PeerFinder.ConnectAsync(PeerInformation) Method

Definition

Namespace:

Windows.Networking.Proximity

Connects to a peer discovered by a call to the FindAllPeersAsync method.

public:
 static IAsyncOperation<StreamSocket ^> ^ ConnectAsync(PeerInformation ^ peerInformation);

/// [Windows.Foundation.Metadata.RemoteAsync]
 static IAsyncOperation<StreamSocket> ConnectAsync(PeerInformation const& peerInformation);

[Windows.Foundation.Metadata.RemoteAsync]
public static IAsyncOperation<StreamSocket> ConnectAsync(PeerInformation peerInformation);

function connectAsync(peerInformation)

Public Shared Function ConnectAsync (peerInformation As PeerInformation) As IAsyncOperation(Of StreamSocket)

Parameters

peerInformation

PeerInformation

A peer information object representing the peer to connect to.

Returns

IAsyncOperation<StreamSocket>

An asynchronous operation for connecting to a remote peer using the supplied StreamSocket object.

Attributes

RemoteAsyncAttribute

Windows requirements

App capabilities

ID_CAP_NETWORKING [Windows Phone] ID_CAP_NETWORKING [Windows Phone] proximity ID_CAP_PROXIMITY [Windows Phone]

Examples

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

Remarks

You can obtain an instance of a PeerInformation object for a peer from a call to the FindAllPeersAsync method, or in a handler for the ConnectionRequested event.

If an app calls the ConnectAsync method to create a connection with a peer, the app will no longer advertise for a connection and will not be found by the FindAllPeersAsync method until the app calls the Close method to close the socket connection.

If you open a socket connection by calling the ConnectAsync method, only one socket connection can be open at a time for the computer. If your app, or another app calls the ConnectAsync method, then the existing socket connection will close.

An Access Denied exception will be thrown if you attempt to call ConnectAsync when your app is in the background.

Important

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

Windows Phone 8

Wi-Fi Direct is not supported on Windows Phone 8.

See also

• FindAllPeersAsync()
• PeerInformation
• ConnectionRequested
• Proximity and Tapping (C#/VB/C++)
• Proximity sample