MassTransit and event versus command publishing

I'm new to MassTransit, and I miss something in my understanding.

Let's say I have a server farm were all nodes can do the same job. The application framework is CQRS's styled. That means I have two base kind of message to publish :

• Commands : must be handled by exactly one of the server, any of them (the first with job slot free)
• Events : must be handled by all servers

I've have build an extremely simple MassTransit prototype (a console application that is sending hello every X seconds).

In the API, I can see there is a "publish" method. How can I specify what kind of message it is (one versus all server)?

If I look a the "handler" configuration, I can specify the queue uri. If I specify the same queue for all hosts, all hosts will get the message, but I cannot limit the execution to only one server.

If I listen from a host dedicated queue, only one server will handle the messages, but I don't know how to broadcast the other kind of message.

Please help me to understand what I'm missing.

PS: if it cares, my messaging system is rabbitmq.

In order to test, I have create a common class library with this classes :

public static class ActualProgram
{
    private static readonly CancellationTokenSource g_Shutdown = new CancellationTokenSource();

    private static readonly Random g_Random = new Random();

    public static void ActualMain(int delay, int instanceName)
    {
        Thread.Sleep(delay);
        SetupBus(instanceName);

        Task.Factory.StartNew(PublishRandomMessage, g_Shutdown.Token);

        Console.WriteLine("Press enter at any time to exit");
        Console.ReadLine();
        g_Shutdown.Cancel();

        Bus.Shutdown();
    }

    private static void PublishRandomMessage()
    {
        Bus.Instance.Publish(new Message
        {
            Id = g_Random.Next(),
            Body = "Some message",
            Sender = Assembly.GetEntryAssembly().GetName().Name
        });

        if (!g_Shutdown.IsCancellationRequested)
        {
            Thread.Sleep(g_Random.Next(500, 10000));
            Task.Factory.StartNew(PublishRandomMessage, g_Shutdown.Token);
        }
    }

    private static void SetupBus(int instanceName)
    {
        Bus.Initialize(sbc =>
        {
            sbc.UseRabbitMqRouting();
            sbc.ReceiveFrom("rabbitmq://localhost/simple" + instanceName);
            sbc.Subscribe(subs =>
            {
                subs.Handler<Message>(MessageHandled);
            });
        });
    }

    private static void MessageHandled(Message msg)
    {
        ConsoleColor color = ConsoleColor.Red;
        switch (msg.Sender)
        {
            case "test_app1":
                color = ConsoleColor.Green;
                break;

            case "test_app2":
                color = ConsoleColor.Blue;
                break;

            case "test_app3":
                color = ConsoleColor.Yellow;
                break;
        }
        Console.ForegroundColor = color;
        Console.WriteLine(msg.ToString());
        Console.ResetColor();
    }

    private static void MessageConsumed(Message msg)
    {
        Console.WriteLine(msg.ToString());
    }
}

public class Message
{
    public long Id { get; set; }

    public string Sender { get; set; }

    public string Body { get; set; }

    public override string ToString()
    {
        return string.Format("[{0}] {1} : {2}" + Environment.NewLine, Id, Sender, Body);
    }
}

I have also 3 console applications that just run the ActualMain method :

internal class Program
{
    private static void Main(string[] args)
    {
        ActualProgram.ActualMain(0, 1);
    }
}