ProximityDevice.SubscribeForMessage(String, MessageReceivedHandler) ProximityDevice.SubscribeForMessage(String, MessageReceivedHandler) ProximityDevice.SubscribeForMessage(String, MessageReceivedHandler) ProximityDevice.SubscribeForMessage(String, MessageReceivedHandler) ProximityDevice.SubscribeForMessage(String, MessageReceivedHandler) Method

Definition

Creates a subscription for a specified message type.

public : long SubscribeForMessage(Platform::String messageType, MessageReceivedHandler messageReceivedHandler)
long SubscribeForMessage(winrt::hstring messageType, MessageReceivedHandler messageReceivedHandler) const;
public long SubscribeForMessage(String messageType, MessageReceivedHandler messageReceivedHandler)
Public Function SubscribeForMessage(messageType As String, messageReceivedHandler As MessageReceivedHandler) As long
var long = proximityDevice.subscribeForMessage(messageType, messageReceivedHandler);

Parameters

messageType
String String String

The type of message to deliver to this subscription.

messageReceivedHandler
MessageReceivedHandler MessageReceivedHandler MessageReceivedHandler

The handler that the proximity provider will call when it delivers a message.

Returns

long long long

A unique ID for the subscription.

Additional features and requirements

Capabilities
ID_CAP_PROXIMITY [Windows Phone] proximity ID_CAP_PROXIMITY [Windows Phone]

Examples

Windows.Networking.Proximity.ProximityDevice proximityDevice;
long publishedMessageId = -1;
long subscribedMessageId = -1;

private void initializeProximityDevice()
{
    proximityDevice = Windows.Networking.Proximity.ProximityDevice.GetDefault();

    if (proximityDevice != null)
    {
        PublishMessageButton.Click += PublishMessage;
        SubscribeForMessageButton.Click += SubscribeForMessage;
        StopSubscribingForMessageButton.Click += StopSubscribingForMessage;
        StopPublishingMessageButton.Click += StopPublishingMessage;
    }
    else
    {
        WriteMessageText("Failed to initialized proximity device.
"); } } private void PublishMessage(object sender, RoutedEventArgs e) { // Stop publishing the current message. if (publishedMessageId != -1) { proximityDevice.StopPublishingMessage(publishedMessageId); } publishedMessageId = proximityDevice.PublishMessage("Windows.SampleMessage", MessageTextBlock.Text); } private void SubscribeForMessage(object sender, RoutedEventArgs e) { // Only subscribe for the message one time. if (subscribedMessageId == -1) { subscribedMessageId = proximityDevice.SubscribeForMessage("Windows.SampleMessage", messageReceived); } } private void messageReceived( Windows.Networking.Proximity.ProximityDevice device, Windows.Networking.Proximity.ProximityMessage message) { MessageBlock.Text += "Message received: " + message.DataAsString + "
"; } private void StopSubscribingForMessage(object sender, RoutedEventArgs e) { proximityDevice.StopSubscribingForMessage(subscribedMessageId); subscribedMessageId = -1; } private void StopPublishingMessage(object sender, RoutedEventArgs e) { proximityDevice.StopPublishingMessage(publishedMessageId); publishedMessageId = -1; } // 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; }); }
    function id(elementId) {
        return document.getElementById(elementId);
    }

    var proximityDevice;
    var publishedMessageId = -1;
    var subscribedMessageId = -1;

    function initializeProximityDevice() {
        proximityDevice = Windows.Networking.Proximity.ProximityDevice.getDefault();

        if (proximityDevice) {
            id("publishMessageButton").addEventListener("click", publishMessage);
            id("subscribeForMessageButton").addEventListener("click", subscribeForMessage);
    id("stopSubscribingForMessageButton").addEventListener("click", 
        stopSubScribingForMessage);
    id("stopPublishingMessageButton").addEventListener("click", 
        stopPublishingMessage);
        }
        else {
            id("messageDiv").innerHTML += "Failed to initialized proximity device.<br />";
        }
    }

