Custom MQTT client running on ESP8266 cannot connect to RabbitMQ over MQTT

[shahasab]

I am trying to publish a message to an MQTT broker via RabbitMQ using an ESP8266 module. However, I am facing an issue where the ESP8266 is not able to connect to the MQTT broker. The log indicates a login timeout error.
RabbitMQ Version: 3.12.13
Erlang Version: 26.2.4
MQTT Plugin Version: 3.12.13

[lukebakken]

If you are using TLS, this is probably the issue you are facing:

https://groups.google.com/g/rabbitmq-users/c/VT4GKJVJT7s/m/eV2eHhKZAQAJ

If not, your ESP8266 code has a bug. The person who I helped in that thread sent me ESP8266 hardware, so if you can provide your code, I can investigate this issue (when I have time).

[shahasab]

Hi,
Thank you for the information and the link. I can confirm that I am not using TLS. Given this, it seems likely that there is a bug in my ESP8266 code. Here is my code:

int Send_MQTT_Message(char *mqttTopic, char *mqttMessage)
{
    char RxBuffer1[300];
    memset(RxBuffer1, 0, sizeof(RxBuffer1));

    // Step 1: Connect to MQTT broker
    char strStart[100];
    memset(strStart, 0, sizeof(strStart));
   // snprintf(strStart, sizeof(strStart), "AT+CIPSTART=\"TCP\",\"%s\",%s\r\n", targetIP, targetPort);
    strcat(strStart,"AT+CIPSTART=\"TCP\",\"");
    strcat(strStart,IP);
    strcat(strStart,"\",");
    strcat(strStart,PORT);
    strcat(strStart,"\r\n");
    Print_Data(strStart, USART2);
    if (!Receive_Data1(RxBuffer1, "OK")) {
        Reset_LED(1);  // Error indication
        return 0;  // Return error
    }

    // Step 2: Construct MQTT CONNECT packet with username and password
    uint8_t connectPacket[100];
    int usernameLength = strlen(mqtt_user);
    int passwordLength = strlen(mqtt_pass);
    int clientIdLength = strlen(clientId);
    int variableHeaderLength = 10 + usernameLength + 2 + passwordLength + 2;  // Protocol Name Length (2) + Protocol Name (4) + Protocol Level (1) + Connect Flags (1) + Keep Alive (2) + Username Flag (2) + Password Flag (2)
    int payloadLength = usernameLength + 2 + passwordLength + 2;
    int remainingLength = variableHeaderLength + payloadLength;

    int offset = 0;
    connectPacket[offset++] = 0x10;  // MQTT CONNECT packet type
    connectPacket[offset++] = remainingLength;  // Remaining length

    connectPacket[offset++] = 0x00;  // Protocol Name Length MSB
    connectPacket[offset++] = 0x06;  // Protocol Name Length LSB
    connectPacket[offset++] = 'M';
    connectPacket[offset++] = 'Q';
    connectPacket[offset++] = 'I';
    connectPacket[offset++] = 's';
    connectPacket[offset++] = 'd';
    connectPacket[offset++] = 'p';  // Protocol Name
    connectPacket[offset++] = 0x03;  // Protocol Level
    connectPacket[offset++] = 0xC2;  // Connect Flags (Clean Session + Username + Password)
    connectPacket[offset++] = 0x00;  // Keep Alive MSB
    connectPacket[offset++] = 0x3C;  // Keep Alive LSB (60 seconds)

    connectPacket[offset++] = (clientIdLength >> 8) & 0xFF;  // Client ID Length MSB
    connectPacket[offset++] = clientIdLength & 0xFF;  // Client ID Length LSB
    memcpy(&connectPacket[offset], clientId, clientIdLength);
    offset += clientIdLength;

    connectPacket[offset++] = 0x00;  // Username Length MSB
    connectPacket[offset++] = usernameLength;  // Username Length LSB
    memcpy(&connectPacket[offset], mqtt_user, usernameLength);
    offset += usernameLength;

    connectPacket[offset++] = 0x00;  // Password Length MSB
    connectPacket[offset++] = passwordLength;  // Password Length LSB
    memcpy(&connectPacket[offset],mqtt_pass, passwordLength);
    offset += passwordLength;

    // Step 3: Send CONNECT packet
    char sendCommand[30];
    snprintf(sendCommand, sizeof(sendCommand), "AT+CIPSEND=%d\r\n", offset);
    Print_Data(sendCommand, USART2);

    if (!Receive_Data1(RxBuffer1, ">")) {
        Reset_LED(1);  // Error indication
        return 0;  // Return error
    }
    Print_Data((char *)connectPacket, USART2); // Use Print_Data instead of HAL_UART_Transmit
    if (!Receive_Data1(RxBuffer1, "OK")) {
        Reset_LED(1);  // Error indication
        return 0;  // Return error
    }


    // Step 4: Construct MQTT PUBLISH packet
    uint8_t publishPacket[200];
    int topicLength = strlen(mqttTopic);
    int messageLength = strlen(mqttMessage);
    int publishPacketLen = 2 + topicLength + messageLength + 2;  // Remaining length

    offset = 0;
    publishPacket[offset++] = 0x30;  // MQTT PUBLISH packet type
    publishPacket[offset++] = publishPacketLen;  // Remaining length

    publishPacket[offset++] = 0x00;  // Topic Length MSB
    publishPacket[offset++] = topicLength;  // Topic Length LSB
    memcpy(&publishPacket[offset], mqttTopic, topicLength);
    offset += topicLength;

    memcpy(&publishPacket[offset], mqttMessage, messageLength);
    offset += messageLength;

    // Step 5: Send PUBLISH packet
    snprintf(sendCommand, sizeof(sendCommand), "AT+CIPSEND=%d\r\n", offset);
    Print_Data(sendCommand, USART2);
    if (!Receive_Data1(RxBuffer1, ">")) {
        Reset_LED(1);  // Error indication
       // Print_Data("hello",USART2);
        return 0;  // Return error
    }
    Print_Data((char *)publishPacket, USART2); // Use Print_Data instead of HAL_UART_Transmit
    if (!Receive_Data1(RxBuffer1, "OK")) {
        Reset_LED(1);  // Error indication
        return 0;  // Return error
    }

    Set_LED(2);  // Success indication
    return 1;  // Return success
}

[shahasab]

Hi,
Can anyone please help me solve this problem?

[lukebakken]

There is no need to bump a discussion. People assist you for FREE and will do so if they have the time and interest. Personally, I am busy working on more important items for customers who pay for RabbitMQ support.

You should make your code available in a repository on GitHub rather than pasting it into a comment.

Finally, why in the world are you writing your own MQTT client code when there is already a MQTT client library available for the ESP8266? You should NOT write your own code.

https://www.emqx.com/en/blog/esp8266-connects-to-the-public-mqtt-broker