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Nearby Service

Connecting phones in a P2P network

Xenikii Website LICENSE BSD Pub package Pub Likes

Nearby Service Flutter Plugin is used to create connections in a P2P network. The plugin supports sending text messages and files. With it, you can easily create any kind of information sharing application without Internet connection.

The package does not support communication between Android and IOS devices, the connection is available for Android-Android and IOS-IOS relations.

Your feedback and suggestions would be greatly appreciated! You can leave your opinion here

Table of Contents

About

A peer-to-peer (P2P) network is a decentralized network architecture in which each participant, called a peer, can act as both a client and a server. This means that peer-to-peer networks can exchange resources such as files, data or services directly with each other without needing a central authority or server.

About Android Plugin

For Android, Wi-fi Direct is used as a P2P network.

It is implemented through the android.net.wifi.p2p module. It requires permissions for ACCESS_FINE_LOCATION and NEARBY_WIFI_DEVICES (for Android 13+).

It is also important that you need Wi-fi enabled on your device to use it.

To check permissions and Wi-fi status, the nearby_service plugin includes a set of methods:

  • checkWifiService() (Android only): returns true if Wi-fi is enabled
  • requestPermissions() (Android only): requests permissions for location and nearby devices and returns true if granted
  • openServicesSettings(): opens Wi-fi settings for Android and general settings for iOS

Testing the plugin is not possible on Android emulators, as they usually do not contain the Wi-fi Direct function in general! Use physical devices for that.

About IOS Plugin

For IOS, the P2P connection is implemented through the Multipeer Connectivity framework.

This framework automatically selects the best network technology depending on the situation—using Wi-Fi if both devices are on the same network, or using peer-to-peer Wi-Fi or Bluetooth otherwise.

The module will work even with Wi-fi turned off (via Bluetooth), but you can still use openServicesSettings() from the nearby_service plugin to open the settings and prompt the user to turn Wi-fi on.

Features

  • Device Preparation

    • Requesting permissions to use Wi-Fi Direct (Android only)
    • Checking Wi-Fi status (Android only)
    • Opening settings to enable Wi-Fi (Android and iOS)
    • Role selection - Browser or Advertiser (IOS only)

  • Connecting to the Device from a P2P Network

    • Listening for discovered devices (peers)
    • Creating connections over the P2P network
    • Monitoring the status of the connected device

  • The Data Transmission Channel

    • Establishing the channel for data exchange
    • Monitoring the status of the channel

  • Typed Data Exchange

    • Transmitting text data over the P2P network
    • Receiving confirmation of successful text message delivery
    • Transmitting files over the P2P network
    • The option to confirm or deny receiving of files over the network

Setup

Android setup

All necessary Android permissions are already in the AndroidManifest.xml of the plugin, so you don't need to add anything to work with p2p network.

IOS setup

For IOS, you need to add the following values to Info.plist:

<key>NSBonjourServices</key>
  <array>
    <string>_mp-connection._tcp</string>
  </array>
<key>UIRequiresPersistentWiFi</key>
<true/>
<key>NSLocalNetworkUsageDescription</key>
<string>[Your description here]</string>

  • NSBonjourServices

    For the nearby_service plugin, you should add the value <string>_mp-connection._tcp</string>. This key is required for Multipeer Connectivity. It defines the Bonjour services that your application will look for. Bonjour is Apple's implementation of zero-configuration networking, which allows devices on a LAN to discover each other and establish connections without requiring manual configuration.

  • UIRequiresPersistentWiFi

    This key is not strictly required for Multipeer Connectivity to work. This key is used to indicate that your application requires a persistent Wi-Fi connection even when the screen is off. This can be useful for maintaining a network connection for continuous data transfer.

  • NSLocalNetworkUsageDescription

    This key is needed to inform users why your application will use the local network. You must provide a string value that explains why your application needs LAN access.

Note that if you want to use the plugin to send files, you also need to follow the instructions about permissions of the filesystem management package you are using.

Usage

The full example demonstrating the functionality can be viewed at the link.

Important note: for functionality that is only available for one of the platforms, you should use the corresponding API element from NearbyService.

For Android:

final _nearbyService = NearbyService.getInstance();
_nearbyService.android..

For IOS:

final _nearbyService = NearbyService.getInstance();
_nearbyService.ios..
  1. Import the package:
import 'package:nearby_service/nearby_service.dart';
  1. Create an instance of NearbyService:
// getInstance() returns an instance for the current platform.
final _nearbyService = NearbyService.getInstance();
  1. Initialize the plugin:
// You can change the device name on a P2P network only for iOS. 
// Optionally pass the [iosDeviceName].
await _nearbyService.initialize(
        data: NearbyInitializeData(iosDeviceName: iosDeviceName),
      );

Extra step for Android: ask for permissions and make sure Wi-fi is enabled:

final granted = await _nearbyService.android?.requestPermissions();
if (granted ?? false) {
  // go to the checking Wi-fi step
}

final isWifiEnabled = await _nearbyService.android?.checkWifiService();
if (isWifiEnabled ?? false) {
  // go to the starting discovery step
}

Extra step for IOS: ask the user to choose whether they are a Browser or Advertiser:

In IOS Multipeer Connectivity, there are 2 roles for the discovery process and connection between devices: browser and advertiser.

