Full Duplex

Run the solution. Two console applications start-up, Client and Server.

Code walk-through

Messages

Look at the messages in the Shared project:

public class RequestDataMessage :
    IMessage
{
    public Guid DataId { get; set; }
    public string String { get; set; }
}

public class DataResponseMessage :
    IMessage
{
    public Guid DataId { get; set; }
    public string String { get; set; }
}

The two classes here implement the NServiceBus IMessage interface, indicating they are messages. These classes only have properties, each with get and set access. The RequestDataMessage is sent from the client to the server, and the DataResponseMessage replies from the server to the client.

Client

The client console has an input loop:

while (true)
{
    var key = Console.ReadKey();
    Console.WriteLine();

    if (key.Key != ConsoleKey.Enter)
    {
        break;
    }
    var guid = Guid.NewGuid();
    Console.WriteLine($"Requesting to get data by id: {guid:N}");

    var message = new RequestDataMessage
    {
        DataId = guid,
        String = "String property value"
    };
    await messageSession.Send("Samples.FullDuplex.Server", message);
}

This code sends a message with a new Guid and a string value every time the 'Enter' key is pressed.

Server

When a RequestDataMessage arrives in the server queue, the bus dispatches it to the message handler found in the RequestDataMessageHandler.cs file in the Server project. The bus knows which classes to call based on the interface they implement.

public class RequestDataMessageHandler () :
    IHandleMessages<RequestDataMessage>

At start-up, the bus scans all assemblies and builds a dictionary indicating which classes handle which messages. So when a given message arrives in a queue, the bus knows which class to invoke.

The Handle method of this class contains this:

var response = new DataResponseMessage
{
    DataId = message.DataId,
    String = message.String
};

await context.Reply(response);

Finally, the bus replies with the response message. The bus knows to send the responses to where the message was sent from, every time it receives a message from the queue.

Open DataResponseMessageHandler.cs in the Client project and find a class whose signature looks similar to the message handler on the server:

class DataResponseMessageHandler() :
    IHandleMessages<DataResponseMessage>