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PeerFinder class

Enables you to discover other instances of your app on nearby devices and create a socket connection between the peer apps by using a tap gesture or by browsing. For creating Bluetooth socket connections on Windows 8.1 and later, use Windows.Devices.Bluetooth.Rfcomm instead.

Syntax


var peerFinder = Windows.Networking.Proximity.PeerFinder;

public static class PeerFinder

Public NotInheritable Class PeerFinder

public ref class PeerFinder abstract sealed 

Members

The PeerFinder class has these types of members:

Events

The PeerFinder class has these events.

EventDescription
ConnectionRequested Occurs when a remote peer requests a connection using the ConnectAsync method.
TriggeredConnectionStateChanged Occurs during a tap gesture from a remote peer.

 

Methods

The PeerFinder class has these methods. With C#, Visual Basic, and C++, it also inherits methods from the Object class.

MethodDescription
ConnectAsync Connects to a peer discovered by a call to the FindAllPeersAsync method.
CreateWatcher Creates a new instance of a PeerWatcher object for dynamic discovery of peer apps.
FindAllPeersAsync Asynchronously browses for peer devices that are running the same app within wireless range.
Start() Makes an app discoverable to remote peers.
Start(String) Makes an app discoverable to remote peers.
Stop Stops advertising for a peer connection.

 

Properties

The PeerFinder class has these properties.

PropertyAccess typeDescription

AllowBluetooth

Read/write

Specifies whether the PeerFinder class may connect a StreamSocket object by using Bluetooth.

AllowInfrastructure

Read/write

Specifies whether the PeerFinder class may connect to a StreamSocket object using TCP/IP.

AllowWiFiDirect

Read/write

Specifies whether the PeerFinder class may connect a StreamSocket object by using Wi-Fi Direct.

AlternateIdentities

Read-only

Gets a list of alternate appId values to match with peer applications on other platforms.

DiscoveryData

Read/write

Gets or sets user or device data to include during device discovery.

DisplayName

Read/write

Gets or sets the name that identifies your computer to remote peers.

Role

Read/write

Gets or sets the role of the app in peer-to-peer connections.

SupportedDiscoveryTypes

Read-only

Gets a value that indicates which discovery options are available to use with the PeerFinder class.

 

Remarks

Important  

The Proximity APIs do not provide authentication. You should avoid exchanging sensitive data with these APIs.

 

Examples


var started = false;

// Click event for "Advertise" button.
function advertiseForPeers(launchedFromTap) {
    Windows.Networking.Proximity.PeerFinder.displayName = displayNameTextBox.Text;

    if (Windows.Networking.Proximity.PeerFinder.supportedDiscoveryTypes &
        Windows.Networking.Proximity.PeerDiscoveryTypes.triggered) {

        Windows.Networking.Proximity.PeerFinder.addEventListener(
            "triggeredconnectionstatechanged", triggeredConnectionStateChanged);

        id("messageDiv").innerHTML +=
            "You can tap to connect a peer device that is " +
            "also advertising for a connection.<br />";
    } else {
        id("messageDiv").innerHTML +=
            "Tap to connect is not supported.<br />";
    }

    if (!launchedFromTap) {
        if (!(Windows.Networking.Proximity.PeerFinder.SupportedDiscoveryTypes &
              Windows.Networking.Proximity.PeerDiscoveryTypes.Browse)) {
            id("messageDiv").innerHTML +=
                "Peer discovery using Wi-Fi Direct is not supported.<br />";
        }
    }

    if (!started) {
        Windows.Networking.Proximity.PeerFinder.start();
        started = true;
    }
}

function triggeredConnectionStateChanged(e) {
    if (e.state === Windows.Networking.Proximity.TriggeredConnectState.peerFound) {
        id("messageDiv").innerHTML +=
            "Peer found. You may now pull your devices out of proximity.<br />";
    }
    if (e.state === Windows.Networking.Proximity.TriggeredConnectState.completed) {
        id("messageDiv").innerHTML += "Connected. You may now send a message.<br />";
        sendMessage(e.socket);
    }
}


