Connection Lifecycle

Once the connection to the broker has been established, the IConnection interface can notify you about several important events that may occur throughout the connection lifecycle.

Connection Closed

IConnection.ConnectionClosed will be raised when the connection to the broker has been lost.

var connectionFactory = new ConnectionFactory();
var connection = await connectionFactory.CreateAsync(endpoint);
connection.ConnectionClosed += (sender, eventArgs) =>
{
    // react accordingly
};

When the connection was created with enabled automatic recovery, this event may be raised multiple times. Without automatic recovery this notification signifies that you won't be able to use this connection anymore.

ConnectionClosed event is raised with ConnectionClosedEventArgs parameter. You can inspect it to check the error that caused the connection to be terminated:

connection.ConnectionClosed += (sender, eventArgs) =>
{
    // reason the connection was closed  
    string reason = eventArgs.Error;
    _logger.LogWarning(reason);
};

Or you can verify whether the connection was closed by the remote peer (broker) or not:

connection.ConnectionClosed += (sender, eventArgs) =>
{
    bool closedByPeer = eventArgs.ClosedByPeer;
    if (closedByPeer) 
    {
        _logger.LogWarning("connection was closed by the broker");
    }
    else
    {
        _logger.LogWarning("connection was closed by the client");
    }
};

You can also check if the connection is open by inspecting IsOpened property:

var connectionFactory = new ConnectionFactory();
var connection = await connectionFactory.CreateAsync(endpoint);
if (connection.IsOpened)
{
    // connection is still opened
}
else
{
    // connection to the broker has been lost
}

## Maintaining Connection Stability with TCP Keep-Alive

To enhance connection stability and prevent unexpected disconnections, consider configuring TCP Keep-Alive settings. This feature sends periodic signals to ensure the connection remains active, especially useful in unstable network environments.

```csharp
var factory = new ConnectionFactory();
// Configure TCP Keep-Alive settings
factory.TCP.KeepAliveTime = 30_000; // 30 seconds
factory.TCP.KeepAliveInterval = 1000; // 1 second

By setting KeepAliveTime and KeepAliveInterval, you can help ensure that your application maintains a reliable connection to the broker, complementing the event-driven connection management strategies outlined above.