Question

在我构建的应用程序中，需要能够同时为多个客户端提供服务的Web服务器为此，我使用HttpListener对象。其Async种方法\事件BeginGetContext和EndGetContext 在委托方法中，有一个监听器再次开始监听的呼叫，它主要起作用。

提供的代码是我在这里和那里找到的混合代码，以及模拟数据处理瓶颈的延迟。

问题是，它只在最后一个连接服务之后开始管理下一个连接..对我没用。

public class HtServer {


    public void startServer(){
        HttpListener HL = new HttpListener();
        HL.Prefixes.Add("http://127.0.0.1:800/");
        HL.Start();
        IAsyncResult HLC = HL.BeginGetContext(new AsyncCallback(clientConnection),HL);   
    }

    public void clientConnection(IAsyncResult res){
        HttpListener listener = (HttpListener)res.AsyncState;
        HttpListenerContext context = listener.EndGetContext(res);
        HttpListenerRequest request = context.Request;
        // Obtain a response object.
        HttpListenerResponse response = context.Response;
        // Construct a response. 
        // add a delay to simulate data process
        String before_wait = String.Format("{0}", DateTime.Now);
        Thread.Sleep(4000);
        String after_wait = String.Format("{0}", DateTime.Now);
        string responseString = "<HTML><BODY> BW: " + before_wait + "<br />AW:" + after_wait + "</BODY></HTML>";
        byte[] buffer = System.Text.Encoding.UTF8.GetBytes(responseString);
        // Get a response stream and write the response to it.
        response.ContentLength64 = buffer.Length;
        System.IO.Stream output = response.OutputStream;
        // You must close the output stream.
        output.Write(buffer, 0, buffer.Length);
        output.Close();
        listener.BeginGetContext(new AsyncCallback(clientConnection), listener);
    }
}

修改

    private static void OnContext(IAsyncResult ar)
    {
        var ctx = _listener.EndGetContext(ar);
        _listener.BeginGetContext(OnContext, null);

        Console.WriteLine(DateTime.UtcNow.ToString("HH:mm:ss.fff") + " Handling request");

        var buf = Encoding.ASCII.GetBytes("Hello world");
        ctx.Response.ContentType = "text/plain";

        // prevent thread from exiting.
        Thread.Sleep(3000);
        // moved these lines here.. to simulate process delay
        ctx.Response.OutputStream.Write(buf, 0, buf.Length);
        ctx.Response.OutputStream.Close();
        Console.WriteLine(DateTime.UtcNow.ToString("HH:mm:ss.fff") + " completed");
    }

输出是 enter image description here

Answer 1

好。这是因为您在处理完第一个上下文后开始获取下一个上下文。不要这样做。直接获取下一个上下文：

public void clientConnection(IAsyncResult res){
    HttpListener listener = (HttpListener)res.AsyncState;
    HttpListenerContext context = listener.EndGetContext(res);

    //tell listener to get the next context directly.
    listener.BeginGetContext(clientConnection, listener);

    HttpListenerRequest request = context.Request;
    // Obtain a response object.
    HttpListenerResponse response = context.Response;
    // Construct a response. 
    // add a delay to simulate data process
    String before_wait = String.Format("{0}", DateTime.Now);
    Thread.Sleep(4000);
    String after_wait = String.Format("{0}", DateTime.Now);
    string responseString = "<HTML><BODY> BW: " + before_wait + "<br />AW:" + after_wait + "</BODY></HTML>";
    byte[] buffer = System.Text.Encoding.UTF8.GetBytes(responseString);
    // Get a response stream and write the response to it.
    response.ContentLength64 = buffer.Length;
    System.IO.Stream output = response.OutputStream;
    // You must close the output stream.
    output.Write(buffer, 0, buffer.Length);
    output.Close();
}

以下是我的示例代码，证明它有效（根据OP的请求更新）：

class Program
{
    private static HttpListener _listener;

    static void Main(string[] args)
    {
        _listener = new HttpListener();
        _listener.Prefixes.Add("http://localhost/asynctest/");
        _listener.Start();
        _listener.BeginGetContext(OnContext, null);

        Console.ReadLine();
    }

    private static void OnContext(IAsyncResult ar)
    {
        var ctx = _listener.EndGetContext(ar);
        _listener.BeginGetContext(OnContext, null);

        Console.WriteLine(DateTime.UtcNow.ToString("HH:mm:ss.fff") + " Handling request");

        var buf = Encoding.ASCII.GetBytes("Hello world");
        ctx.Response.ContentType = "text/plain";

        // simulate work
        Thread.Sleep(10000);

        ctx.Response.OutputStream.Write(buf, 0, buf.Length);
        ctx.Response.OutputStream.Close();


        Console.WriteLine(DateTime.UtcNow.ToString("HH:mm:ss.fff") + " completed");
    }
}

生成：

enter image description here

两个请求都开始直接处理。

为何上述代码有效

HTTP有一种叫做流水线的东西。这意味着通过同一连接接收的所有请求必须以相同的顺序获得响应。但是，内置的HttpListener似乎不支持流水线操作，而是在处理第二个请求之前完成第一个请求的响应。因此，确保通过新连接发送每个请求非常重要。

最简单的方法是在尝试代码时使用不同的浏览器。我这样做了，正如你所看到的那样，我的请求同时得到处理。

Answer 2

试试这个..

这将使用异步编码来确保没有阻塞。阻塞意味着线程休眠，这通常是程序倾向于“冻结”的方式。通过使用此代码，您可以运行非阻塞，这意味着它几乎不可能“冻结”应用程序。

public async Task handleClientConnection(HttpListener listener){
    HttpListenerContext context = await listener.GetContextAsync();
    var ret = handleClientConnection(listener);

    HttpListenerRequest request = context.Request;
    // Obtain a response object.
    HttpListenerResponse response = context.Response;
    // Construct a response. 
    // add a delay to simulate data process
    String before_wait = String.Format("{0}", DateTime.Now);
    await Task.Wait(4000);
    String after_wait = String.Format("{0}", DateTime.Now);
    string responseString = "<HTML><BODY> BW: " + before_wait + "<br />AW:" + after_wait + "</BODY></HTML>";
    byte[] buffer = System.Text.Encoding.UTF8.GetBytes(responseString);
    // Get a response stream and write the response to it.
    response.ContentLength64 = buffer.Length;
    using(System.IO.Stream output = response.OutputStream)
        output.Write(buffer, 0, buffer.Length);

    await ret;
}

public void startServer(){
    HttpListener HL = new HttpListener();
    HL.Prefixes.Add("http://127.0.0.1:800/");
    HL.Start();
    await handleClientConnection(HL);
}

如何使用HttpListener同时处理多个连接？

修改

2 个答案: