Nearby API - queuing of payloads

Question

I have an use case where I am sending control data from AndroidThings device to an Android mobile phone - it is periodal reading of voltage 10 times a second, so every 100 millis. But since this is Nearby API feature - concering sending payloads:

Senders use the sendPayload() method to send a Payload. This method can be invoked multiple times, but since we guarantee in-order delivery, the second Payload onwards will be queued for sending until the first Payload is done.

What happens in reality in my case is, based on the the fact that transmission speed varies, I am getting readings on the phone with delay that is increasing, simply queue gets bigger and bigger.

Any ideas how to overcome this ? Basically I don't need in-order delivery. My first idea is to have some sort of confirmation of payload delivery and only after the confirmation of receipt the second payload should be sent to recipient.

Thanks for ideas

UPDATE:

STREAM type of payload is a perferct solution. If the InputStream transfers more than one set of readings (reading inlcude voltage, maxvoltage etc. altogether 32 bytes of data) then I use the skip method to skip to the very last readings.

Answer 1

For your use-case, I would recommend using a STREAM Payload , and then you can keep streaming your control data over that single Payload -- this is exactly one of the use-cases for which we created STREAM. :)

Answer 2

Yup, your first idea sounds like the right thing to do. There's no way to turn off in-order delivery of payloads inside Nearby Connections, so you'll have to handle dropping payloads yourself.

I would build a class that caches the 'most recent voltage'. As you get new readings, this value will overwrite itself each time.

private volatile Long mostRecentVoltage;

public void updateVoltage(long voltage) {
  if (mostRecentVoltage != null) {
    Log.d(TAG, String.format("Dropping voltage %d due to poor network latency", mostRecentVoltage));
  }
  mostRecentVoltage = voltage;
}

Then add another piece of logic that'll grab the cached value every time the previous payload was successfully sent.

@Nullable
public Long getVoltage() {
  try {
    return mostRecentVoltage;
  } finally {
    mostRecentVoltage = null;
  }
}