LIFX Packet Sending Example

lifx.c

#include "lifx.h"

#include <arpa/inet.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

#include <stdio.h>
#include <string.h>

int main(int argc, char** argv)
{
  int sockaddr_len;
  int status;
  struct sockaddr_in listen_addr, broadcast_addr, recv_addr;
  lifx_header header;

  sockaddr_len = sizeof(struct sockaddr_in);

  memset(&listen_addr, 0, sockaddr_len);
  memset(&broadcast_addr, 0, sockaddr_len);
  memset(&recv_addr, 0, sockaddr_len);

  int client_socket = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
  listen_addr.sin_addr.s_addr = htonl(INADDR_ANY);
  listen_addr.sin_port = htons(0);
  listen_addr.sin_family = AF_INET;

  status = bind(client_socket, (struct sockaddr*)&listen_addr, sockaddr_len);
  printf("Client Bind Status: %d\n", status);

  int yes = 1;
  status = setsockopt(client_socket, SOL_SOCKET, SO_BROADCAST, (const char*)&yes, sizeof(int));
  printf("Setsockopt Status: %d\n", status);

  // Send a packet
  broadcast_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST); // broadcast
  broadcast_addr.sin_port = htons(56700);
  broadcast_addr.sin_family = AF_INET;

  memset(&header, 0, sizeof(lifx_header));
  header.size = sizeof(lifx_header);
  header.origin = 0;
  header.tagged = 1;
  header.addressable = 1;
  header.protocol = 1024;
  header.source = 123;
  header.target[0] = 0;
  header.target[1] = 0;
  header.target[2] = 0;
  header.target[3] = 0;
  header.target[4] = 0;
  header.target[5] = 0;
  header.target[6] = 0;
  header.target[7] = 0;
  header.ack_required = 0;
  header.res_required = 1;
  header.sequence = 100;
  header.type = 2; // GetService

  status = sendto(client_socket, (const char*)&header, sizeof(lifx_header), 0, (struct sockaddr*)&broadcast_addr, sockaddr_len);
  printf("Client Sendto Status: %d\n", status);

  // Receive a packet - should be the broadcast message
  lifx_header recv_header;
  status = recvfrom(client_socket, (char*)&recv_header, sizeof(lifx_header), 0, (struct sockaddr*)&recv_addr, (int*)(&sockaddr_len));
  printf("Server recvfrom: %d\n", status);

  if (status > 0)
  {
    printf("Received message of type %d\n", recv_header.type);
    printf("Sequence is %d\n", recv_header.sequence);
  }

  close(client_socket);

  return 0;
}

lifx.h

#pragma once

#include <stdint.h>

#pragma pack(push, 1)
typedef struct {
  /* frame */
  uint16_t size;
  uint16_t protocol:12;
  uint8_t  addressable:1;
  uint8_t  tagged:1;
  uint8_t  origin:2;
  uint32_t source;
  /* frame address */
  uint8_t  target[8];
  uint8_t  reserved[6];
  uint8_t  res_required:1;
  uint8_t  ack_required:1;
  uint8_t  :6;
  uint8_t  sequence;
  /* protocol header */
  uint64_t :64;
  uint16_t type;
  uint16_t :16;
  /* variable length payload follows */
} lifx_header;
#pragma pack(pop)

Compile with:

gcc lifx.c -o lifx

Run with:

./lifx