Browser: This component discovers nearby devices that report their availability. It is responsible for finding peers that advertise themselves and inviting them to join the shared session.

Advertiser: This component advertises the availability of the device to nearby peers. It is used to let know the browser that the device is available for inviting and connecting.

The code for selecting a role:

_nearbyService.ios?.setIsBrowser(value: isBrowser);
// go to the starting discovery step
  1. Start to discover the P2P network.
final result = await _nearbyService.discover();
if (result) {
   // go to the listening peers step
}
  1. Start listening to peers:
_nearbyService.getPeersStream().listen((event) => peers = event);
  1. Each of the peers is a NearbyDevice and you can connect to it:

Remember that when used on the Android platform, you can only pass NearbyAndroidDevice to the connect() method. Similarly for iOS, NearbyIOSDevice. Devices automatically come from the discovery state in the correct type, so you just need to use the received data.

final result = await _nearbyService.connect(device);
if (result) {
  // go the the listening the device step
}
  1. Once you are connected via P2P network, you can start listening to the connected device. If null comes from the stream, it means the devices lost connection.
_connectedDeviceSubscription = _nearbyService.getConnectedDeviceStream(device).listen(
  (event) async {
    final wasConnected = connectedDevice?.status.isConnected ?? false;
    final nowConnected = event?.status.isConnected ?? false;
    if (wasConnected && !nowConnected) {
      // return to the discovery state
    }
    connectedDevice = event;
  },
);
  1. Once you have connected over a P2P network, you still need to create a communication channel to transfer data. For Android, this is a socket embedded in NearbyService, for iOS it's a setup to listen to messages and resources from the desired device. There is a method startCommunicationChannel() for this purpose. You should pass to it listeners for messages and resources received from the connected device. There can only be one communication channel, if you create a new one, the previous one will be cancelled.
final messagesListener = NearbyServiceMessagesListener(
  onData: (message) {
    // handle the message from NearbyServiceMessagesListener
  },
);
final filesListener = NearbyServiceFilesListener(
  onData: (pack) async {
    // handle the files pack from NearbyServiceFilesListener
  }, 
);

await _nearbyService.startCommunicationChannel(
  NearbyCommunicationChannelData(
    connectedDevice.info.id,
    messagesListener: messagesListener,
    filesListener: filesListener,
  ),
);
  1. I think you've already guessed that since there are listeners of messages from another device, we can send them ourselves too :) There is a method send() for that:
_nearbyService.send(
  OutgoingNearbyMessage(
    content: NearbyMessageTextRequest.create(value: message),
    receiver: connectedDevice.info,
  ),
);

Data sharing

This is a very important topic for the nearby_service plugin because it provides unique functionality for sharing typed data.

First, it's essential to say that when you send a message, you are required to pass the OutgoingNearbyMessage model. This contains the receiver - the recipient to whom the message is addressed. The receiver is someone with whom you already have an established communication channel. Also OutgoingNearbyMessage contains a content field, it can be one of 4 types:

  • NearbyMessageTextRequest
  • NearbyMessageTextResponse
  • NearbyMessageFilesRequest
  • NearbyMessageFilesResponse

We will talk more about them later.

Second, there is another type of message, ReceivedNearbyMessage. This is what comes to you from the NearbyServiceMessagesListener. It contains a sender field so that you can identify who the message came from and use that information.

Text messages

Description of the operating logic:

  1. One of the devices sends a message using the send() method:
// DEVICE A
_nearbyService.send(
  OutgoingNearbyMessage(
    content: NearbyMessageTextRequest.create(value: message),
    receiver: connectedDevice.info,
  ),
);
  1. Another device receives the ReceivedNearbyMessage with content cast as NearbyMessageTextRequest from the NearbyServiceMessagesListener.
// DEVICE B
final messagesListener = NearbyServiceMessagesListener(
  onData: (message) {
    // message is ReceivedNearbyMessage with content cast as NearbyMessageTextRequest here
  },
);
  1. If you want the sender to make sure the message has been received, you can send them NearbyMessageTextResponse. You need to add the id from the received NearbyMessageTextRequest to it:
// DEVICE B
_nearbyService.send(
  OutgoingNearbyMessage(
    receiver: connectedDevice.info,
    content: NearbyMessageTextResponse(id: requestId),
  ),
);
  1. If everything is fine, the sender will receive your NearbyMessageTextResponse from their NearbyServiceMessagesListener:
// DEVICE A
final messagesListener = NearbyServiceMessagesListener(
  onData: (message) {
    // message is ReceivedNearbyMessage with content cast as NearbyMessageTextResponse here
  },
);

Throughout the process, you can use the ids of the messages to identify them.

