Keep a Windows Service running without a timer

问题:

Currently the only examples of a Windows service in C# I have seen are where a timer runs through a method every x seconds - e.g. checking for file changes.

I'm wondering if it is possible (with example code if possible) to keep a Windows service running without a timer and instead just have a service listening for events - in the same way a console application can still listen for events and avoid closing with Console.ReadLine() without requiring a timer.

I am essentially looking for a way to avoid the x second delay between an event happening and an action being performed.

回答1:

A windows service does not need to create a timer to keep running. It can either establish a file watcher Using FileSystemWatcher to monitor a directory or start an asynchronous socket listener.

Here is a simple TPL based listener/responder without needing to dedicate a thread to the process.

private TcpListener _listener;

public void OnStart(CommandLineParser commandLine)
{
    _listener = new TcpListener(IPAddress.Any, commandLine.Port);
    _listener.Start();
    Task.Run((Func<Task>) Listen);
}

private async Task Listen()
{
    IMessageHandler handler = MessageHandler.Instance;

    while (true)
    {
        var client = await _listener.AcceptTcpClientAsync().ConfigureAwait(false);

        // Without the await here, the thread will run free
        var task = ProcessMessage(client);
    }
}

public void OnStop()
{
    _listener.Stop();
}

public async Task ProcessMessage(TcpClient client)
{
    try
    {
        using (var stream = client.GetStream())
        {
            var message = await SimpleMessage.DecodeAsync(stream);
            _handler.MessageReceived(message);
        }
    }
    catch (Exception e)
    {
        _handler.MessageError(e);
    }
    finally
    {
        (client as IDisposable).Dispose();
    }
}

Neither of these need a timer