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Signaling — Windows

Use the OpenTok signaling API to send text and data between clients connected to an OpenTok session.

For conceptual information on the OpenTok signaling API, see the Signaling overview developer guide.

This topic includes the following sections:

Sending a signal to a specific client in a session

To send a signal to a specific client in a session, call the Session.SendSignal(type, data, connection, retryAfterReconnect) method of the Session object:

Session.SendSignal("chat", "Hello", connection1);

The type parameter is a string value that clients can filter on when listening for signals. Set this to an empty string if you do not need to set a type.

The data parameter is the data payload (a string) you send with the message. The limit to the size of data is 8KB.

The connection parameter is a Connection object corresponding to a client connected to the session that you want to signal. You obtain references to Connection objects in the Connection property of the ConnectionEventArgs object used by the ConnectionCreated event sent by the Session object.

The retryAfterReconnect parameter is an optional parameter that determines whether the signal will be sent after an automatic reconnection. See Preventing signals from being sent during automatic reconnection.

Sending a signal to all clients in a session

To send a signal to all clients in a session, call the Session.SendSignal() method and leave the connection parameter unset (the default value is null):

session.SendSignal("chat", "Hello");

The first parameter, type, is a string value that clients can filter on when listening for signals. Set this to an empty string if you do not need to set a type.

The second parameter, signal, is the data payload (a string) you send with the message. The limit to the size of data is 8KB.

Receiving signals in a session

To start receive signals, add a delegate for the Signal method of the Session object:

session.Signal += Session_Signal;

private void Session_Signal(object sender, SignalEventArgs e)
{
    Console.WriteLine("Session received signal. ");
    Console.WriteLine("Data:" + e.Data);
    Console.WriteLine("Type:" + e.Type);
    Console.WriteLine("From connection with ID:" + e.Connection.Id);
}

The delegate method is called when a signal is received in the session.

You can check to see if the signal was received from your client by comparing the .

@Override
  private void Session_Signal(object sender, SignalEventArgs e)
  {
    String myConnectionId = session.Connection.ID;
    if (e.Connection != null && e.Connection.ID != myConnectionId) {
        // Signal received from another client
    }
}

Note that you can use a REST API call to send a signal from your server, instead of from a client connected to the session. In this case, the Connection property of the SignalEventArgs object is set to null.

Preventing signals from being sent during automatic reconnection

Clients will attempt to automatically reconnect to a session they disconnect unexpectedly (for example, due to a drop in network connectivity). By default, any signals you send while the client is temporarily disconnected from a session are queued and sent when (and if) it successfully reconnects. You can set the retryAfterReconnect) parameter of the Session.SendSignal() method to false to prevent signals from being queued while the client is disconnected. For more information, see Automatic reconnection.