static void    sig_alrm(int);void dg_cli(FILE *fp, int sockfd, const SA *pservaddr, socklen_t servlen){    int    n;    char   sendline[MAXLINE], recvline[MAXLINE + 1];    signal(SIGALRM, sig_alrm);    while (fgets(sendline, MAXLINE, fp) != NULL) {        sendto(sockfd, sendline, strlen(sendline), 0, pservaddr, servlen);        alarm(5);        if ( (n = recvfrom(sockfd, recvline, MAXLINE, 0, NULL, NULL)) < 0) {            if (errno == EINTR)                fprintf(stderr, "socket timeout\n");            else                err_sys("recvfrom error");        } else {            alarm(0);            recvline[n] = 0; /* null terminate */            fputs(recvline, stdout);        }    }}static void sig_alrm(int signo){    return;                  /* just interrupt the recvfrom() */}