LinuxC++实现一个简易版的ping(也就是imcp协议)
背景:
想实现一个在没外网的时候就自动重启路由器的功能。
又不想用ping命令,因为在代码里调用system("ping"); 可能会比较耗时,得单开线程。于是找了个实现ICMP协议的代码。
参考:https://blog.csdn.net/qivan/article/details/7237051
代码:
#include <stdio.h> #include <sys/socket.h> #include <netinet/in.h> #include <netinet/ip.h> #include <netinet/ip_icmp.h> #include <arpa/inet.h> #include <sys/types.h> #include <sys/time.h> #include <unistd.h> #include <netdb.h> #include <string.h> #define PACKET_SIZE 4096 #define ERROR 0 #define SUCCESS 1 //效验算法(百度下有注释,但是还是看不太明白) unsigned short cal_chksum(unsigned short *addr, 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); sum += (sum >> 16); answer = ~sum; return answer; } // Ping函数 int ping( char *ips, int timeout) { struct timeval *tval; int maxfds = 0; fd_set readfds; struct sockaddr_in addr; struct sockaddr_in from; // 设定Ip信息 bzero(&addr,sizeof(addr)); addr.sin_family = AF_INET; addr.sin_addr.s_addr = inet_addr(ips); #if 1 int sockfd; // 取得socket 。 如果没加sudo 这里会报错 sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP); if (sockfd < 0) { printf("ip:%s,socket error\n",ips); return ERROR; } struct timeval timeo; // 设定TimeOut时间 timeo.tv_sec = timeout / 1000; timeo.tv_usec = timeout % 1000; if (setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, &timeo, sizeof(timeo)) == -1) { printf("ip:%s,setsockopt error\n",ips); return ERROR; } char sendpacket[PACKET_SIZE]; char recvpacket[PACKET_SIZE]; // 设定Ping包 memset(sendpacket, 0, sizeof(sendpacket)); pid_t pid; // 取得PID,作为Ping的Sequence ID pid=getpid(); struct ip *iph; struct icmp *icmp; icmp=(struct icmp*)sendpacket; icmp->icmp_type=ICMP_ECHO; //回显请求 icmp->icmp_code=0; icmp->icmp_cksum=0; icmp->icmp_seq=0; icmp->icmp_id=pid; tval= (struct timeval *)icmp->icmp_data; gettimeofday(tval,NULL); icmp->icmp_cksum=cal_chksum((unsigned short *)icmp,sizeof(struct icmp)); //校验 int n; // 发包 。可以把这个发包挪到循环里面去。 n = sendto(sockfd, (char *)&sendpacket, sizeof(struct icmp), 0, (struct sockaddr *)&addr, sizeof(addr)); if (n < 1) { printf("ip:%s,sendto error\n",ips); return ERROR; } // 接受 // 由于可能接受到其他Ping的应答消息,所以这里要用循环 while(1) { // 设定TimeOut时间,这次才是真正起作用的 FD_ZERO(&readfds); FD_SET(sockfd, &readfds); maxfds = sockfd + 1; n = select(maxfds, &readfds, NULL, NULL, &timeo); if (n <= 0) { printf("ip:%s,Time out error\n",ips); close(sockfd); return ERROR; } // 接受 memset(recvpacket, 0, sizeof(recvpacket)); int fromlen = sizeof(from); n = recvfrom(sockfd, recvpacket, sizeof(recvpacket), 0, (struct sockaddr *)&from, (socklen_t *)&fromlen); printf("recvfrom Len:%d\n",n); if (n < 1) { return ERROR; } char *from_ip = (char *)inet_ntoa(from.sin_addr); // 判断是否是自己Ping的回复 if (strcmp(from_ip,ips) != 0) { printf("NowPingip:%s Fromip:%s NowPingip is not same to Fromip,so ping wrong!\n",ips,from_ip); return ERROR; } iph = (struct ip *)recvpacket; icmp=(struct icmp *)(recvpacket + (iph->ip_hl<<2)); printf("ip:%s,icmp->icmp_type:%d,icmp->icmp_id:%d\n",ips,icmp->icmp_type,icmp->icmp_id); // 判断Ping回复包的状态 if (icmp->icmp_type == ICMP_ECHOREPLY && icmp->icmp_id == pid) //ICMP_ECHOREPLY回显应答 { // 正常就退出循环 printf("icmp succecss ............. \n"); break; } else { // 否则继续等 continue; } } #endif return SUCCESS; } int main() { #if 1 char cPing[16]; printf("Please input ping IP:"); scanf("%s",cPing); #else char *cPing = "192.168.1.200"; #endif if(ping(cPing,10000)) { printf("Ping succeed!\n"); } else { printf("Ping wrong!\n"); } return 0; }
实际效果:
补充说明:
0)直接用参考链接上的代码时编译不过,不知道是不是因为我用的是cpp,没太深究。
1)实际使用的时候需要加上sudo,不然在创建套接字那个地方会报错。我还没想好怎么在代码里用sudo,(因为实际项目运行起来是不需要加sudo的)。