Ping/Pong Messaging with TCP

To show off some of the messaging, let's just build a very simple "Ping/Pong" example that will exchange messages between two small .NET processes.

First off, I'm going to build out a very small shared library just to hold the messages we're going to exchange:

public class Ping
{
    public int Number { get; set; }
}

public class Pong
{
    public int Number { get; set; }
}

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And next, I'll start a small Pinger service with the dotnet new worker template. There's just three pieces of code, starting with the boostrapping code:

using Messages;
using Oakton;
using Pinger;
using Wolverine;
using Wolverine.Transports.Tcp;

return await Host.CreateDefaultBuilder(args)
    .UseWolverine(opts =>
    {
        // Using Wolverine's built in TCP transport

        // listen to incoming messages at port 5580
        opts.ListenAtPort(5580);

        // route all Ping messages to port 5581
        opts.PublishMessage<Ping>().ToPort(5581);

        // Registering the hosted service here, but could do
        // that with a separate call to IHostBuilder.ConfigureServices()
        opts.Services.AddHostedService<Worker>();
    })
    .RunOaktonCommands(args);

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and the Worker class that's just going to publish a new Ping message once a second:

using Messages;
using Wolverine;

namespace Pinger;

public class Worker : BackgroundService
{
    private readonly ILogger<Worker> _logger;
    private readonly IMessageBus _bus;

    public Worker(ILogger<Worker> logger, IMessageBus bus)
    {
        _logger = logger;
        _bus = bus;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        var pingNumber = 1;

        while (!stoppingToken.IsCancellationRequested)
        {
            await Task.Delay(1000, stoppingToken);
            _logger.LogInformation("Sending Ping #{Number}", pingNumber);
            await _bus.PublishAsync(new Ping { Number = pingNumber });
            pingNumber++;
        }
    }
}

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and lastly a message handler for any Pong messages coming back from the Ponger we'll build next:

using Messages;

namespace Pinger;

public class PongHandler
{
    public void Handle(Pong pong, ILogger<PongHandler> logger)
    {
        logger.LogInformation("Received Pong #{Number}", pong.Number);
    }
}

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Okay then, next let's move on to building the Ponger application. This time I'll use dotnet new console to start the new project, then add references to our Messages library and Wolverine itself. For the bootstrapping, add this code:

using Microsoft.Extensions.Hosting;
using Oakton;
using Wolverine;
using Wolverine.Transports.Tcp;

return await Host.CreateDefaultBuilder(args)
    .UseWolverine(opts =>
    {
        // Using Wolverine's built in TCP transport
        opts.ListenAtPort(5581);
    })
    .RunOaktonCommands(args);

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And a message handler for the Ping messages that will turn right around and shoot a Pong response right back to the original sender:

using Messages;
using Microsoft.Extensions.Logging;
using Wolverine;

namespace Ponger;

public class PingHandler
{
    public ValueTask Handle(Ping ping, ILogger<PingHandler> logger, IMessageContext context)
    {
        logger.LogInformation("Got Ping #{Number}", ping.Number);
        return context.RespondToSenderAsync(new Pong { Number = ping.Number });
    }
}

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public static class PingHandler
{
    // Simple message handler for the PingMessage message type
    public static ValueTask Handle(
        // The first argument is assumed to be the message type
        PingMessage message,

        // Wolverine supports method injection similar to ASP.Net Core MVC
        // In this case though, IMessageContext is scoped to the message
        // being handled
        IMessageContext context)
    {
        AnsiConsole.Write($"[blue]Got ping #{message.Number}[/]");

        var response = new PongMessage
        {
            Number = message.Number
        };

        // This usage will send the response message
        // back to the original sender. Wolverine uses message
        // headers to embed the reply address for exactly
        // this use case
        return context.RespondToSenderAsync(response);
    }
}

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If I start up first the Ponger service, then the Pinger service, I'll see console output like this from Pinger:

info: Pinger.Worker[0]
      Sending Ping #11
info: Pinger.PongHandler[0]
      Received Pong #1
info: Wolverine.Runtime.WolverineRuntime[104]
      Successfully processed message Pong#01817277-f692-42d5-a3e4-35d9b7d119fb from tcp://localhost:5581/
info: Pinger.PongHandler[0]
      Received Pong #2
info: Wolverine.Runtime.WolverineRuntime[104]
      Successfully processed message Pong#01817277-f699-4340-a59d-9616aee61cb8 from tcp://localhost:5581/
info: Pinger.PongHandler[0]
      Received Pong #3
info: Wolverine.Runtime.WolverineRuntime[104]
      Successfully processed message Pong#01817277-f699-48ea-988b-9e835bc53020 from tcp://localhost:5581/
info: Pinger.PongHandler[0]

and output like this in the Ponger process:

info: Ponger.PingHandler[0]
      Got Ping #1
info: Wolverine.Runtime.WolverineRuntime[104]
      Successfully processed message Ping#01817277-d673-4357-84e3-834c36f3446c from tcp://localhost:5580/
info: Ponger.PingHandler[0]
      Got Ping #2
info: Wolverine.Runtime.WolverineRuntime[104]
      Successfully processed message Ping#01817277-da61-4c9d-b381-6cda92038d41 from tcp://localhost:5580/
info: Ponger.PingHandler[0]
      Got Ping #3