espat: implement MQTT subscribe functionality via blocking select/channels.

also refactor response processing for greater speed and efficiency.

Signed-off-by: Ron Evans <ron@hybridgroup.com>

examples/espat/mqttclient/main.go

@@ -25,8 +25,9 @@ const ssid = "YOURSSID"
 const pass = "YOURPASS"
 
 // IP address of the MQTT broker to use. Replace with your own info.
-//const server = "tcp://test.mosquitto.org:1883"
-const server = "ssl://test.mosquitto.org:8883"
+const server = "tcp://test.mosquitto.org:1883"
+
+//const server = "ssl://test.mosquitto.org:8883"
 
 // these are the default pins for the Arduino Nano33 IoT.
 // change these to connect to a different UART or pins for the ESP8266/ESP32
@@ -66,7 +67,7 @@ func main() {
 	opts := mqtt.NewClientOptions(adaptor)
 	opts.AddBroker(server).SetClientID("tinygo-client-" + randomString(10))
 
-	println("Connectng to MQTT...")
+	println("Connecting to MQTT broker at", server)
 	cl := mqtt.NewClient(opts)
 	if token := cl.Connect(); token.Wait() && token.Error() != nil {
 		failMessage(token.Error().Error())
@@ -105,13 +106,18 @@ func connectToESP() bool {
 
 // connect to access point
 func connectToAP() {
-	println("Connecting to wifi network...")
+	println("Connecting to wifi network '" + ssid + "'")
 
 	adaptor.SetWifiMode(espat.WifiModeClient)
 	adaptor.ConnectToAP(ssid, pass, 10)
 
 	println("Connected.")
-	println(adaptor.GetClientIP())
+	ip, err := adaptor.GetClientIP()
+	if err != nil {
+		failMessage(err.Error())
+	}
+
+	println(ip)
 }
 
 // Returns an int >= min, < max