Add new MQTT client example using natiu-mqtt

Add new MQTT client example using natiu-mqtt

examples/net/mqttclient/natiu/main.go

@@ -0,0 +1,136 @@
+// This example is an MQTT client built with the natiu-mqtt package.  It sends
+// machine.CPUFrequency() readings to the broker every second for 10 seconds.
+//
+// Note: It may be necessary to increase the stack size when using
+// paho.mqtt.golang.  Use the -stack-size=4KB command line option.
+
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"machine"
+	"math/rand"
+	"net"
+	"time"
+
+	mqtt "github.com/soypat/natiu-mqtt"
+)
+
+var (
+	ssid   string
+	pass   string
+	broker string = "test.mosquitto.org:1883"
+	topic  string = "cpu/freq"
+)
+
+func main() {
+	waitSerial()
+
+	if err := netdev.NetConnect(); err != nil {
+		log.Fatal(err)
+	}
+
+	clientId := "tinygo-client-" + randomString(10)
+	fmt.Printf("ClientId: %s\n", clientId)
+
+	// Get a transport for MQTT packets
+	fmt.Printf("Connecting to MQTT broker at %s\n", broker)
+	conn, err := net.Dial("tcp", broker)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer conn.Close()
+
+	// Create new client
+	client := mqtt.NewClient(mqtt.ClientConfig{
+		Decoder: mqtt.DecoderNoAlloc{make([]byte, 1500)},
+		OnPub: func(_ mqtt.Header, _ mqtt.VariablesPublish, r io.Reader) error {
+			message, _ := io.ReadAll(r)
+			fmt.Printf("Message %s received on topic %s\n", string(message), topic)
+			return nil
+		},
+	})
+
+	// Connect client
+	var varconn mqtt.VariablesConnect
+	varconn.SetDefaultMQTT([]byte(clientId))
+	ctx, _ := context.WithTimeout(context.Background(), 10*time.Second)
+	err = client.Connect(ctx, conn, &varconn)
+	if err != nil {
+		log.Fatal("failed to connect: ", err)
+	}
+
+	// Subscribe to topic
+	ctx, _ = context.WithTimeout(context.Background(), 10*time.Second)
+	err = client.Subscribe(ctx, mqtt.VariablesSubscribe{
+		PacketIdentifier: 23,
+		TopicFilters: []mqtt.SubscribeRequest{
+			{TopicFilter: []byte(topic), QoS: mqtt.QoS0},
+		},
+	})
+	if err != nil {
+		log.Fatal("failed to subscribe to", topic, err)
+	}
+	fmt.Printf("Subscribed to topic %s\n", topic)
+
+	// Publish on topic
+	pubFlags, _ := mqtt.NewPublishFlags(mqtt.QoS0, false, false)
+	pubVar := mqtt.VariablesPublish{
+		TopicName: []byte(topic),
+	}
+
+	for i := 0; i < 10; i++ {
+		if !client.IsConnected() {
+			log.Fatal("client disconnected: ", client.Err())
+		}
+
+		freq := float32(machine.CPUFrequency()) / 1000000
+		payload := fmt.Sprintf("%.02fMhz", freq)
+
+		pubVar.PacketIdentifier++
+		err = client.PublishPayload(pubFlags, pubVar, []byte(payload))
+		if err != nil {
+			log.Fatal("error transmitting message: ", err)
+		}
+
+		time.Sleep(time.Second)
+
+		conn.SetReadDeadline(time.Now().Add(10*time.Second))
+		err = client.HandleNext()
+		if err != nil {
+			log.Fatal("handle next: ", err)
+		}
+
+	}
+
+	client.Disconnect(errors.New("disconnected gracefully"))
+
+	for {
+		select {}
+	}
+}
+
+// Returns an int >= min, < max
+func randomInt(min, max int) int {
+	return min + rand.Intn(max-min)
+}
+
+// Generate a random string of A-Z chars with len = l
+func randomString(len int) string {
+	bytes := make([]byte, len)
+	for i := 0; i < len; i++ {
+		bytes[i] = byte(randomInt(65, 90))
+	}
+	return string(bytes)
+}
+
+// Wait for user to open serial console
+func waitSerial() {
+	for !machine.Serial.DTR() {
+		time.Sleep(100 * time.Millisecond)
+	}
+}