.Net 5.0 和 6.0，后台服务不会像 MS 的样本那样停止

Question

In short I'm building a TCP server for a simple DB process. I looked at the MS samples for background service specifically the App.WorkerService.

So far so good, can run the service and it only starts the TCP server once per app instance.

Now I want to have the service stopped when a user, in the command window it is running, hits the [ESC]ape key on the keyboard.

Here is the Program.cs:

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace PostDataService
{
  public class Program
  {
    public static void Main(string[] args)
    {
      CreateHostBuilder(args).Build().Run();
    }

    public static IHostBuilder CreateHostBuilder(string[] args) =>
        Host.CreateDefaultBuilder(args)
            .ConfigureServices((hostContext, services) =>
            {
              services.AddHostedService<Worker>();
            });
  }
}

Here is the Worker class:

using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using System;
using System.Threading;
using System.Threading.Tasks;
using WatsonTcp;

namespace PostDataService
{
  public class Worker : BackgroundService
  {
    private readonly ILogger<Worker> _logger;
    private int _serverPort = 1701;
    private static WatsonTcpServer _Server;

    public Worker(ILogger<Worker> logger)
    {
      _logger = logger;
      _Server = new(null, _serverPort);
      _Server.Events.ClientConnected += ClientConnected;
      _Server.Events.ClientDisconnected += ClientDisconnected;
      _Server.Events.MessageReceived += MsgReceived;
      _Server.Start();
    }

    private void MsgReceived(object sender, MessageReceivedEventArgs args)
    {
      Console.WriteLine("Got Msg");
    }

    private void ClientDisconnected(object sender, DisconnectionEventArgs args)
    {
      throw new NotImplementedException();
    }

    private void ClientConnected(object sender, ConnectionEventArgs args)
    {
      throw new NotImplementedException();
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
      while (!stoppingToken.IsCancellationRequested)
      {
        _logger.LogInformation("Worker running at: {time} {threadid}", DateTimeOffset.Now, Thread.CurrentThread.ManagedThreadId );

        await Task.Delay(500, stoppingToken);
      }
      _Server.Stop();
    }
  }
}

So how would I get the stoppingToken.IsCancellationRequested set to true?

Answer 1

The shortcut to stop console application is Ctrl+C not Esc. If you still want Esc to be working you can do something like this:

IHost host = Host.CreateDefaultBuilder(args)
    .ConfigureServices(services =>
    {
        services.AddHostedService<Worker>();
    })
    .Build();

var hostTask = host.RunAsync();

// listen for Esc 
_ = Task.Run(async () =>
{
    ConsoleKeyInfo key;
    do
    {
        key = Console.ReadKey();
    }
    while (key.Key != ConsoleKey.Escape);
    await host.StopAsync();
});

await hostTask;

Also I recommend adding something like this in your Worker :

public override Task StopAsync(CancellationToken cancellationToken)
{ 
    _logger.LogInformation("stopping server");
    _Server.Stop();
    return Task.CompletedTask;  
}