/* daytime.c: *  * Example daytime client : */#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <errno.h>#include <string.h>#include <sys/types.h>#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <netdb.h>/* * This function reports the error and * exits back to the shell : */static voidbail(const char *on_what) {    fputs(strerror(errno),stderr);    fputs(": ",stderr);    fputs(on_what,stderr);    fputc('\n',stderr);    exit(1);}intmain(int argc,char **argv) {    int z;    char *srvr_addr = NULL;    struct sockaddr_in adr_srvr;/* AF_INET */    int len_inet;               /* length  */    int s;                       /* Socket */    struct servent *sp;   /* Service entry */    char dtbuf[128];     /* Date/Time info */    /*     * Use a server address from the command     * line, if one has been provided.     * Otherwise, this program will default     * to using the arbitrary address     * 127.0.0.1 :     */    if ( argc >= 2 ) {        /* Addr on cmdline: */        srvr_addr = argv[1];    } else {        /* Use default address: */        srvr_addr = "127.0.0.1";    }    /*     * Lookup the daytime tcp service:     */    sp = getservbyname("daytime","tcp");    if ( !sp ) {        fputs("Unknown service: daytime tcp\n",            stderr);        exit(1);    }    /*     * Create a server socket address:     */    memset(&adr_srvr,0,sizeof adr_srvr);    adr_srvr.sin_family = AF_INET;    adr_srvr.sin_port = sp->s_port;    adr_srvr.sin_addr.s_addr =        inet_addr(srvr_addr);    if ( adr_srvr.sin_addr.s_addr == INADDR_NONE )        bail("bad address.");    len_inet = sizeof adr_srvr;    /*     * Create a TDP/IP socket to use :     */    s = socket(PF_INET,SOCK_STREAM,0);    if ( s == -1 )        bail("socket()");    /*     * Connect to the server:     */    z = connect(s,&adr_srvr,len_inet);    if ( z == -1 )        bail("connect(2)");    /*     * Read the date/time info:     */    z = read(s,&dtbuf,sizeof dtbuf-1);    if ( z == -1 )        bail("read(2)");    /*     * Report the Date & Time :     */    dtbuf[z] = 0;   /* null terminate string */    printf("Date & Time is: %s\n",dtbuf);    /*     * Close the socket and exit:     */    close(s);    putchar('\n');    return 0;}