// Click event for "Browse" button.
function findPeers() {
    if (Windows.Networking.Proximity.PeerFinder.supportedDiscoveryTypes &
        Windows.Networking.Proximity.PeerDiscoveryTypes.browse) {

        Windows.Networking.Proximity.PeerFinder.findAllPeersAsync().done(
    function (peerInfoCollection) {
        if (peerInfoCollection.length > 0) {
            // Connect to first peer found - example only.
            // In your app, provide the user with a list of available peers.
            connectToPeer(peerInfoCollection[0]);
        }
    },
    function (err) {
        id("messageDiv").innerHTML += "Error finding peers: " + err + "<br />";
    });
    } else {
        id("messageDiv").innerHTML +=
        "Peer discovery using Wi-Fi Direct is not supported.<br />";
    }
}

function connectToPeer(peerInfo) {
    id("messageDiv").innerHTML += ("Peer found. Connecting to " + peerInfo.displayName + "<br />");
    Windows.Networking.Proximity.PeerFinder.connectAsync(peerInfo).done(
        function (socket) {
            id("messageDiv").innerHTML += "Connection successful. You may now send messages.<br />";
            sendMessage(socket);
        },
        function (err) {
            id("messageDiv").innerHTML += "Connection failed: " + err + "<br />";
        });

    requestingPeer = null;
}

function stopFindingPeers() {
    Windows.Networking.Proximity.PeerFinder.stop();
    started = false;
    if (proximitySocket != null) { closeSocket(); }
}

// Handle external connection requests.
var requestingPeer;

function connectionRequested(e) {
    id("messageDiv").innerHTML +=
        "Connection requested by " + e.peerInformation.DisplayName + ". " +
        "Click 'Accept Connection' to connect.";
    requestingPeer = e.PeerInformation;
}

function acceptConnection() {
    if (requestingPeer == null) {
        id("messageDiv").innerHTML += "No peer connection has been requested.";
        return;
    }

    connectToPeer(requestingPeer);
}

protected override void OnNavigatedTo(NavigationEventArgs e)
{
    DisplayNameTextBox.Text = Windows.Networking.Proximity.PeerFinder.DisplayName;
    Windows.Networking.Proximity.PeerFinder.ConnectionRequested += ConnectionRequested;

    // If activated from launch or from the background, create a peer connection.
    var args = e.Parameter as Windows.ApplicationModel.Activation.LaunchActivatedEventArgs;
    if (args != null && args.Kind == Windows.ApplicationModel.Activation.ActivationKind.Launch)
    {
        if (args.Arguments == "Windows.Networking.Proximity.PeerFinder:StreamSocket")
        {
            AdvertiseForPeersButton_Click(null, null);
        }
    }
}

protected override void OnNavigatingFrom(NavigatingCancelEventArgs e)
{
    if (_started)
    {
        // Detach the callback handler (there can only be one PeerConnectProgress handler).
        Windows.Networking.Proximity.PeerFinder.TriggeredConnectionStateChanged -= TriggeredConnectionStateChanged;
        // Detach the incoming connection request event handler.
        Windows.Networking.Proximity.PeerFinder.ConnectionRequested -= ConnectionRequested;
        Windows.Networking.Proximity.PeerFinder.Stop();
        CloseSocket();
        _started = false;
    }
}

// Write a message to MessageBlock on the UI thread.
private Windows.UI.Core.CoreDispatcher messageDispatcher = Window.Current.CoreWindow.Dispatcher;

async private void WriteMessageText(string message, bool overwrite = false)
{
    await messageDispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
        () =>
        {
            if (overwrite)
                MessageBlock.Text = message;
            else
                MessageBlock.Text += message;
        });
}

bool _started = false;

