FAQ

Table Of Contents

Logging

"Access to the path is denied" error

Detecting Connected and Disconnected events

ConnectToServer vs TryConnectToServer and SubscribeOnServer vs TrySubscribeOnServer

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Logging

Meta.Lib uses ILogger interface from Microsoft.Extensions.Logging namespace to log its internal events and errors. The TestServer demo application contains an example of how to create an ILogger implementation for the console application.

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"Access to the path is denied" error

You may receive this message if the server-side MetaPubSub runs in a Windows process with elevated permissions but the client process is not. In this case, you need to define your own delegate method to create NamedPipeServerStream.

Note: your server project must be created for .Net Framework, not .Net Core. See TestServer example application for complete source codes.

hub.StartServer("Meta", () =>
{
    var pipeSecurity = new PipeSecurity();
    pipeSecurity.AddAccessRule(new PipeAccessRule(
        new SecurityIdentifier(WellKnownSidType.BuiltinUsersSid, null),
        PipeAccessRights.FullControl,
        AccessControlType.Allow));

    var pipe = new NamedPipeServerStream("Meta", PipeDirection.InOut, 32,
        PipeTransmissionMode.Message, PipeOptions.Asynchronous, 4096, 4096, pipeSecurity);

    return pipe;
});

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Detecting Connected and Disconnected events

There are four built-in message you can subscribe for:

• RemoteClientConnectedEvent - publishes on the server hub when a client connects
• RemoteClientDisconnectedEvent - publishes on the server hub when a client disconnects
• ConnectedToServerEvent - publishes on the client hub when it connects to the server
• DisconnectedFromServerEvent - publishes on the client hub when it disconnects from the server

You can subscribe RemoteClientConnectedEvent and RemoteClientDisconnectedEvent on the server hub. These events have following properties:

• DateTime Timestamp - date and time when connection/disconnection event has happened (local server time)
• int TotalClientsCount - total count of the clients after the event

You can subscribe ConnectedToServerEvent on the client hub. It has the following properties:

• DateTime Timestamp - date and time when connection/disconnection event has happened (local client time)

You can subscribe DisconnectedFromServerEvent on the client hub. It has the following properties:

• DateTime Timestamp - date and time when connection/disconnection event has happened (local client time)
• bool LostConnection - if true than connection was lost for some reason, otherwise it has been closed using DisconnectFromServer method

Example:

// server hub
var serverHub = new MetaPubSub();
serverHub.StartServer("Meta");

serverHub.Subscribe<RemoteClientConnectedEvent>(ConnectedHandler);
serverHub.Subscribe<RemoteClientDisconnectedEvent>(DisconnectedHandler);

// client hub
var hub = new MetaPubSub();

hub.Subscribe<ConnectedToServerEvent>(ConnectedToServerHandler);
hub.Subscribe<DisconnectedFromServerEvent>(DisconnectedFromServerHandler);

await hub.ConnectToServer("Meta");
await hub.DisconnectFromServer();

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ConnectToServer vs TryConnectToServer and SubscribeOnServer vs TrySubscribeOnServer

When a client loses its connection to the server, it can automatically re-establish the connection. So you don't need the logic for listening for Disconnected/Connected events and resubscribing all required messages. However, if the Server is not yet started calling the SubscribeOnServer method will result in an exception. To address this, we could implement logic to wait for a connection and subscribe to the necessary events. However, this would require duplicating the code for each class that subscribes to server events, leading to code bloat.

To simplify this process, we can use the TryConnect and TrySubscribeOnServer methods.

• TryConnect establishes a connection to the server as soon as it's available, returning true if the connection is established during the call, and false otherwise.

• TrySubscribeOnServer returns false if the server isn't connected, and makes the subscription automatically once the server connection is established.

With these methods, you don't need to worry about whether there's a connection to the server at the time of the method call, making it easier to handle connection issues in your code.