muti threaded broadcast

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <net/if.h>

#include <ifaddrs.h>

#include <string.h>

#include <stdio.h>

#include <errno.h>

#define kPortNumber 1234

#define kBufferSize 1024

#define kMaxSockets 16

int transmit(char * data, int length) {

  int sock_fds[kMaxSockets];

 

  struct ifaddrs *addrs;

  if ( getifaddrs(&addrs) < 0 ) {

    // Error occurred

    return 0;

  }

 

  // Loop through interfaces, selecting those AF_INET devices that support broadcast, but aren't loopback or point-to-point

  const struct ifaddrs *cursor = addrs;

  struct sockaddr_in addr;

  int number_sockets = 0;

 

  while ( cursor != NULL && number_sockets < kMaxSockets ) {

    if ( cursor->ifa_addr->sa_family == AF_INET

            && !(cursor->ifa_flags & IFF_LOOPBACK)

            && !(cursor->ifa_flags & IFF_POINTOPOINT)

            &&  (cursor->ifa_flags & IFF_BROADCAST) ) {

      // Create socket

      sock_fds[number_sockets] = socket(AF_INET, SOCK_DGRAM, 0);

      if ( sock_fds[number_sockets] == -1 ) {

        // Error occurred

        return 0;

      }

     

      // Create address from which we want to send, and bind it

      memset(&addr, 0, sizeof(addr));

      addr.sin_family = AF_INET;

      addr.sin_addr = ((struct sockaddr_in *)cursor->ifa_addr)->sin_addr;

      addr.sin_port = 0;

     

      if ( bind(sock_fds[number_sockets], (struct sockaddr*)&addr, sizeof(addr)) < 0 ) {

        // Error occurred

        return 0;

      }

     

      // Enable broadcast

      int flag = 1;

      if ( setsockopt(sock_fds[number_sockets], SOL_SOCKET, SO_BROADCAST, &flag, sizeof(flag)) != 0 ) {

        // Error occurred

        return 0;

      }

     

      number_sockets++;

    }

    cursor = cursor->ifa_next;

  }

 

  // Initialise broadcast address

  memset(&addr, 0, sizeof(addr));

  addr.sin_family = AF_INET;

  addr.sin_addr.s_addr = INADDR_BROADCAST;

  addr.sin_port = htons(kPortNumber);

 

  // Send through each interface

  int i;

  for ( i=0; i<number_sockets; i++ ) {

    if ( sendto(sock_fds[i], data, length, 0, (struct sockaddr*)&addr, sizeof(addr)) < 0 ) {

      // Error occurred

      return 0;

    }

  }

 

  return 1;

}

int receive() {

 

  // Create socket

  int sock_fd = socket(AF_INET, SOCK_DGRAM, 0);

  if ( sock_fd == -1 ) {

    // Error occurred

    return 0;

  }

 

  // Create address from which we want to receive, and bind it

  struct sockaddr_in addr;

  memset(&addr, 0, sizeof(addr));

  addr.sin_family = AF_INET;

  addr.sin_addr.s_addr = INADDR_ANY;

  addr.sin_port = htons(kPortNumber);

  if ( bind(sock_fd, (struct sockaddr*)&addr, sizeof(addr)) < 0 ) {

    // Error occurred

    return 0;

  }

 

  char buffer[kBufferSize];

  int addr_len = sizeof(addr);

 

  while ( 1 ) {

   

    // Receive a message, waiting if there's nothing there yet

    int bytes_received = recvfrom(sock_fd, buffer, kBufferSize, 0, (struct sockaddr*)&addr, &addr_len);

    if ( bytes_received < 0 ) {

       // Error occurred

       return 0;

    }

   

    // Now we have bytes_received bytes of data in buffer. Print it!

    fwrite(buffer, sizeof(char), bytes_received, stdout);

    printf("\n");

  } 

}

int main(int argc, char** argv) {

  if ( argc < 2 ) {

    // No argument: Just listen

    printf("Listening...\n");

    if ( !receive() ) {

      printf("Error occurred: %s\n", strerror(errno));

      return 1;

    }

    return 0;

  }

  // Argument provided: Transmit this

  if ( transmit(argv[1], strlen(argv[1])) ) {

    printf("\"%s\" transmitted.\n", argv[1]);

  } else {

    printf("Error occurred: %s\n", strerror(errno));

    return 1;

  }

 

  return 0;

}