Resource messages

Description of the operating logic:

  1. One of the devices sends a message with NearbyMessageFilesRequest using the send() method:
// DEVICE A
_nearbyService.send(
  OutgoingNearbyMessage(
    // files here is List<NearbyFileInfo>, it can be easily created from the file path: NearbyFileInfo(path: file.path)
    content: NearbyMessageFilesRequest.create(files: files),
    receiver: connectedDevice.info,
  ),
);
  1. Another device receives the ReceivedNearbyMessage with content cast as NearbyMessageFilesRequest from the NearbyServiceMessagesListener.

The file request comes from the NearbyServiceMessagesListener because it doesn't contain the transferred files, only the request to send them! For files, confirmation by the other party before starting the data transfer is required!

// DEVICE B
final messagesListener = NearbyServiceMessagesListener(
  onData: (message) {
    // message is ReceivedNearbyMessage with content cast as NearbyMessageFilesRequest here
  },
);
  1. In order to receive the files, the other party must confirm that it wants to do so and send a message with NearbyMessageFilesResponse content. The NearbyMessageFilesResponse contains the isAccepted field, which will determine whether the file sending will start or not.

If you don't want to use confirmation logic to send files, just send the automatic positive responses to NearbyMessageFilesRequest in NearbyServiceMessagesListener.

// DEVICE B
_nearbyService.send(
  OutgoingNearbyMessage(
    receiver: connectedDevice!.info,
    content: NearbyMessageFilesResponse(
      id: request.id,
      isAccepted: isAccepted,
    ),
  ),
);
  1. The sender will receive NearbyMessageFilesResponse in their NearbyServiceMessagesListener and can notify the user.
// DEVICE A
final messagesListener = NearbyServiceMessagesListener(
  onData: (message) {
    // message is ReceivedNearbyMessage with content cast as NearbyMessageFilesResponse here
  },
);

At this time under the hood, the sending of files will begin and the recipient will receive ReceivedNearbyFilesPack in the NearbyServiceFilesListener when sending is complete. ReceivedNearbyFilesPack holds the paths of the received files already stored on the device's temporary directory. You can overwrite them to the desired location, delete them, or do anything else you like.

// DEVICE B
final filesListener = NearbyServiceFilesListener(
  onData: (pack) async {
  // pack is ReceivedNearbyFilesPack here
  },
);

Exceptions

NearbyService includes custom errors that you can catch in your implementation.

Common exceptions See here:

  • NearbyServiceUnsupportedPlatformException: Usage of the plugin on an unsupported platform
  • NearbyServiceUnsupportedDecodingException: Error decoding messages from native platform to Dart (open an issue if this happens)
  • NearbyServiceInvalidMessageException: An attempt to send an invalid message on the sender's side. Add content validation to your messages

Exceptions that can be caught from the discover(), stopDiscovery(), connect(), and disconnect() methods for the Android platform See here:

  • NearbyServiceBusyException: The Wi-Fi P2P framework is currently busy. Usually this means that you have sent a request to some device and now one of the peers is CONNECTING
  • NearbyServiceP2PPUnsupportedException: Wi-Fi P2P is not supported on this device
  • NearbyServiceNoServiceRequestsException: No service discovery requests have been made. Ensure that you have initiated a service discovery request before attempting to connect
  • NearbyServiceGenericErrorException: A generic error occurred. This could be due to various reasons such as hardware issues, Wi-Fi being turned off, or temporary issues with the Wi-Fi P2P framework
  • NearbyServiceUnknownException: An unknown error occurred. Please check the device's Wi-Fi P2P settings and ensure the device supports Wi-Fi P2P

Additional options

  • Each NearbyDevice contains NearbyDeviceInfo that presents different meanings depending on the platform. For Android id is the MAC address of the device, and for iOS it is the unique identifier of its MCPeerID. In general, id identifies the device in its platform.

  • Use the getter communicationChannelState of NearbyService to know the state of the communication channel. It may be:

    enum CommunicationChannelState {
  notConnected,
  loading,
  connected;
  
  bool get isNotConnected => this == CommunicationChannelState.notConnected;
  
  bool get isLoading => this == CommunicationChannelState.loading;
  
  bool get isConnected => this == CommunicationChannelState.connected;
}

    The getter is ValueListenable so you can listen to its state.

  • There are methods getPlatformVersion() and getPlatformModel() of NearbyService to determine the version and model of the device respectively. You can use them to specify a name for the IOS.

  • Use getCurrentDeviceInfo() of NearbyService to get information about the current device on the P2P network. Note that the ID obtained from getCurrentDeviceInfo() for Android will always be 02:00:00:00:00:00 for privacy issues.

  • For Android, it is possible to listen to the current state of the connection using method getConnectionInfoStream of NearbyAndroidService.

  • When you are creating a service with getInstance(), you can define the logging level in the plugin using field logLevel. Possible logging levels:

    enum NearbyServiceLogLevel {
  debug,
  info,
  error,
  disabled,
}

Demo

Android

android_demo

IOS

IOS_demo

Libraries

nearby_service
nearby_service_method_channel
nearby_service_platform_interface