Custom backend

If you already store data elsewhere, such as a hospital system, a company cloud or a web API, CARP can send measurements there instead.

Forward each measurement

client.measurements (see the quickstart) emits every measurement as soon as it is collected. You can post each one to your server as JSON.

This is a sketch of the approach, not production code. You need a server address that accepts the data, and usually some form of authentication.

flutter pub add http

// At the top of lib/main.dart:
import 'dart:convert';
import 'package:http/http.dart' as http;

// In _startSensing(), after client.resume():
client.measurements.listen((measurement) {
  http.post(
    Uri.parse('https://my-server.example.com/data'),
    headers: {'Content-Type': 'application/json'},
    body: jsonEncode(measurement),
  );
});

Each request body is one measurement:

{
  "sensorStartTime": 1790603452877534,
  "data": {
    "__type": "dk.cachet.carp.stepevent",
    "steps": 4213
  }
}

Use a data manager

For a study, write a data manager: a class that CARP calls for every measurement. In it you can buffer data, retry when the network is back, and batch uploads. A data manager plugs into CARP exactly like the built-in on-device and CAWS options, so the protocol's data endpoint simply points to your server.

See Extending CAMS: adding a new data manager for a step-by-step guide.