    function publishMessage() {
        // Stop publishing the current message.
        if (publishedMessageId != -1) {
            proximityDevice.stopPublishingMessage(publishedMessageId);
        }

        publishedMessageId = 
    proximityDevice.publishMessage("Windows.SampleMessage", id("messageText").value);
    }

    function subscribeForMessage() {
        // Only subscribe for the message one time.
        if (subscribedMessageId === -1) {
            subscribedMessageId = 
        proximityDevice.subscribeForMessage("Windows.SampleMessage", messageReceived);
        }
    }

    function messageReceived(device, message) {
        id("messageDiv").innerHTML += "Message received: " + message.dataAsString + "<br />";
    }

function stopSubscribingForMessage() {
    proximityDevice.stopSubscribingForMessage(subscribedMessageId);
        subscribedMessageId = -1;
}

function stopPublishingMessage() {
    proximityDevice.stopPublishingMessage(publishedMessageId);
        publishedMessageId = -1;
}
Private proximityDevice As Windows.Networking.Proximity.ProximityDevice
Private publishedMessageId As Long = -1
Private subscribedMessageId As Long = -1

Private Sub initializeProximityDevice()
    proximityDevice = Windows.Networking.Proximity.ProximityDevice.GetDefault()

    If proximityDevice IsNot Nothing Then
        AddHandler PublishMessageButton.Click, AddressOf PublishMessage
        AddHandler SubscribeForMessageButton.Click, AddressOf SubscribeForMessage
        AddHandler StopSubscribingForMessageButton.Click, AddressOf StopSubscribingForMessage
        AddHandler StopPublishingMessageButton.Click, AddressOf StopPublishingMessage
    Else
        WriteMessageText("Failed to initialized proximity device." & vbTab)
    End If
End Sub

Private Sub PublishMessage(sender As Object, e As RoutedEventArgs)
    ' Stop publishing the current message.
    If publishedMessageId <> -1 Then
        proximityDevice.StopPublishingMessage(publishedMessageId)
    End If

    publishedMessageId =
        proximityDevice.PublishMessage("Windows.SampleMessage", MessageTextBlock.Text)
End Sub

Private Sub SubscribeForMessage(sender As Object, e As RoutedEventArgs)
    ' Only subscribe for the message one time.
    If subscribedMessageId = -1 Then
        subscribedMessageId =
        proximityDevice.SubscribeForMessage("Windows.SampleMessage", AddressOf messageReceived)
    End If
End Sub

Private Sub messageReceived(
    device As Windows.Networking.Proximity.ProximityDevice,
    message As Windows.Networking.Proximity.ProximityMessage)

    MessageBlock.Text &= "Message received: " & message.DataAsString & vbTab
End Sub

Private Sub StopSubscribingForMessage(sender As Object, e As RoutedEventArgs)
    proximityDevice.StopSubscribingForMessage(subscribedMessageId)
    subscribedMessageId = -1
End Sub

Private Sub StopPublishingMessage(sender As Object, e As RoutedEventArgs)
    proximityDevice.StopPublishingMessage(publishedMessageId)
    publishedMessageId = -1
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

Remarks

After your app calls the SubscribeForMessage method, it will receive messages that are published with the same message type (as indicated by the messageType parameter) from any proximate devices. For details on the different message types, see the remarks in the PublishBinaryMessage(String, IBuffer) reference topic.

You can cancel a subscription by passing the subscription ID that's returned by the SubscribeForMessage method to the StopSubscribingForMessage method.

You can publish a message to a subscriber by using the PublishMessage, PublishBinaryMessage, or PublishUriMessage method.

Important

The proximity APIs do not provide authentication, encryption, or message integrity. Do not use proximity to exchange user sensitive information such as passwords, financial data, text messages, email, photographs, or government id numbers.

See also