This topic has not yet been rated - Rate this topic

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

Publishes a message to subscribers of the specified message type. The specified handler is called when the message has been transmitted.

Syntax

C++


public long PublishMessage(
  string messageType, 
  string message, 
  MessageTransmittedHandler messageTransmittedHandler
)

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.

messageTransmittedHandler

Type: MessageTransmittedHandler

The handler to call when the message has been transmitted.

Return value

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

A unique publication ID for the published 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.

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,
                                               MessagePublished);
}

    private void MessagePublished(
Windows.Networking.Proximity.ProximityDevice sender,
    long messageId)
{
// The message has been successfully published.
}

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;
        });
}

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]