PubSub_Troubleshooting

If your data payload coming to or from the device via MQTT PubSUB  isn't coming through, it may be your sprintf char buffer
is too large (exceeds 128 chars), issue is discussed here:  https://github.com/knolleary/pubsubclient/issues/110

To view your current buffer size; example below:

//------------------------------------------
int bufferSizeTest = snprintf(fakeData, sizeof(fakeData), "{\"uptime\":%lu,\"temp\":%d,\"humid\":%d,\"lattitude\":%2.7f,\"longitude\":%3.7f}", millis() / 1000, t, h, latt, lon );

Serial.println('\n');
Serial.println(bufferSizeTest);
Serial.println('\n');
//-------------------------------------------


to fix this problem see below:

Arduino-->libraries-->PubSub folder-->src-->PubSubClient.h

change-->

// MQTT_MAX_PACKET_SIZE : Maximum packet size
#ifndef MQTT_MAX_PACKET_SIZE
#define MQTT_MAX_PACKET_SIZE 128
#endif


to-->

// MQTT_MAX_PACKET_SIZE : Maximum packet size
#ifndef MQTT_MAX_PACKET_SIZE
#define MQTT_MAX_PACKET_SIZE 512
#endif