c

#include"net.h"
void usage(char *s)
{
    printf("\nthis is udp\n");
    printf("\nusage:\n\t %s serv_ip serv_port",s);
    printf("\n\t serv_ip:udp server ip address");
    printf("\n\t serv_port:udp server port\n\n");
}
int main(int argc,char *argv[])
{
    int fd = -1;
    int port = SERV_PORT;
    port = atoi(argv[2]);
    if(port < 0 || (port > 0 && port <= 5000))
    {
        usage(argv[0]);
        exit(1);
    }
    struct sockaddr_in sin;
    if(argc != 3)
    {
        usage(argv[0]);
        exit(1);
    }
    //1
    if((fd = socket(AF_INET,SOCK_DGRAM,0)) < 0)
    {
        perror("socket");
        exit(1);
    }
    sin.sin_family = AF_INET;
    sin.sin_port = htons (SERV_PORT);
    if (inet_pton (AF_INET, argv[1], (void *) &sin.sin_addr) != 1) {
        perror ("inet_pton");
        exit (1);
    }
    printf("udp client starting...ok\n");
    char buf[BUFSIZ];
    while(1)
    {
        bzero(buf,BUFSIZ);
        if(fgets(buf,BUFSIZ-1,stdin) == NULL)
        {
            perror("fgets");
            continue;
        }
        sendto(fd,buf,strlen(buf),0,(struct sockaddr *)&sin,sizeof(sin));
        if (!strncasecmp (buf, QUIT_STR, strlen (QUIT_STR))) 
        {
            printf ("Client is exiting!\n");
            break;
        }
    }
    close(fd);
    return 0;
}