自定义多线程Http Server不是线程安全的

Question

There is a simple multi-threaded web server I wrote in C# (the part of the code):

  public class MyServer
    {
        private readonly HttpListener _listener = new HttpListener();
        private int  _dataId;
        public HttpServer(string prefix, string folder)
        {
            System.Threading.ThreadPool.SetMaxThreads(50, 1000);
            System.Threading.ThreadPool.SetMinThreads(50, 50);
            //........
        }

        public void Start()
        {
            _listener.Start();
            while (true)
             ThreadPool.QueueUserWorkItem(ProcessRequest, _listener.GetContext());
        }


        private void ProcessRequest(object obj)
        {
           //.....
        }


}

If a send the requests by browser (or whatever using only one main thread) then everything is OK. But if do it by the code below, then the server usually receives the same values for different requests:

Your thought?

-- EDIT --:

The simple question is, does using only local variables make me sure that my code is thread safe? And vise versa: if I'm using instance variables (not static, that's _dataId in my case ), must I "look after" them to make them thread safe (for instance, by lock keyword)?

Answer 1

The canonical way to use the HttpListener in a multithreaded fashion would be through the Begin/End async pattern, here is an example .

If your handler method is re-entrant, ie It does not depend on any instance state then chances are good that the code is thread-safe. Question is whether any classes, methods etc. That you use are also thread-safe.

Answer 2

You should start another thread, that will in cycle call GetContext, instead of queing the same context multiple time.

public void Start()
{
    _listener.Start();
    ThreadPool.QueueUserWorkItem(StartImpl);
}
public void StartImpl()
{
    while (true)
        ProcessRequest(_listener.GetContext());
}