Receive Message - IoT SDK

To receive application messages sent by other participants, register a handler with setDataMessageHandler(). Once a handler is set, the SDK delivers every incoming text or binary message to it. Without a handler, incoming messages are dropped.

Messages are sent by the other participant using sendMessage(). See Send Message.

setDataMessageHandler()

• The setDataMessageHandler() function registers (or clears, by passing NULL) the callback invoked for each application message received from another participant.
• Register the handler right after init(), before your start* calls, so early messages are not missed.

This function takes one parameter:

• cb: a function pointer of type data_message_cb_t, or NULL to clear a previously registered handler.

The callback has the following signature:

typedef void (*data_message_cb_t)(const uint8_t* data, size_t len,
                                  int is_binary, uint16_t sid);

• data / len: the complete message and its length. Message reassembly is handled for you.
• is_binary: 1 for a WebRTC binary message, 0 for a UTF-8 text message.
• sid: the stream id the message arrived on.

Example

#include "videosdk.h"
#include "esp_log.h"

static const char *TAG = "IOT-SDK";

// Called for each application message from another participant.
static void on_data_message(const uint8_t *data, size_t len, int is_binary, uint16_t sid){
  if (is_binary)
    ESP_LOGI(TAG, "msg recv (binary) sid=%u len=%u", (unsigned)sid, (unsigned)len);
  else
    ESP_LOGI(TAG, "msg recv (text) sid=%u: %.*s", (unsigned)sid, (int)len, (const char *)data);
}

void app_main(){
  // ... init(&init_cfg) ...

  // Register the receive handler before starting streams.
  setDataMessageHandler(on_data_message);
}

API Reference

The API references for all the methods utilized in this guide are provided below.

• setDataMessageHandler