How to publish and subscribe to MQTT broker through GSM Module in Arduino/ESP8266? - arduino

Question

I am currently working in a project where I have to publish and possibly subscribe to MQTT topic over GSM network (I am using ESP8266 and Ai Thinker A6 GSM Module). So far I am able to publish message to the broker once using MQTT Example code from TinyGSM library,where they pass the GPRS client instance to Pubsub Client class, but when I add a code in loop to publish message continuously every n seconds. The message is published only once or twice and then freezes.
I doubt the mqttclient.loop() function in the void loop(). But, I am just wondering is there any other library which is completely tested, because the TinyGSM developer itself has mentioned this code is not tested in github.
The example code with mqtt publish in loop
// Select your modem:
#define TINY_GSM_MODEM_SIM800
// #define TINY_GSM_MODEM_SIM808
// #define TINY_GSM_MODEM_SIM868
// #define TINY_GSM_MODEM_SIM900
// #define TINY_GSM_MODEM_SIM7000
// #define TINY_GSM_MODEM_SIM5360
// #define TINY_GSM_MODEM_SIM7600
// #define TINY_GSM_MODEM_UBLOX
// #define TINY_GSM_MODEM_SARAR4
// #define TINY_GSM_MODEM_M95
// #define TINY_GSM_MODEM_BG96
// #define TINY_GSM_MODEM_A6
// #define TINY_GSM_MODEM_A7
// #define TINY_GSM_MODEM_M590
// #define TINY_GSM_MODEM_MC60
// #define TINY_GSM_MODEM_MC60E
// #define TINY_GSM_MODEM_ESP8266
// #define TINY_GSM_MODEM_XBEE
// #define TINY_GSM_MODEM_SEQUANS_MONARCH
// Set serial for debug console (to the Serial Monitor, default speed 115200)
#define SerialMon Serial
// Set serial for AT commands (to the module)
// Use Hardware Serial on Mega, Leonardo, Micro
#define SerialAT Serial1
// or Software Serial on Uno, Nano
//#include <SoftwareSerial.h>
//SoftwareSerial SerialAT(2, 3); // RX, TX
// See all AT commands, if wanted
// #define DUMP_AT_COMMANDS
// Define the serial console for debug prints, if needed
#define TINY_GSM_DEBUG SerialMon
// Range to attempt to autobaud
#define GSM_AUTOBAUD_MIN 9600
#define GSM_AUTOBAUD_MAX 115200
// Add a reception delay - may be needed for a fast processor at a slow baud rate
// #define TINY_GSM_YIELD() { delay(2); }
// Define how you're planning to connect to the internet
#define TINY_GSM_USE_GPRS true
#define TINY_GSM_USE_WIFI false
// set GSM PIN, if any
#define GSM_PIN ""
// Your GPRS credentials, if any
const char apn[] = "YourAPN";
const char gprsUser[] = "";
const char gprsPass[] = "";
// Your WiFi connection credentials, if applicable
const char wifiSSID[] = "YourSSID";
const char wifiPass[] = "YourWiFiPass";
// MQTT details
const char* broker = "broker.hivemq.com";
const char* topicLed = "GsmClientTest/led";
const char* topicInit = "GsmClientTest/init";
const char* topicLedStatus = "GsmClientTest/ledStatus";
#include <TinyGsmClient.h>
#include <PubSubClient.h>
// Just in case someone defined the wrong thing..
