send_bytes.go

package main

import (
	"encoding/binary"
	"encoding/hex"
	"net"
	"time"

	"github.com/Sirupsen/logrus"
)

// Send sends packet to dest and gets back one reply from the bulb
// Note that the way it's implemented means it's possible it'll get multiple replies
// (i.e. ack and a response if those are both asked for in the request)
// and only log the first reply
func Send(dest string, packet []byte) error {
	log := logrus.WithField("from", "clientUDP")
	// Initializes the UDP cient
	addr, err := net.ResolveUDPAddr("udp", dest)
	if err != nil {
		return err
	}

	conn, err := net.DialUDP("udp", nil, addr)
	defer conn.Close()
	if err != nil {
		return err
	}

	log.Infof("Sending packet to %s", addr.String())
	// Sends the UDP packet
	_, err = conn.Write(packet)
	if err != nil {
		return err
	}
	// Reads the response
	var n int
	conn.SetReadDeadline(time.Now().Add(2 * time.Second))
	p := make([]byte, 2048)
	n, err = conn.Read(p)
	if err != nil {
		return err
	}
	size := binary.LittleEndian.Uint16(p[0:2])
	reply := hex.EncodeToString(p[0:size])

	log.WithFields(logrus.Fields{
		"response": reply,
		"length":   n,
	}).Info("packet received")

	return nil
}

func main() {
	// These bytes only have length 44, but we need length 100
	// bts, err := hex.DecodeString("2c000034000000000000000000000000000000000000111000000000000000003a0000000123456789abcdef")

	// These bytes are correct
	bts, err := hex.DecodeString("6400001492a3e0600000000000000000000000000000010100000000000000003a00000031323334353637383961626364656600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000")
	if err != nil {
		logrus.Fatal(err)
	}
	err = Send("192.168.0.4:56700", bts)
	if err != nil {
		logrus.Fatal(err)
	}
}