Firmware, MQTT Broker Dangered To be overfload with messages published.

[Yhya99]

Describe the bug
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Short Summary of the expected behavior:
Short Summary of the buggy behavior:

the Broker can be easly OverFloaded

To Reproduce
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2. Click on '....'
3. Scroll down to '....'
4. See error
   making the client.loop(); calling every second using millis()

Expected behavior
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Hardware description
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Additional context
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Referencing from GPAD_API.ino File

#if defined HMWK || defined KRAKE
  client.loop();
  publishOnLineMsg();
  wink(); // The builtin LED
#endif

Referencing code from the library PubSubClient.cpp

boolean PubSubClient::loop() {
    if (connected()) {
        unsigned long t = millis();
        if ((t - lastInActivity > this->keepAlive*1000UL) || (t - lastOutActivity > this->keepAlive*1000UL)) {
            if (pingOutstanding) {
                this->_state = MQTT_CONNECTION_TIMEOUT;
                _client->stop();
                return false;
            } else {
                this->buffer[0] = MQTTPINGREQ;
                this->buffer[1] = 0;
                _client->write(this->buffer,2);
                lastOutActivity = t;
                lastInActivity = t;
                pingOutstanding = true;
            }
        }
        if (_client->available()) {
            uint8_t llen;
            uint16_t len = readPacket(&llen);
            uint16_t msgId = 0;
            uint8_t *payload;
            if (len > 0) {
                lastInActivity = t;
                uint8_t type = this->buffer[0]&0xF0;
                if (type == MQTTPUBLISH) {
                    if (callback) {
                        uint16_t tl = (this->buffer[llen+1]<<8)+this->buffer[llen+2]; /* topic length in bytes */
                        memmove(this->buffer+llen+2,this->buffer+llen+3,tl); /* move topic inside buffer 1 byte to front */
                        this->buffer[llen+2+tl] = 0; /* end the topic as a 'C' string with \x00 */
                        char *topic = (char*) this->buffer+llen+2;
                        // msgId only present for QOS>0
                        if ((this->buffer[0]&0x06) == MQTTQOS1) {
                            msgId = (this->buffer[llen+3+tl]<<8)+this->buffer[llen+3+tl+1];
                            payload = this->buffer+llen+3+tl+2;
                            callback(topic,payload,len-llen-3-tl-2);

                            this->buffer[0] = MQTTPUBACK;
                            this->buffer[1] = 2;
                            this->buffer[2] = (msgId >> 8);
                            this->buffer[3] = (msgId & 0xFF);
                            _client->write(this->buffer,4);
                            lastOutActivity = t;

                        } else {
                            payload = this->buffer+llen+3+tl;
                            callback(topic,payload,len-llen-3-tl);
                        }
                    }
                } else if (type == MQTTPINGREQ) {
                    this->buffer[0] = MQTTPINGRESP;
                    this->buffer[1] = 0;
                    _client->write(this->buffer,2);
                } else if (type == MQTTPINGRESP) {
                    pingOutstanding = false;
                }
            } else if (!connected()) {
                // readPacket has closed the connection
                return false;
            }
        }
        return true;
    }
    return false;
}

[ForrestErickson]

The "Referencing code from the library PubSubClient.cpp" has some interesting features.

It checks several variables about which to learn and understand more

1. pingOutstanding
2. a buffer type, to be MQTTPUBLISH
3. Quality of Service for be MQTTQOS1

Reading the source code of the library PubSubClient will be of help.