/* server.c: *  * Example daytime server : */#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <errno.h>#include <string.h>#include <time.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) {    if ( errno != 0 ) {        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;    char *srvr_port = "9099";    struct sockaddr_in adr_srvr;/* AF_INET */    struct sockaddr_in adr_clnt;/* AF_INET */    int len_inet;               /* length  */    int s;                       /* Socket */    int c;                /* Client socket */    int n;                        /* bytes */    time_t td;        /* Current date&time */    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";    }    /*     * If there is a second argument on the     * command line, use it as the port # :     */    if ( argc >= 3 )        srvr_port = argv[2];    /*     * Create a TDP/IP socket to use :     */    s = socket(PF_INET,SOCK_STREAM,0);    if ( s == -1 )        bail("socket()");    /*     * Create a server socket address:     */    memset(&adr_srvr,0,sizeof adr_srvr);    adr_srvr.sin_family = AF_INET;    adr_srvr.sin_port = htons(atoi(srvr_port));    if ( strcmp(srvr_addr,"*") != 0 ) {        /* Normal Address */        adr_srvr.sin_addr.s_addr =            inet_addr(srvr_addr);        if ( adr_srvr.sin_addr.s_addr             == INADDR_NONE )            bail("bad address.");    } else {        /* Wild Address */        adr_srvr.sin_addr.s_addr =            INADDR_ANY;    }    /*     * Bind the server address:     */    len_inet = sizeof adr_srvr;    z = bind(s,(struct sockaddr *)&adr_srvr,            len_inet);    if ( z == -1 )        bail("bind(2)");    /*     * Make it a listening socket:     */    z = listen(s,10);    if ( z == -1 )        bail("listen(2)");    /*     * Start the server loop :     */    for (;;) {        /*         * Wait for a connect :         */        len_inet = sizeof adr_clnt;        c = accept(s,            (struct sockaddr *)&adr_clnt,            &len_inet);        if ( c == -1 )            bail("accept(2)");        /*         * Generate a time stamp :         */        time(&td);        n = (int) strftime(dtbuf,sizeof dtbuf,            "%A %b %d %H:%M:%S %Y\n",            localtime(&td));        /*         * Write result back to the client :         */        z = write(c,dtbuf,n);        if ( z == -1 )            bail("write(2)");        /*         * Close this client's connection:         */        close(c);    }    /* Control never gets here */    return 0;}