/* stksrv.c: *  * Example Stock Index Broadcast : */#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>#ifndef TRUE#define TRUE    1#define FALSE   0#endifextern int mkaddr(    void *addr,    int *addrlen,    char *str_addr,    char *protocol);#define MAXQ    4static struct {    char    *index;    int     start;    int     volit;    int     current;} quotes[] = {    { "DJIA",    1030330, 375 },    { "NASDAQ",  276175,  125 },    { "S&P 500", 128331,   50 },    { "TSE 300", 689572,   75 },};/* * Initialize : */static voidinitialize(void) {    short x;    time_t td;    /*     * Seed the random number generator :     */    time(&td);    srand((int)td);    for ( x=0; x < MAXQ; ++x )        quotes[x].current =            quotes[x].start;}/* * Randomly change one index quotation : */static voidgen_quote(void) {    short x;    /* Index */    short v;    /* Volatility of index */    short h;    /* Half of v */    short r;    /* Random change */    x = rand() % MAXQ;    v = quotes[x].volit;    h = (v / 2) - 2;    r = rand() % v;    if ( r < h )        r = -r;    quotes[x].current += r;}/* * 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) {    short x;     /* index of Stock Indexes */    double I0;      /* Initial index value */    double I;               /* Index value */    char bcbuf[512], *bp;/* Buffer and ptr */    int z;           /* Status return code */    int s;                       /* Socket */    struct sockaddr_in adr_srvr;/* AF_INET */    int len_srvr;               /* length  */    struct sockaddr_in adr_bc;  /* AF_INET */    int len_bc;                 /* length  */    static int so_broadcast = TRUE;    static char        *sv_addr = "127.0.0.1:*",        *bc_addr = "127.255.255.255:9097";    /*     * Form a server address :     */    if ( argc > 2 )        /* Server address : */        sv_addr = argv[2];    if ( argc > 1 )        /* Broadcast address : */        bc_addr = argv[1];    /*     * Form the server address :     */    len_srvr = sizeof adr_srvr;    z = mkaddr(        &adr_srvr,  /* Returned address */        &len_srvr,  /* Returned length */        sv_addr,    /* Input string addr */        "udp");     /* UDP protocol */    if ( z == -1 )        bail("Bad server address");    /*     * Form the broadcast address :     */    len_bc = sizeof adr_bc;    z = mkaddr(        &adr_bc,    /* Returned address */        &len_bc,    /* Returned length */        bc_addr,    /* Input string addr */        "udp");     /* UDP protocol */    if ( z == -1 )        bail("Bad broadcast address");    /*     * Create a UDP socket to use :     */    s = socket(AF_INET,SOCK_DGRAM,0);    if ( s == -1 )        bail("socket()");    /*     * Allow broadcasts :     */    z = setsockopt(s,        SOL_SOCKET,        SO_BROADCAST,        &so_broadcast,        sizeof so_broadcast);    if ( z == -1 )        bail("setsockopt(SO_BROADCAST)");    /*     * Bind a address to our socket, so that     * client programs can listen to this     * server:     */    z = bind(s,        (struct sockaddr *)&adr_srvr,        len_srvr);    if ( z == -1 )        bail("bind()");    /*     * Now start serving quotes :     */    initialize();    for (;;) {        /*         * Update one quote in the list:         */        gen_quote();        /*         * Form a packet to send out :         */        bp = bcbuf;        for ( x=0; x<MAXQ; ++x ) {            I0 = quotes[x].start / 100.0;            I = quotes[x].current / 100.0;            sprintf(bp,                "%-7.7s %8.2f %+.2f\n",                quotes[x].index,                I,                I - I0);            bp += strlen(bp);        }            /*         * Broadcast the updated info:         */        z = sendto(s,            bcbuf,            strlen(bcbuf),            0,            (struct sockaddr *)&adr_bc,            len_bc);        if ( z == -1 )            bail("sendto()");        sleep(4);    }    return 0;}