Unable to send publish messages from esp8266 to Raspberry (Broker) using MQTT. Getting Socket Error <Random Device Id>, Disconnecting - raspberry-pi

Question

I am trying to send and receive a messages from Raspberry Pi (Broker) to Arduino-ESP8266 (client) using MQTT. What I am trying to achieve is pretty basic for now. The broker sends a start command and the client on receving the message should send back a random number. I am able to read the message sent by the broker but the messages from the client are never sent. Here is the code that I am using
#include <WiFiEsp.h>
#include <WiFiEspClient.h>
#ifndef HAVE_HWSERIAL1
#include "SoftwareSerial.h"
SoftwareSerial Serial1(19, 18); //RX, TX
#endif
#define MQTT_KEEPALIVE 10
#include <PubSubClient.h>
IPAddress server(192, 168, 0, 105);
char ssid[] = "user1956";
char password[] = "******";
int status = WL_IDLE_STATUS; //wifi radio's status
//MQTT
//const char* mqtt_topic = "Rpi_Master";
const char* mqtt_username = "pi";
const char* mqtt_password = "********";
//client Id
const char* clientID = "A_2";
//Variables for numbers
long randNumber1;
String rn1;
char rn1_char[50];
WiFiEspClient wifiClient;
PubSubClient client(wifiClient); //1883 is the listener port for the broker
void setup() {
// Initilize serial for debugging
Serial.begin(115200);
//initilize serial for ESP module
Serial1.begin(115200);
//initilize the ESP module
WiFi.init(&Serial1);
if (WiFi.status() == WL_NO_SHIELD)
{
Serial.println("WiFi shield not present");
while (true);
}
while (status != WL_CONNECTED)
{
Serial.print("Attempting to connect to WPA SSID : ");
Serial.println(ssid);
status = WiFi.begin(ssid, password);
}
Serial.println("You are connected to the network");
client.setServer(server, 1883);
client.setCallback(callback);
//Allow the hardware to sort itself
delay(1500);
randomSeed(50);
}
void callback(char* topic, byte* payload, unsigned int length)
{
Serial.print("Message Received: [");
Serial.print(topic);
Serial.println("]");
Serial.print("Message is:");
String message = (char *)payload;
Serial.println(message);
else if (!strncmp((char *)payload, "B1", length)) //Start code can be changed to any string value in place of 1
{
client.publish("Ad_B", "OK");
generateRandomData();
}
else if (!strncmp((char *)payload, "B2", length)) //Start code can be changed to any string value in place of 1
{
client.publish("Ad_B", "OK");
generateRandomData();
}
}
void loop()
{
if (!client.connected())
{
reconnect();
}
client.loop();
delay(1000);
}
void reconnect()
{
while (!client.connected())
{
Serial.print("Attempting MQTT Connection...");
//Attempt to Connect
if (client.connect(clientID, mqtt_username, mqtt_password))
{
Serial.println("connected");
//Once connected publish an announcement
client.publish("Ad_B", "Ready");
//and resubscribe
client.subscribe("Rpi_Master"); //This name can be changed
}
else
{
Serial.print("failed, rc = ");
Serial.print(client.state());
Serial.println("Trying again in 5 seconds");
//Wait for 5 seconds before retrying
delay(5000);
}
}
}
void generateRandomData(){
randNumber1 = random(0,0); //(14000,15000)
//Serial.println(randNumber1); // print a random number from 0to 299
rn1 = String(randNumber1);
rn1.toCharArray(rn1_char, rn1.length() + 1);
client.publish("LC_B_1", rn1_char);
client.publish("Ad_B", "End");
}
This is the output of the serial monitor that I am receiving:
07:45:42.016 -> [WiFiEsp] Initializing ESP module
07:45:45.430 -> [WiFiEsp] Initilization successful - 1.5.4
07:45:45.430 -> Attempting to connect to WPA SSID : No Free Wifi
07:45:50.464 -> [WiFiEsp] Connected to No Free Wifi
07:45:50.464 -> You are connected to the network
07:45:51.940 -> Attempting MQTT Connection...[WiFiEsp] Connecting to 192.168.0.105
07:45:52.084 -> connected
07:46:31.926 -> Message Received: [Rpi_Master]
07:46:31.926 -> Message is:B2ter
07:46:37.438 -> [WiFiEsp] TIMEOUT: 20
08:20:58.967 -> [WiFiEsp] >>> TIMEOUT >>>
The client is unable to publish any messages. The mosquitto log shows PINGREQ and RINGRESP to a random id and client.publish stops with the following message in the log - Socket Error on Client <Some Random Client Id>, Disconnecting. Attached the screenshot of the log. Is there any way to know what the unknown client is? Please help me to sort this issue. Thanks.

Answer 1

You generateRandom() function blocks (15 seconds) for longer than the keep alive (10 seconds) timeout and this will block the client.loop() function so it will not be able to send keep alive packets.