Server accidentally throwing error: Invalid WebSocket frame: RSV2 and RSV3 must be clear

[taizhouchen]

I am using sendBIN() to send audio data steam from a ESP32 client to a nodejs server. The audio data is captured through a i2s microphone. I create a xTask to keep watching on the audio buffer and send until it reaches a certain length (chunk size was set to 2000 byte in my case). But the server accidentally throwing error "Invalid WebSocket frame: RSV2 and RSV3 must be clear".

Here is the code of my xTask:

void AudioRecorder::_processAudioBuffTask(void* self)
{
        AudioRecorder* recorder = static_cast<AudioRecorder*>(self);
        uint8_t* chunk = (uint8_t*)malloc(SEND_CHUNK_SIZE);
        if (chunk == NULL) {
            recorder->print("Failed to allocate memory for chunk");
            vTaskDelete(NULL); // Exit task if memory allocation fails
            return;
        }
        while (true) {
            Serial.println("Process Task running...");
            if (recorder->_audio_buff.size() > SEND_CHUNK_SIZE && recorder->_audioDataComingCallback) {
                for (int i = 0; i < SEND_CHUNK_SIZE; i++) {
                    chunk[i] = recorder->_audio_buff.shift();
                }
                recorder->_audioDataComingCallback(chunk, SEND_CHUNK_SIZE);    //Send the data
            }
            // Handle remaining data in shutdown mode
            if(recorder->shutdownInProgress && recorder->_audio_buff.size() <= SEND_CHUNK_SIZE && recorder->_audioDataComingCallback){
                uint16_t size_left = recorder->_audio_buff.size();
                chunk = (uint8_t*)realloc(chunk, size_left);
                if (chunk == NULL) {
                    recorder->print("Failed to allocate memory for chunk");
                    break;
                }
                // uint8_t chunk[size_left]; // Adjust chunk size to match remaining buffer size
                for (size_t i = 0; i < size_left; i++) {
                    chunk[i] = recorder->_audio_buff.shift();
                }
                recorder->_audioDataComingCallback(chunk, size_left);
                break;
            }
            vTaskDelay(40 / portTICK_PERIOD_MS); // Adjust as needed
        }
        recorder->shutdownInProgress = false;
        free(chunk);
        recorder->print("Process Task Completed");
        if(recorder->_stopProcessTaskCallback != NULL) 
            recorder->_stopProcessTaskCallback();  // Send ending audio signal to the server
        recorder->_processAudioBuffTaskHandle = NULL;
        vTaskDelete(NULL); // Delete task when done
}

where the _audioDataComingCallback function simple:

void sendAudioChunk(uint8_t* data, size_t size) {
      if(webSocketsClient.isConnected()){
        webSocketsClient.sendBIN(data, size);
        webSocketsClient.loop();
      }else{
        Serial.println("Web socket server not connected.");
        stopRecording();
      }
    }

I doubt if this is caused by the call of webSocketsClient.loop() since it is called in the main thread loop. I have add webSocketsClient.loop() right after I call sendBIN(), but it won't solved the problem. Can anyone help me on that?