MetaPubSub is an implementation of the publish/subscribe pattern - when the publisher and subscriber know nothing of each other but can exchange messages. It's fast, lightweight and beside basic functionality has some cool features:

• interprocess communication - messages can be sent between different processes and computers
• awaitable methods, for example, you can await Publish and wait until all subscribers have finished processing the message
• at least once delivery check - you can opt in to have an exception if no one subscribed to your message
• message filtering - you can define a predicate to subscribe only those messages you want to process
• timeout to wait for a subscriber - your message can be queued and wait until someone subscribed and processed it
• scheduling a message - your message can be queued and published after a time delay
• request-response pattern - send a message and wait for the response as a single awaitable method, without need to Subscribe/Unsubscribe to the response message
• cancellation token support - you can cancel scheduling or waiting for the message
• exceptions handling - all exceptions raised when a message processing by subscribers can be caught by the publisher as an AggregateException

MetaPipeServer and MetaPipeConnection are used to simplify inter-process communication using named pipes. The module utilizes NamedPipeServerStream and NamedPipeClientStream for message transmission. System.Text.Json is used for object serialization before sending. The main features of the module include:

• automatic connection recovery in case of disconnection
• transmission of strings, byte arrays, and arbitrary objects
• sending an arbitrary object and waiting for the response in a single method call.

PubSubPipe extends the capabilities of the MetaPubSub module by adding the ability to exchange messages between processes or computers.

StateMachine is a simple and easy to use state machine implementation. It is thread-safe and can be used in a concurrent environment. See the implementation of the MetaPipeConnection class for an example of usage.

To install the Meta.Lib run the following command:

PM> Install-Package Meta.Lib 

Note: this version has breaking changes. See migration guide.

• MetaPubSub has been separated into three modules - local PubSub, Pipe, and PubSubPipe. PubSub – is a local publisher/subscriber implementation. Pipe – is a wrapper on NamedPipeServerStream and NamedPipeClientStream to simplify interprocess communication. PubSubPipe – is a wrapper on both PubSub and Pipe which adds interprocess communication ability for PubSub via Pipe.
• Added ConcurrentStateMachine.
• Custom Logger implementation replaced with ILogger from the Microsoft.Extensions.Logging namespace.
• Removed IPubSubMessage interface. You don't need to derive your message classes from this interface anymore.
• Performance improvements.

Note: this version has breaking changes.

• IPubSubMessage.Timeout renamed to WaitForSubscriberTimeout.
• Added IPubSubMessage.ResponseTimeout - Time interval during which the response message must be received otherwise the TimeoutException will be thrown. Used in IMetaPubSub.Process() and IMetaPubSub.ProcessOnServer().
• Removed parameter millisecondsTimeout from IMetaPubSub.Process() and IMetaPubSub.ProcessOnServer(). Use IPubSubMessage.ResponseTimeout instead.
• Fixed bug: timeout in IMetaPubSub.Process() and IMetaPubSub.ProcessOnServer() always use it's default value of 5 sec.

• Added TryConnectToServer & TrySubscribeOnServer.
• Added a match predicate to SubscribeOnServer method.
• Added Connected/Disconnected built-in messages.
• Added a delegate method to create a pipe with non-default parameters.

• Interprocess communication implemented.