// Click event handler for "Advertise" button.
private void AdvertiseForPeersButton_Click(object sender, RoutedEventArgs e)
{
    if (_started) 
    {
        WriteMessageText("You are already advertising for a connection.\n");
        return; 
    }

    Windows.Networking.Proximity.PeerFinder.DisplayName = DisplayNameTextBox.Text;

    if ((Windows.Networking.Proximity.PeerFinder.SupportedDiscoveryTypes &
         Windows.Networking.Proximity.PeerDiscoveryTypes.Triggered) ==
         Windows.Networking.Proximity.PeerDiscoveryTypes.Triggered)
    {
        Windows.Networking.Proximity.PeerFinder.TriggeredConnectionStateChanged +=
            TriggeredConnectionStateChanged;

        WriteMessageText("You can tap to connect a peer device that is " +
                         "also advertising for a connection.\n");
    }
    else
    {
        WriteMessageText("Tap to connect is not supported.\n");
    }

    if ((Windows.Networking.Proximity.PeerFinder.SupportedDiscoveryTypes &
         Windows.Networking.Proximity.PeerDiscoveryTypes.Browse) !=
         Windows.Networking.Proximity.PeerDiscoveryTypes.Browse)
    {
        WriteMessageText("Peer discovery using Wi-Fi Direct is not supported.\n");
    }

   Windows.Networking.Proximity.PeerFinder.Start();
   _started = true;
}

private void TriggeredConnectionStateChanged(
    object sender,
    Windows.Networking.Proximity.TriggeredConnectionStateChangedEventArgs e)
{
    if (e.State == Windows.Networking.Proximity.TriggeredConnectState.PeerFound)
    {
        WriteMessageText("Peer found. You may now pull your devices out of proximity.\n");
    }
    if (e.State == Windows.Networking.Proximity.TriggeredConnectState.Completed)
    {
        WriteMessageText("Connected. You may now send a message.\n");
        SendMessage(e.Socket);
    }
}

// Click event handler for "Browse" button.
async private void FindPeersButton_Click(object sender, RoutedEventArgs e)
{
    if ((Windows.Networking.Proximity.PeerFinder.SupportedDiscoveryTypes &
         Windows.Networking.Proximity.PeerDiscoveryTypes.Browse) !=
         Windows.Networking.Proximity.PeerDiscoveryTypes.Browse)
    {
        WriteMessageText("Peer discovery using Wi-Fi Direct is not supported.\n");
        return;
    }

    try
    {
        var peerInfoCollection = await Windows.Networking.Proximity.PeerFinder.FindAllPeersAsync();
        if (peerInfoCollection.Count > 0)
        {
            // Connect to first peer found - example only.
            // In your app, provide the user with a list of available peers.
            ConnectToPeer(peerInfoCollection[0]);
        }
    }
    catch (Exception err)
    {
        WriteMessageText("Error finding peers: " + err.Message + "\n");
    }
}

async private void ConnectToPeer(Windows.Networking.Proximity.PeerInformation peerInfo)
{
    WriteMessageText("Peer found. Connecting to " + peerInfo.DisplayName + "\n");
    try
    {
        Windows.Networking.Sockets.StreamSocket socket =
            await Windows.Networking.Proximity.PeerFinder.ConnectAsync(peerInfo);

        WriteMessageText("Connection successful. You may now send messages.\n");
        SendMessage(socket);
    }
    catch (Exception err)
    {
        WriteMessageText("Connection failed: " + err.Message + "\n");
    }

    requestingPeer = null;
}

// Click event handler for "Stop" button.
private void StopFindingPeersButton_Click(object sender, RoutedEventArgs e)
{
    _started = false;
    Windows.Networking.Proximity.PeerFinder.Stop();
    if (proximitySocket != null) { CloseSocket(); }
}

