nearby_connections

An android flutter plugin for the Nearby Connections API Currently supports Bytes and Files.

Transfer Data between multiple connected devices using fully offline peer to peer networking

Table of Content

• Setup
• Work Flow
  • Advertise For connections
  • Discover Advertisers
  • Request Connection
  • Accept Connection
• Sending Data
  • Sending Bytes Payload
  • Sending Files

Setup

Note regarding Location(GPS)

While using this, Location/GPS service must be turned on or devices may disconnect more often, some devices may disconnect immediately.

Set Permissions

Add these to AndroidManifest.xml

<!-- Required for Nearby Connections -->
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:minSdkVersion="29" android:name="android.permission.ACCESS_FINE_LOCATION" />

<!-- For Android 12+ support-->
<uses-permission android:minSdkVersion="31" android:name="android.permission.BLUETOOTH_ADVERTISE" />
<uses-permission android:minSdkVersion="31" android:name="android.permission.BLUETOOTH_CONNECT" />
<uses-permission android:minSdkVersion="31" android:name="android.permission.BLUETOOTH_SCAN" />

<!-- Optional: only required for FILE payloads-->
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

Note: Android 12+ has introduced some new bluetooth permissions - BLUETOOTH_ADVERTISE, BLUETOOTH_CONNECT, BLUETOOTH_SCAN, which need to be handled as well. You may also need to set compileSdkVersion 32 in your build.gradle file.

Request Permissions

Since ACCESS_FINE_LOCATION and READ_EXTERNAL_STORAGE is considered to be dangerous system permissions, in addition to adding them to your manifest, you must request these permissions at runtime.

You can use the permission_handler package to handle all these permissions and the location package to request enabling location

// location permission
await Permission.location.isGranted         // Check
await Permission.location.request()         // Ask

// location enable dialog
await Location.instance.requestService()

// external storage permission
await Permission.storage.isGranted          // Check
await Permission.storage.request()          // Ask

// Bluetooth permissions
bool granted = !(await Future.wait([        // Check
    Permission.bluetooth.isGranted,
    Permission.bluetoothAdvertise.isGranted,
    Permission.bluetoothConnect.isGranted,
    Permission.bluetoothScan.isGranted,
])).any((element) => false);
[                                           // Ask
    Permission.bluetooth,
    Permission.bluetoothAdvertise,
    Permission.bluetoothConnect,
    Permission.bluetoothScan
].request();

Checkout the Example in Repository for more details.

NOTE

Location/GPS service must be turned on or devices may disconnect more often, some devices may disconnect immediately.

Work Flow

The work flow is similar to the Android Nearby Connections library

Advertise for connection

try {
    bool a = await Nearby().startAdvertising(
        userName,
        strategy,
        onConnectionInitiated: (String id,ConnectionInfo info) {
        // Called whenever a discoverer requests connection 
        },
        onConnectionResult: (String id,Status status) {
        // Called when connection is accepted/rejected
        },
        onDisconnected: (String id) {
        // Callled whenever a discoverer disconnects from advertiser
        },
        serviceId: "com.yourdomain.appname", // uniquely identifies your app
    );
} catch (exception) {
    // platform exceptions like unable to start bluetooth or insufficient permissions 
}

Discover Advertisers

try {
    bool a = await Nearby().startDiscovery(
        userName,
        strategy,
        onEndpointFound: (String id,String userName, String serviceId) {
            // called when an advertiser is found
        },
        onEndpointLost: (String id) {
            //called when an advertiser is lost (only if we weren't connected to it )
        },
        serviceId: "com.yourdomain.appname", // uniquely identifies your app
    );
} catch (e) {
    // platform exceptions like unable to start bluetooth or insufficient permissions
}

Stopping Advertising and Discovery

Nearby().stopAdvertising();
Nearby().stopDiscovery();
// endpoints already discovered will still be available to connect
// even after stopping discovery
// You should stop discovery once you have found the intended advertiser
// this will reduce chances for disconnection

Request Connection

// to be called by discover whenever an endpoint is found
// callbacks are similar to those in startAdvertising method
try{ 
    Nearby().requestConnection(
        userName,
        id,
        onConnectionInitiated: (id, info) {
        },
        onConnectionResult: (id, status) {
        },
        onDisconnected: (id) {
        },
    );
}catch(exception){
    // called if request was invalid
}

Accept Connection

Nearby().acceptConnection(
    id,
    onPayLoadRecieved: (endpointId, payload) {
        // called whenever a payload is recieved.
    },
    onPayloadTransferUpdate: (endpointId, payloadTransferUpdate) {
        // gives status of a payload
        // e.g success/failure/in_progress
        // bytes transferred and total bytes etc
    }
);

Sending Data

Sending Bytes Payload

Nearby().sendBytesPayload(endpointId, bytes_array);

// payloads are recieved by callback given to acceptConnection method.

Sending File Payload

You need to send the File Payload and File Name seperately.

File is stored in DOWNLOAD_DIRECTORY/.nearby/ and given a generic name. You need to copy the file to another directory of your choice.

//creates file with generic name (without extension) in Downloads Directory
//its your responsibility to rename the file properly
Nearby().sendFilePayload(endpointId, filePath);

//Send filename as well so that receiver can move and rename the file
Nearby().sendBytesPayload(endpointId,fileNameEncodedWithPayloadId);
//e.g send a string like "payloadId:FileExtensionOrFullName" as bytes

//payloads are recieved by callback given to acceptConnection method.

Every payload has an ID which is same for sender and receiver.

You can get the uri of the file from Payload in onPayloadReceived function. We have a convenience method to copy the file to a location you want-

// Convenience method to copy file using it's `uri`.
final newPath = '${await getExternalStorageDirectory}/$fileName';
await Nearby().copyFileAndDeleteOriginal(uri, newPath);

Checkout the Example in Repository for more details.