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glacjay/gist:856270

Created March 5, 2011 09:59
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  1. glacjay created this gist Mar 5, 2011.
    142 changes: 142 additions & 0 deletions gistfile1.c
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,142 @@
    #include <stdio.h>
    #include <stdlib.h>
    #include <errno.h>
    #include <string.h>

    #include <sys/socket.h>
    #include <netinet/in.h>
    #include <pthread.h>
    #include <unistd.h>
    #include <arpa/inet.h>

    #define PORT 5460

    static char *progname;
    static int sock;

    static void usage(void)
    {
    fprintf(stderr,
    "Usage: %s options\n"
    "where options must be one of:\n"
    " -s <name> Running as a <name> named server.\n"
    " -c <name> Asking for <name>'s address.\n",
    progname);
    exit(1);
    }

    static int udp_socket(void)
    {
    int sock = socket(PF_INET, SOCK_DGRAM, 0);
    if (sock == -1) {
    fprintf(stderr, "Cannot open a new socket: %s\n", strerror(errno));
    exit(1);
    }
    return sock;
    }

    static void server(const char *name)
    {
    struct sockaddr_in listen_addr;

    listen_addr.sin_family = AF_INET;
    listen_addr.sin_addr.s_addr = INADDR_ANY;
    listen_addr.sin_port = htons(PORT);

    if (bind(sock, (struct sockaddr *) &listen_addr,
    sizeof(listen_addr)) == -1)
    {
    fprintf(stderr, "Cannot bind to the UDP port %d: %s\n",
    PORT, strerror(errno));
    exit(1);
    }

    while (1) {
    char buf[BUFSIZ+1];
    struct sockaddr_in addr;
    int addrlen = sizeof(addr);
    int received;

    received = recvfrom(sock, buf, sizeof(buf)-1, 0,
    (struct sockaddr *) &addr, (socklen_t *) &addrlen);
    if (received == -1)
    continue;

    buf[received] = 0;
    if (strcmp(buf, name) == 0)
    sendto(sock, "bingo", 5, 0, (struct sockaddr *) &addr, addrlen);
    }
    }

    static void *waiton_response(void *arg)
    {
    char *name = (char *) arg;

    while (1) {
    char buf[BUFSIZ+1];
    struct sockaddr_in addr;
    socklen_t addrlen = sizeof(addr);
    int received;

    received = recvfrom(sock, buf, sizeof(buf)-1, 0,
    (struct sockaddr *) &addr, &addrlen);
    if (received == -1)
    continue;
    buf[received] = 0;
    if (strcmp(buf, "bingo") == 0) {
    printf("Got. %s's address is %s.\n",
    name, inet_ntoa(addr.sin_addr));
    exit(0);
    }
    }

    return NULL;
    }

    static void client(const char *name)
    {
    int bcast = 1;
    pthread_t tid;
    pthread_attr_t attr;
    struct sockaddr_in addr;
    int i;

    setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &bcast, sizeof(bcast));

    pthread_attr_init(&attr);
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);

    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = 0xffffffff;
    addr.sin_port = htons(PORT);

    for (i = 0; i < 6; i++) {
    printf("Searching...\n");

    sendto(sock, name, strlen(name), 0,
    (struct sockaddr *) &addr, sizeof(addr));
    if (i == 0)
    pthread_create(&tid, &attr, waiton_response, (void *) name);
    sleep(5);
    }

    printf("Cannot find the machine.\n");
    pthread_attr_destroy(&attr);
    }

    int main(int argc, char **argv)
    {
    progname = argv[0];
    sock = udp_socket();

    if (argc != 3)
    usage();
    if (strcmp(argv[1], "-s") == 0)
    server(argv[2]);
    else if (strcmp(argv[1], "-c") == 0)
    client(argv[2]);
    else
    usage();

    return 0;
    }