// Handle external connection requests.
Windows.Networking.Proximity.PeerInformation requestingPeer;

private void ConnectionRequested(object sender,
    Windows.Networking.Proximity.ConnectionRequestedEventArgs e)
{
    requestingPeer = e.PeerInformation;
    WriteMessageText("Connection requested by " + requestingPeer.DisplayName + ". " +
        "Click 'Accept Connection' to connect.");
}

private void AcceptConnectionButton_Click(object sender, RoutedEventArgs e)
{
    if (requestingPeer == null)
    {
        WriteMessageText("No peer connection has been requested.");
        return;
    }

    ConnectToPeer(requestingPeer);
}

Protected Overrides Sub OnNavigatedTo(e As Navigation.NavigationEventArgs)
    DisplayNameTextBox.Text = Windows.Networking.Proximity.PeerFinder.DisplayName
    AddHandler Windows.Networking.Proximity.PeerFinder.ConnectionRequested, AddressOf ConnectionRequested

    ' If activated from launch or from the background, create a peer connection.
    Dim args = TryCast(e.Parameter, Windows.ApplicationModel.Activation.LaunchActivatedEventArgs)
    If args IsNot Nothing AndAlso args.Kind = Windows.ApplicationModel.Activation.ActivationKind.Launch Then

        If args.Arguments = "Windows.Networking.Proximity.PeerFinder:StreamSocket" Then
            AdvertiseForPeersButton_Click()
        End If
    End If
End Sub

Protected Overrides Sub OnNavigatingFrom(e As Navigation.NavigatingCancelEventArgs)
    If _started Then
        ' Detach the callback handler (there can only be one PeerConnectProgress handler).
        RemoveHandler Windows.Networking.Proximity.PeerFinder.TriggeredConnectionStateChanged, AddressOf TriggeredConnectionStateChanged
        ' Detach the incoming connection request event handler.
        RemoveHandler Windows.Networking.Proximity.PeerFinder.ConnectionRequested, AddressOf ConnectionRequested
        Windows.Networking.Proximity.PeerFinder.Stop()
        CloseSocket()
        _started = False
    End If
End Sub

' Write a message to MessageBlock on the UI thread.
Private Async Sub WriteMessageText(message As String, Optional overwrite As Boolean = False)
    Await Dispatcher.RunAsync(Windows.UI.Core.CoreDispatcherPriority.Normal,
        Sub()
            If overwrite Then
                MessageBlock.Text = message
            Else
                MessageBlock.Text &= message
            End If
        End Sub)
End Sub

Private _started As Boolean = False

' Click event handler for "Advertise" button.
Private Sub AdvertiseForPeersButton_Click()

    If _started Then
        WriteMessageText("You are already advertising for a connection." & vbCrLf)
        Return
    End If

    Windows.Networking.Proximity.PeerFinder.DisplayName = DisplayNameTextBox.Text

    If ((Windows.Networking.Proximity.PeerFinder.SupportedDiscoveryTypes And
         Windows.Networking.Proximity.PeerDiscoveryTypes.Triggered) =
         Windows.Networking.Proximity.PeerDiscoveryTypes.Triggered) Then

        AddHandler Windows.Networking.Proximity.PeerFinder.TriggeredConnectionStateChanged,
            AddressOf TriggeredConnectionStateChanged

        WriteMessageText("You can tap to connect a peer device that is " &
                         "also advertising for a connection." & vbCrLf)
    Else
        WriteMessageText("Tap to connect is not supported." & vbCrLf)
    End If

    If (Windows.Networking.Proximity.PeerFinder.SupportedDiscoveryTypes And
        Windows.Networking.Proximity.PeerDiscoveryTypes.Browse) <>
        Windows.Networking.Proximity.PeerDiscoveryTypes.Browse Then

        WriteMessageText("Peer discovery using Wifi-Direct is not supported." & vbCrLf)
    End If

    Windows.Networking.Proximity.PeerFinder.Start()
    _started = True
End Sub

Private Sub TriggeredConnectionStateChanged(
    sender As Object,
    e As Windows.Networking.Proximity.TriggeredConnectionStateChangedEventArgs)

