利用c语言写网络嗅探器程序

编写网络嗅探器程序需要使用底层的网络编程知识和socket编程知识。以下是一个简单的利用C语言编写的网络嗅探器程序的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netinet/if_ether.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <netinet/udp.h>

int main(int argc, char *argv[]) {
    int sockfd, n;
    char buf[2048];
    struct sockaddr_in addr;
    struct ether_header *eth;
    struct iphdr *iph;
    struct tcphdr *tcph;
    struct udphdr *udph;

    sockfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
    if (sockfd < 0) {
        perror("socket");
        exit(1);
    }

    while (1) {
        n = recvfrom(sockfd, buf, sizeof(buf), 0, NULL, NULL);
        if (n < 42) continue;

        eth = (struct ether_header *)buf;
        if (ntohs(eth->ether_type) != ETHERTYPE_IP) continue;

        iph = (struct iphdr *)(buf + sizeof(struct ether_header));
        if (iph->protocol == IPPROTO_TCP) {
            tcph = (struct tcphdr *)(buf + sizeof(struct ether_header) + sizeof(struct iphdr));
            printf("TCP packet: %s:%d -> %s:%d\n", inet_ntoa(*(struct in_addr *)&iph->saddr),
                                                   ntohs(tcph->source),
                                                   inet_ntoa(*(struct in_addr *)&iph->daddr),
                                                   ntohs(tcph->dest));
        } else if (iph->protocol == IPPROTO_UDP) {
            udph = (struct udphdr *)(buf + sizeof(struct ether_header) + sizeof(struct iphdr));
            printf("UDP packet: %s:%d -> %s:%d\n", inet_ntoa(*(struct in_addr *)&iph->saddr),
                                                   ntohs(udph->source),
                                                   inet_ntoa(*(struct in_addr *)&iph->daddr),
                                                   ntohs(udph->dest));
        }
    }

    close(sockfd);
    return 0;
}

该程序使用了Linux下的AF_PACKET套接字来实现网络嗅探，可以用来捕获传输层协议为TCP或UDP的数据包，并打印出源地址、源端口、目的地址和目的端口。需要注意的是，该程序需要在root权限下运行。