#if TINY_GSM_USE_GPRS && not defined TINY_GSM_MODEM_HAS_GPRS
#undef TINY_GSM_USE_GPRS
#undef TINY_GSM_USE_WIFI
#define TINY_GSM_USE_GPRS false
#define TINY_GSM_USE_WIFI true
#endif
#if TINY_GSM_USE_WIFI && not defined TINY_GSM_MODEM_HAS_WIFI
#undef TINY_GSM_USE_GPRS
#undef TINY_GSM_USE_WIFI
#define TINY_GSM_USE_GPRS true
#define TINY_GSM_USE_WIFI false
#endif
#ifdef DUMP_AT_COMMANDS
#include <StreamDebugger.h>
StreamDebugger debugger(SerialAT, SerialMon);
TinyGsm modem(debugger);
#else
TinyGsm modem(SerialAT);
#endif
TinyGsmClient client(modem);
PubSubClient mqtt(client);
#define LED_PIN 13
int ledStatus = LOW;
uint32_t lastReconnectAttempt = 0;
void mqttCallback(char* topic, byte* payload, unsigned int len) {
SerialMon.print("Message arrived [");
SerialMon.print(topic);
SerialMon.print("]: ");
SerialMon.write(payload, len);
SerialMon.println();
// Only proceed if incoming message's topic matches
if (String(topic) == topicLed) {
ledStatus = !ledStatus;
digitalWrite(LED_PIN, ledStatus);
mqtt.publish(topicLedStatus, ledStatus ? "1" : "0");
}
}
boolean mqttConnect() {
SerialMon.print("Connecting to ");
SerialMon.print(broker);
// Connect to MQTT Broker
boolean status = mqtt.connect("GsmClientTest");
// Or, if you want to authenticate MQTT:
//boolean status = mqtt.connect("GsmClientName", "mqtt_user", "mqtt_pass");
if (status == false) {
SerialMon.println(" fail");
return false;
}
SerialMon.println(" success");
mqtt.publish(topicInit, "GsmClientTest started");
mqtt.subscribe(topicLed);
return mqtt.connected();
}
void setup() {
// Set console baud rate
SerialMon.begin(115200);
delay(10);
pinMode(LED_PIN, OUTPUT);
// !!!!!!!!!!!
// Set your reset, enable, power pins here
// !!!!!!!!!!!
SerialMon.println("Wait...");
// Set GSM module baud rate
// TinyGsmAutoBaud(SerialAT,GSM_AUTOBAUD_MIN,GSM_AUTOBAUD_MAX);
SerialAT.begin(9600);
delay(3000);
// Restart takes quite some time
// To skip it, call init() instead of restart()
SerialMon.println("Initializing modem...");
modem.restart();
// modem.init();
String modemInfo = modem.getModemInfo();
SerialMon.print("Modem Info: ");
SerialMon.println(modemInfo);
#if TINY_GSM_USE_GPRS
// Unlock your SIM card with a PIN if needed
if ( GSM_PIN && modem.getSimStatus() != 3 ) {
modem.simUnlock(GSM_PIN);
}
#endif
#if TINY_GSM_USE_WIFI
// Wifi connection parameters must be set before waiting for the network
SerialMon.print(F("Setting SSID/password..."));
if (!modem.networkConnect(wifiSSID, wifiPass)) {
SerialMon.println(" fail");
delay(10000);
return;
}
SerialMon.println(" success");
#endif
#if TINY_GSM_USE_GPRS && defined TINY_GSM_MODEM_XBEE
// The XBee must run the gprsConnect function BEFORE waiting for network!
modem.gprsConnect(apn, gprsUser, gprsPass);
#endif
SerialMon.print("Waiting for network...");
if (!modem.waitForNetwork()) {
SerialMon.println(" fail");
delay(10000);
return;
}
SerialMon.println(" success");
if (modem.isNetworkConnected()) {
SerialMon.println("Network connected");
}
#if TINY_GSM_USE_GPRS
// GPRS connection parameters are usually set after network registration
SerialMon.print(F("Connecting to "));
SerialMon.print(apn);
if (!modem.gprsConnect(apn, gprsUser, gprsPass)) {
SerialMon.println(" fail");
delay(10000);
return;
}
SerialMon.println(" success");
if (modem.isGprsConnected()) {
SerialMon.println("GPRS connected");
}
#endif
// MQTT Broker setup
mqtt.setServer(broker, 1883);
mqtt.setCallback(mqttCallback);
}
void loop() {
if (!mqtt.connected()) {
SerialMon.println("=== MQTT NOT CONNECTED ===");
// Reconnect every 10 seconds
uint32_t t = millis();
if (t - lastReconnectAttempt > 10000L) {
lastReconnectAttempt = t;
if (mqttConnect()) {
lastReconnectAttempt = 0;
}
}
delay(100);
return;
}
else
{
mqtt.publish("Topic/test","Hi");
delay(1000);
}
mqtt.loop();
}