Unable to publish base64 code to websocket

1

I tried using ESP32-cam to take pictures and encode them as base 64 but when I used the client.publish(MQTT_LDP_TOPIC, base64Image.c_str()) function to publish, the strings were too long and undeliverable so I wanted to ask if there was a command line other than client.publish to publish them

2

If you’re facing issues with the MQTT payload size being too large for client.publish() in your ESP32-cam project, there are a few strategies you can consider to work around this limitation:

  1. Chunking: Break the data into smaller chunks and publish them individually. On the receiving end, you’ll need to reassemble these chunks to reconstruct the original data. This method requires additional logic on both the sender and receiver sides.
  2. Store and Retrieve: Instead of publishing the entire base64-encoded image, you can store the image on a server or cloud storage and send only the link or identifier via MQTT. The recipient can then retrieve the image using the provided link.
  3. Use a Different Communication Mechanism: If MQTT isn’t suitable for your data size, consider using a different communication mechanism that supports larger payloads. For example, you could use HTTP or another protocol that can handle larger amounts of data.
  4. Compression: Compress the data before sending it. This can be helpful in reducing the payload size. However, keep in mind that the ESP32 has limited resources, so the compression algorithm should be lightweight.

Here’s an example using chunking:

#include <WiFi.h>
#include <PubSubClient.h>

const char* ssid = "your-SSID";
const char* password = "your-PASSWORD";
const char* mqtt_server = "your-MQTT-server";
const char* MQTT_LDP_TOPIC = "your-topic";

WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  // Your setup code here
}

void loop() {
  // Take a picture and encode it as base64
  String base64Image = takeAndEncodePicture();

  // Publish in chunks
  const int chunkSize = 128;  // Adjust the chunk size as needed
  int numChunks = base64Image.length() / chunkSize;

  for (int i = 0; i <= numChunks; i++) {
    int start = i * chunkSize;
    int end = start + chunkSize;
    end = (end > base64Image.length()) ? base64Image.length() : end;

    String chunk = base64Image.substring(start, end);
    String topic = MQTT_LDP_TOPIC + "/chunk/" + String(i);

    client.publish(topic.c_str(), chunk.c_str());

    // Add delay if needed
    delay(100);
  }
}

// Rest of your code here

On the receiving end, you would need to subscribe to the appropriate topic and reassemble the chunks to reconstruct the original base64-encoded image.

Remember to adapt the code to fit your specific requirements and adjust the chunk size based on your network conditions and the size of your base64-encoded images.