写一段监控网络包的程序

// 写一段监控网络包的程序
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#define BUFSIZE 30

int main(int argc, char *argv[])
{
    int sock;
    char buf[BUFSIZE];
    int str_len;
    socklen_t adr_sz;
    struct sockaddr_in serv_adr, from_adr;
    if (argc != 3)
    {
        printf("Usage : %s <IP> <port>\n", argv[0]);
        exit(1);
    }
    sock = socket(PF_INET, SOCK_DGRAM, 0);
    if (sock == -1)
    {
        printf("socket() error");
    }
    memset(&serv_adr, 0, sizeof(serv_adr));
    serv_adr.sin_family = AF_INET;
    serv_adr.sin_addr.s_addr = inet_addr(argv[1]);
    serv_adr.sin_port = htons(atoi(argv[2]));
    while (1)
    {
        adr_sz = sizeof(from_adr);
        str_len = recvfrom(sock, buf, BUFSIZE, 0,
                           (struct sockaddr *)&from_adr, &adr_sz);
        buf[str_len] = 0;
        printf("Message from server : %s", buf);
    }
    close(sock);
    return 0;
}