linux c++ ping

你想要了解如何在 Linux C++ 中实现 ping 功能吗？如果是的话，下面是一个简单的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/ip_icmp.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <sys/time.h>

#define PACKET_SIZE 4096

struct packet
{
    struct icmphdr hdr;
    char msg[PACKET_SIZE-sizeof(struct icmphdr)];
};

unsigned short checksum(void *b, int len)
{
    unsigned short *buf = (unsigned short *)b;
    unsigned int sum = 0;
    unsigned short result;

    for (sum = 0; len > 1; len -= 2)
    {
        sum += *buf++;
    }

    if (len == 1)
    {
        sum += *(unsigned char *)buf;
    }

    sum = (sum >> 16) + (sum & 0xFFFF);
    sum += (sum >> 16);
    result = ~sum;

    return result;
}

int main(int argc, char *argv[])
{
    if (argc < 2)
    {
        printf("Usage: %s <hostname/IP address>\n", argv[0]);
        return 1;
    }

    struct hostent *host = gethostbyname(argv[1]);
    if (host == NULL)
    {
        printf("Failed to resolve hostname\n");
        return 1;
    }

    struct sockaddr_in addr;
    addr.sin_family = AF_INET;
    addr.sin_port = 0;
    addr.sin_addr.s_addr = *(unsigned long *)host->h_addr_list[0];

    int sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
    if (sockfd < 0)
    {
        printf("Failed to create socket\n");
        return 1;
    }

    struct timeval tv;
    tv.tv_sec = 5;
    tv.tv_usec = 0;
    if (setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, (const char*)&tv, sizeof(tv)) < 0)
    {
        printf("Failed to set socket options\n");
        return 1;
    }

    struct packet pckt;
    memset(&pckt, 0, sizeof(pckt));
    pckt.hdr.type = ICMP_ECHO;
    pckt.hdr.un.echo.id = getpid();
    memset(pckt.msg, 'a', sizeof(pckt.msg)-1);
    pckt.msg[sizeof(pckt.msg)-1] = 0;
    pckt.hdr.un.echo.sequence = 0;
    pckt.hdr.checksum = checksum(&pckt, sizeof(pckt));

    struct sockaddr_in r_addr;
    socklen_t r_addr_len = sizeof(r_addr);

    struct timeval start;
    gettimeofday(&start, NULL);

    int sent = sendto(sockfd, &pckt, sizeof(pckt), 0, (struct sockaddr*)&addr, sizeof(addr));
    if (sent <= 0)
    {
        printf("Failed to send ICMP packet\n");
        return 1;
    }

    char buf[PACKET_SIZE];
    int received = recvfrom(sockfd, buf, sizeof(buf), 0, (struct sockaddr*)&r_addr, &r_addr_len);
    if (received <= 0)
    {
        printf("Failed to receive ICMP packet\n");
        return 1;
    }

    struct timeval end;
    gettimeofday(&end, NULL);

    double rtt = (double)(end.tv_sec-start.tv_sec)*1000.0 + (double)(end.tv_usec-start.tv_usec)/1000.0;

    printf("Received ICMP packet from %s, rtt: %f ms\n", inet_ntoa(r_addr.sin_addr), rtt);

    close(sockfd);

    return 0;
}

这个代码可以通过 ICMP 协议向目标主机发送 ping 命令，并接收回复，从而计算出 RTT（Round Trip Time）即往返时间。需要注意的是，这个代码需要在 root 权限下运行，否则会出现权限不足的错误。