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
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:name="android.permission.ACCESS_FINE_LOCATION" />

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

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

Note: Android 12+ has introduced some new bluetooh 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.

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.

Otherwise, as a convenience this library provides methods to check and request location and external read/write permissions

// returns true/false asynchronously.
bool a = await Nearby().checkLocationPermissions();
// asks for permission only if its not given
// returns true/false if the location permission is granted on/off resp.
bool b = await Nearby().askLocationPermission();

// OPTIONAL: if you need to transfer files and rename it on device
bool c = await  Nearby().checkExternalStoragePermission();
// asks for READ + WRTIE EXTERNAL STORAGE permission only if its not given
Nearby().askExternalStoragePermission();

Nearby().askLocationAndExternalStoragePermission(); // for all permissions in one go..

// For bluetooth permissions on Android 12+.
bool d = await Nearby().checkBluetoothPermission();
// asks for BLUETOOTH_ADVERTISE, BLUETOOTH_CONNECT, BLUETOOTH_SCAN permissions.
Nearby().askBluetoothPermission();

Work Flow

The work flow is similar to the Android Nearby Connections library

NOTE

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

For convenience this library provides methods to check and enable location

bool b = await Nearby().checkLocationEnabled();

// opens dialogue to enable location service
// returns true/false if the location service is turned on/off resp.
bool b = await Nearby().enableLocationServices();

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 convinience method to copy the file to a location you want-

// Convinience 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.

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mannprerak2 / nearby_connections

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