LIFX Developer Zone

Lights Discovery, all lights send the same port

#1

I’m trying to build a project using the LAN API,
I’ve followed the guide on here: https://lan.developer.lifx.com/docs/workflow-diagrams#discovery trying to discover all the lights on my network.

problem is, the response i’m receiving has all the lights with the same port.

I have 3 lights in my house,
I send a UDP message to 255.255.255.255:56700 as documented,
tagged=1 in the header,
i receive in return 6 message:

UDP State service received:
  service: 1
  port: 56700
UDP State service received:
  service: 1
  port: 56700
UDP State service received:
  service: 5
  port: 56700
UDP State service received:
  service: 5
  port: 56700
UDP State service received:
  service: 1
  port: 56700
UDP State service received:
  service: 5
  port: 56700

service 1 makes sense as the documentation states, I assume service 5 is for future use, but the port is the same on all messages.
how can i address specific bulbs?

Here’s my code:

#include <ESP8266WiFi.h>
#include <SPI.h>        
#include <WiFiUdp.h>

unsigned int localPort = 8888; // Port we listen to
unsigned int lifxPort  = 56700; // Port for talking to LIFX devices

// Remote IP (In this case we broadcast to the entire subnet)
IPAddress broadcast_ip(255, 255, 255, 255);

// LIFX Header structure
#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)

// Device::StateService Payload
#pragma pack(push, 1)
typedef struct {
  uint8_t service;
  uint32_t port;
} lifx_payload_device_state_service;
#pragma pack(pop)

// Payload types
#define LIFX_DEVICE_GET_SERVICE 2
#define LIFX_DEVICE_STATE_SERVICE 3

#define LIFX_INCOMING_PACKET_BUFFER_LEN 300 // Packet buffer size
#define LIFX_SERIAL_LEN 6 // Length in bytes of serial numbers

// An EthernetUDP instance to let us send and receive packets over UDP
WiFiUDP Udp;

// Timing data
unsigned long timeoutInterval = 500;

void setup() {
  // ... Here i Connect to WiFi
  Udp.begin(localPort); // Listen for incoming UDP packets

  GetDevices();
}

void loop() {
  // ... Loop code
}

void GetDevices() {
  lifx_header header;
  
  // Initialise both structures
  memset(&header, 0, sizeof(header));
  
  // Setup the header
  header.size = sizeof(lifx_header); // Size of header + payload
  header.tagged = 1;
  header.addressable = 1;
  header.protocol = 1024;
  header.source = 123;
  header.ack_required = 0;
  header.res_required = 0;
  header.sequence = 100;
  header.type = LIFX_DEVICE_GET_SERVICE;
  
  // Send a packet on startup
  Udp.beginPacket(broadcast_ip, 56700);
  Udp.write((char *) &header, sizeof(lifx_header));
  Udp.endPacket();
  
  unsigned long started = millis();
  while (millis() - started < timeoutInterval) {
    int packetLen = Udp.parsePacket();
    byte packetBuffer[LIFX_INCOMING_PACKET_BUFFER_LEN];
    if (packetLen && packetLen < LIFX_INCOMING_PACKET_BUFFER_LEN) {
      Udp.read(packetBuffer, sizeof(packetBuffer));
      
      if (((lifx_header *)packetBuffer)->type == LIFX_DEVICE_STATE_SERVICE) {
        Serial.println("UDP State service recieved:");
        
        uint8_t service = ((lifx_payload_device_state_service *)(packetBuffer + sizeof(lifx_header)))->service;
        uint32_t port = ((lifx_payload_device_state_service *)(packetBuffer + sizeof(lifx_header)))->port;
        Serial.println("  service: " + String(service));
        Serial.println("  port: " + String(port));

      } else {
        Serial.print("Unexpected Packet type: ");
        Serial.println(((lifx_header *)packetBuffer)->type);
      }
    }
  }
}

am i doing something wrong?

#2

Looks like you are close, but you need to record the IP address of each bulb so you can know where to send the messages. Check the WiFiUdp library for a remoteIP() function to retrieve the IP address for the bulbs when parsing the responses. Hope that helps!

#3

Oh wow, i would have never guessed that, i wish it was more clear in the docs.

So after i get the ip i should send a UDP message directly to this device instead of 255.255.255.255?

thank you!

#4

You got it!

The IP address 255.255.255.255 is a broadcast address meaning the message gets sent to everyone on your network. Once you get the IP address of a LIFX device, you can start to send unicast messages which are delivered to that device only.

Best of luck on your project!

#5

So in that case, what is the purpose of the target field in the header?
and do i need to send it when sending a message directly to a device?

#6

I recommend reading through the header description. It has been a while since I implemented my own controller and had just been looking at my undocumented code lol to respond before lol. https://lan.developer.lifx.com/docs/header-description contains the information you are looking for.

In short though, the target field can be used to target a device based on its MAC address rather than an IP address. But this is dependent on the “flagged” field. I believe the implementation I made ignored the target and used IP unicast only. But my implementation is not very refined and the header description does recommended setting the target. The state-service responses should contain the MAC address of the device.