    If e.State = Windows.Networking.Proximity.TriggeredConnectState.PeerFound Then

        WriteMessageText("Peer found. You may now pull your devices out of proximity." & vbCrLf)
    End If

    If e.State = Windows.Networking.Proximity.TriggeredConnectState.Completed Then
        WriteMessageText("Connected. You may now send a message." & vbCrLf)
        SendMessage(e.Socket)
    End If
End Sub

' Click event handler for "Browse" button.
Private Async Sub FindPeersButton_Click()
    If (Windows.Networking.Proximity.PeerFinder.SupportedDiscoveryTypes And
        Windows.Networking.Proximity.PeerDiscoveryTypes.Browse) <>
        Windows.Networking.Proximity.PeerDiscoveryTypes.Browse Then

        WriteMessageText("Peer discovery using Wifi-Direct is not supported." & vbCrLf)
        Return
    End If

    Try
        Dim peerInfoCollection = Await Windows.Networking.Proximity.PeerFinder.FindAllPeersAsync()
        If peerInfoCollection.Count > 0 Then
            ' Connect to first peer found - example only.
            ' In your app, provide the user with a list of available peers.
            ConnectToPeer(peerInfoCollection(0))
        End If
    Catch err As Exception
        WriteMessageText("Error finding peers: " & err.Message & vbCrLf)
    End Try
End Sub

Private Async Sub ConnectToPeer(peerInfo As Windows.Networking.Proximity.PeerInformation)

    WriteMessageText("Peer found. Connecting to " & peerInfo.DisplayName & vbCrLf)
    Try
        Dim socket = Await Windows.Networking.Proximity.PeerFinder.ConnectAsync(peerInfo)

        WriteMessageText("Connection successful. You may now send messages." & vbCrLf)
        SendMessage(socket)
    Catch err As Exception
        WriteMessageText("Connection failed: " & err.Message & vbCrLf)
    End Try

    requestingPeer = Nothing
End Sub

' Click event handler for "Stop" button.
Private Sub StopFindingPeersButton_Click()

    _started = False
    Windows.Networking.Proximity.PeerFinder.Stop()
    If proximitySocket IsNot Nothing Then CloseSocket()
End Sub

' Handle external connection requests.
Private requestingPeer As Windows.Networking.Proximity.PeerInformation

Private Sub ConnectionRequested(sender As Object,
    e As Windows.Networking.Proximity.ConnectionRequestedEventArgs)

    requestingPeer = e.PeerInformation

    WriteMessageText("Connection requested by " & requestingPeer.DisplayName & ". " &
        "Click 'Accept Connection' to connect.")
End Sub

Private Sub AcceptConnectionButton_Click()
    If requestingPeer Is Nothing Then
        WriteMessageText("No peer connection has been requested.")
        Return
    End If

    ConnectToPeer(requestingPeer)
End Sub

Requirements (Windows 10 device family)

Device family

Universal, introduced version 10.0.10240.0 [for Xbox, see UWP features that aren't yet supported on Xbox]

API contract

Windows.Foundation.UniversalApiContract, introduced version 1.0

Namespace

Windows.Networking.Proximity
Windows::Networking::Proximity [C++]

Metadata

Windows.Foundation.UniversalApiContract.winmd

Capabilities

proximity

Requirements (Windows 8.x and Windows Phone 8.x)

Minimum supported client

Windows 8 [Windows Store apps only]

Minimum supported server

Windows Server 2012 [Windows Store apps only]

Minimum supported phone

Windows Phone 8

Namespace

Windows.Networking.Proximity
Windows::Networking::Proximity [C++]

Metadata

Windows.winmd

Capabilities

proximity
ID_CAP_PROXIMITY [Windows Phone]
ID_CAP_NETWORKING [Windows Phone]

Attributes

[ MarshalingBehavior(Agile)]
[ Threading(Both)]
[ Version(0x06020000)]

See also

Object
Proximity and Tapping (JavaScript)
Proximity and Tapping (C#/VB/C++)
Samples
Proximity sample