flutter_p2p

A Wi-Fi Direct Plugin for Flutter.

This plugin is in alpha and only supports android at the moment.

Getting Started

Required permissions

Put this into your AndroidManifest.xml

<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"/>
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>

Request permission

In order to scan for devices and connect to devices you need to ask for the location Permission

Future<bool> _checkPermission() async {
  if (!await FlutterP2p.isLocationPermissionGranted()) {
    await FlutterP2p.requestLocationPermission();
    return false;
  }
  return true;
}

Register / unregister from WiFi events

To receive notifications for connection changes or device changes (peers discovered etc.) you have to subscribe to the wifiEvents and register the plugin to the native events.

class _MyAppState extends State<MyApp> with WidgetsBindingObserver {
  @override
  void initState() {
    super.initState();
    _register();
    WidgetsBinding.instance.addObserver(this);
  }

  @override
  void dispose() {
    WidgetsBinding.instance.removeObserver(this);
    super.dispose();
  }

  @override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    // Stop handling events when the app doesn't run to prevent battery draining

    if (state == AppLifecycleState.resumed) {
      _register();
    } else if (state == AppLifecycleState.paused) {
      _unregister();
    }
  }

  List<StreamSubscription> _subscriptions = [];

  void _register() async {
    if (!await _checkPermission()) {
      return;
    }
    _subscriptions.add(FlutterP2p.wifiEvents.stateChange.listen((change) {
      // Handle wifi state change
    }));

    _subscriptions.add(FlutterP2p.wifiEvents.connectionChange.listen((change) {
      // Handle changes of the connection
    }));

    _subscriptions.add(FlutterP2p.wifiEvents.thisDeviceChange.listen((change) {
      // Handle changes of this device
    }));

    _subscriptions.add(FlutterP2p.wifiEvents.peersChange.listen((change) {
      // Handle discovered peers
    }));

    _subscriptions.add(FlutterP2p.wifiEvents.discoveryChange.listen((change) {
      // Handle discovery state changes
    }));

    FlutterP2p.register();  // Register to the native events which are send to the streams above
  }

  void _unregister() {
    _subscriptions.forEach((subscription) => subscription.cancel()); // Cancel subscriptions
    FlutterP2p.unregister(); // Unregister from native events
  }
}

Discover devices

After you subscribed to the events you only need to call the FlutterP2p.discoverDevices() method.

List<WifiP2pDevice> _peers = [];

void _register() async {

  /// ...

  _subscriptions.add(FlutterP2p.wifiEvents.peersChange.listen((change) {
    setState(() {
      _peers = change.devices;
    });
  }));

  /// ...
}

void _discover() {
  FlutterP2p.discoverDevices();
}

Connect to a device

Call FlutterP2p.connect(device); and listen to the FlutterP2p.wifiEvents.connectionChange

 bool _isConnected = false;
 bool _isHost = false;
 String _deviceAddress = "";

 void _register() async {
    // ...

    _subscriptions.add(FlutterP2p.wifiEvents.connectionChange.listen((change) {
      setState(() {
        _isConnected = change.networkInfo.isConnected;
        _isHost = change.wifiP2pInfo.isGroupOwner;
        _deviceAddress = change.wifiP2pInfo.groupOwnerAddress;
      });
    }));

    // ...
  }

Disconnect from current P2P group

Call FlutterP2p.removeGroup()

 void _disconnect() async {
   FlutterP2p.removeGroup();
 }

Transferring data between devices

After you are connected to a device you can transfer data async in both directions (client -> host, host -> client).

On the host:

  // Open a port and create a socket

  P2pSocket _socket;
  void _openPortAndAccept(int port) async {
    var socket = await FlutterP2p.openHostPort(port);
    setState(() {
      _socket = socket;
    });

    var buffer = "";
    socket.inputStream.listen((data) {
      var msg = String.fromCharCodes(data.data);
      buffer += msg;

      if (data.dataAvailable == 0) {
        _showSnackBar("Data Received: $buffer");
        buffer = "";
      }
    });

    // Write data to the client using the _socket.write(UInt8List) or `_socket.writeString("Hello")` method


    print("_openPort done");

    // accept a connection on the created socket
    await FlutterP2p.acceptPort(port);
    print("_accept done");
  }

On the client:

  // Connect to the port and create a socket

  P2pSocket _socket;
  _connectToPort(int port) async {
    var socket = await FlutterP2p.connectToHost(
      _deviceAddress, // see above `Connect to a device`
      port,
      timeout: 100000, // timeout in milliseconds (default 500)
    );

    setState(() {
      _socket = socket;
    });

    var buffer = "";
    socket.inputStream.listen((data) {
      var msg = String.fromCharCodes(data.data);
      buffer += msg;

      if (data.dataAvailable == 0) {
        _showSnackBar("Received from host: $buffer");
        buffer = "";
      }
    });

    // Write data to the host using the _socket.write(UInt8List) or `_socket.writeString("Hello")` method

    print("_connectToPort done");
  }