;ICMPHEAD *icmphead=NULL;DWORD tick;unsigned short iphdrlen;iphead = (IPHEAD *)recvbuf;//32位字的个数乘以4即字节个数iphdrlen = (iphead->headlength) * 4 ;//获取操作系统启动至今所经过的时间（ms)tick=GetTickCount();if (bread < (iphdrlen + ICMP_MIN)){cout<<"Too few bytes from: "<<inet_ntoa(from->sin_addr);cout<<endl;}icmphead = (ICMPHEAD*)(recvbuf + iphdrlen); //ICMP消息始于IP 头之后//若ICMP消息类型并非查询，则输出相应信息类型if (icmphead->type != ICMP_ECHOREPLY){cout<<"nonecho type "<<int(icmphead->type)<<" received";cout<<endl;}//确认收到的应答ICMP消息是否是对发送出去的消息的回应//若其表示与当前进程不符，则输出出错信息if (icmphead->icmp_id != (unsigned short)GetCurrentProcessId()) {cout<<"It's someone else's packet!"<<endl;return;}//输出收到信息的内容:主机地址，icmp消息序号，回应时间,存活时间cout<<"Reply from "<<inet_ntoa(from->sin_addr);cout<<" bytes="<<bread-iphdrlen;cout<<" time: "<<GetTickCount()-icmphead->timestamp<<" ms ";cout<<" seq="<<icmphead->seq;cout<<endl;icmpcount++;}//Checksum函数：用于求ICMP首部校验和unsigned short Checksum(unsigned short *buffer, int size){unsigned long cksum=0; //设校验和初值为0while(size >1){cksum+=*buffer++; //求各个16位数字之和size -=sizeof(unsigned short);}if(size){cksum += *(unsigned char*)buffer;}cksum = (cksum >> 16) + (cksum & 0xffff); //高位与低位相加cksum += (cksum >>16); //加上进位return (unsigned short)(~cksum); //取反得到校验和}//Usage函数：表示程序的功能void Usage(char *progname){cout<<"Usage:"<<progname<<" <host>"<<endl;cout<<" host remote machine to Ping"<<endl;cout<<endl;}//ValidateArgs函数：用于给目的地址和数据包大小赋值void ValidateArgs(int argc,char **argv){datasize=DEF_PACKET_SIZE; //数据包大小为DEF_PACKET_SIZE=32if(argc<2){Usage(argv[0]); //只输入一个参数：程序名Ipdest="202.119.81.120"; //默认目的地址为：202.119.81.120 }else if(argc==2)Ipdest=argv[1]; //第二个参数为目的地址}//main函数：进行建立套接字，创建ICMP头，设置超时时间，发送和接受数据等。

int main(int argc,char**argv){WSADATA wsaData;SOCKET sockRaw=INVALID_SOCKET;sockaddr_in dest,from;int destlen=sizeof(dest),fromlen=sizeof(from),bwrote,bread;char *icmp_data=NULL,*recvbuf=NULL;struct hostent *hp=NULL;unsigned short seq=0;//启动winsock失败，输出错误提示信息if (WSAStartup(MAKEWORD(2,2),&wsaData) != 0){cout<<"WSAStartup failed:"<<GetLastError();cout<<endl;return -1;}ValidateArgs(argc,argv);//创建套接字失败，输出错误信息提示sockRaw = WSASocket(AF_INET,SOCK_RAW,IPPROTO_ICMP,NULL, 0,WSA_FLAG_OVERLAPPED);if (sockRaw == INVALID_SOCKET){cout<<"WSASocket() failed:"<<GetLastError();cout<<endl;return -1;}//设定发送数据时最长等待时间timeout=1000msint timeout=1000;bread=setsockopt(sockRaw,SOL_SOCKET,SO_RCVTIMEO,(char *)&timeout,sizeof(timeout));if(bread==SOCKET_ERROR){cout<<"setsockopt(SO_RCVTIMEO)failed:"<<WSAGetLastError();cout<<endl;return -1;}//设定接收数据时最长等待时间timeout=1000mstimeout=1000;bread=setsockopt(sockRaw,SOL_SOCKET,SO_SNDTIMEO,(char *)&timeout,sizeof(timeout));if(bread==SOCKET_ERROR){cout<<"setsockopt(SO_SNDTIMEO) failed:"<<WSAGetLastError();cout<<endl;return -1;}//解析目的地址的名称dest.sin_family=AF_INET;if(dest.sin_addr.s_addr=inet_addr(Ipdest)){//inet_addr将IP地址转换成网络地址if((hp=gethostbyname(Ipdest))!=NULL){//gethostbyname主机信息memcpy(&(dest.sin_addr),hp->h_addr,hp->h_length); //复制内存dest.sin_family=hp->h_addrtype;cout<<"dest.sin_addr="<<inet_ntoa(dest.sin_addr);cout<<endl<<'\n';}else{cout<<"gethostbyname() failed:"<<WSAGetLastError();cout<<endl;return -1;}}//建立一个ICMP数据包datasize+=sizeof(ICMPHEAD);//为要发送的数据申请内存空间，最大值为1024icmp_data=new char[MAX_PACKET];//为要接收的数据申请内存空间，最大值为1024recvbuf=new char[MAX_PACKET];//分配内存失败，输出提示信息if(!icmp_data){cout<<"new char[] failed:"<<WSAGetLastError();cout<<endl;return -1;}//将ICMP信息所在空间清零memset(icmp_data,0,MAX_PACKET);//设置ICMP信息头部Fill_icmp_data(icmp_data,datasize);//发送和接收数据,循环四次for(int i=0;i<4;i++){//ICMP信息封装((ICMPHEAD*)icmp_data)->icmp_checksum=0;((ICMPHEAD*)icmp_data)->timestamp = GetTickCount();((ICMPHEAD*)icmp_data)->seq=seq++;((ICMPHEAD*)icmp_data)->icmp_checksum =Checksum((unsigned short*)icmp_data,datasize);//发送数据bwrote = sendto(sockRaw,icmp_data,datasize,0,(sockaddr*)&dest,destlen);if (bwrote == SOCKET_ERROR){if (WSAGetLastError() == WSAETIMEDOUT){cout<<"Request timed out."<<endl;continue;}else{cout<<"sendto( ) failed:"<<WSAGetLastError();cout<<endl;return -1;}}//显示实际发送的字节数cout<<"Pinging "<<inet_ntoa(dest.sin_addr)<<" with ";cout<<bwrote<<" bytes of data:";cout<<endl;//接收数据bread=recvfrom(sockRaw,recvbuf,MAX_PACKET,0,(sockaddr*)&from,&fromlen);if (bread == SOCKET_ERROR){if (WSAGetLastError() == WSAETIMEDOUT){cout<<"Request timed out."<<endl;continue;}cout<<"recvfrom() failed: "<<WSAGetLastError();cout<<endl;return -1;}//打开接收到的数据，从中提取ICMP头信息DecodeICMPHEAD(recvbuf,bread,&from);//等待1s钟Sleep(1000);}//输出发送的数据包数、接收的数据包数和丢失的数据包数cout<<endl;cout<<"Ping statistics for "<<inet_ntoa(dest.sin_addr)<<":"<<endl;cout<<" Packets:sent=4,";cout<<"Received="<<icmpcount;cout<<",Lost="<<DEF_PACKET_NUMBER-icmpcount;cout<<"("<<((float)(DEF_PACKET_NUMBER-icmpcount)/DEF_PACKET_NU MBER)*100;cout<<"%loss)";cout<<endl;//释放资源,关闭winsockif(sockRaw!=INVALID_SOCKET)closesocket(sockRaw);delete[] recvbuf;delete[] icmp_data;WSACleanup();return 0;}3．2 运行结果点击“开始”——“运行”——“cmd”，输入“C:\program1\Debug\zpp.exe+目标主机地址”即可运行程序。