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ProximityDevice.PublishMessage(String, String) | publishMessage(String, String) method

Applies to Windows and Windows Phone

Publishes a message to subscribers of the specified message type.

Syntax


var number = proximityDevice.publishMessage(messageType, message);

public long PublishMessage(
  string messageType, 
  string message
)

Public Function PublishMessage(
  messageType As String,  
  message As String 
) As Long

public:
long long PublishMessage(
  String^ messageType, 
  String^ message
)

Parameters

messageType

Type: String [JavaScript] | System.String [.NET] | Platform::String [C++]

The type of message to deliver to subscribers.

message

Type: String [JavaScript] | System.String [.NET] | Platform::String [C++]

The message to deliver to subscribers.

Return value

Type: Number [JavaScript] | System.Int64 [.NET] | int64 [C++]

A unique publication ID for the published message. Pass this value to the StopPublishingMessage method to stop publishing the message.

Remarks

You can subscribe to published messages by using the SubscribeForMessage method.

Messages continue to be published until the StopPublishingMessage method is called or the ProximityDevice object is released.

Messages are delivered to all applications that have subscribed to the message type (as indicated by the messageType parameter). Message type values are case-sensitive strings that consist of two parts: the protocol and the subtype. The protocol is first, followed by a dot (.) and then the subtype. For the PublishMessage method, the protocol must always be "Windows.". The subtype is a string of alphanumeric characters and the following additional characters: . ( ) + , - : = @ ; $ _ ! * ’. The subtype cannot exceed a length of 250 characters.

To publish messages by using another message type, like “WindowsMime.” or “NDEF:WriteTag”, you must use the PublishBinaryMessage method.

You can use the PublishUriMessage method to publish a Uniform Resource Identifier (URI) to a proximate computer.

Messages are converted to UTF-8 characters before they're transmitted.

For Windows Store apps, publications and subscriptions are active only if the calling app is in the foreground.

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.

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.\n");
    }
}

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 + "\n";
}

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

Requirements

Minimum supported client

Windows 8

Minimum supported server

Windows Server 2012

Minimum supported phone

Windows Phone 8

Namespace

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

Metadata

Windows.winmd

Capabilities

proximity
ID_CAP_PROXIMITY [Windows Phone]

See also

ProximityDevice
PublishMessage(String, String, MessageTransmittedHandler)
PublishBinaryMessage
PublishUriMessage
StopPublishingMessage
Proximity and Tapping (JavaScript)
Proximity and Tapping (C#/VB/C++)
Samples
Proximity sample