Question

我在本地计算机上创建一个简单的HTTP客户端/服务器应用程序，但我不知道为什么在服务器上触发ListenerCallback;但是，在客户端抛出“Web异常：无法连接到删除服务器”时，EndGetContext没有完成。有什么想法吗？这里是代码

    class Server
{
    static void Main(string[] args)
    {
        NonblockingListener(new string[] {"http://192.168.0.55:5432/"});
    }

    public static void NonblockingListener(string[] prefixes)
    {
        HttpListener listener = new HttpListener();
        foreach (string s in prefixes)
        {
            listener.Prefixes.Add(s);
        }
        listener.Start();
        IAsyncResult result = listener.BeginGetContext(new AsyncCallback(ListenerCallback), listener);     
        Console.WriteLine("Waiting for request to be processed asyncronously.");
        result.AsyncWaitHandle.WaitOne();
        Console.WriteLine("Request processed asyncronously.");
        listener.Close();
    }

    public static void ListenerCallback(IAsyncResult result)
    {
        HttpListener listener = (HttpListener)result.AsyncState;
        // Call EndGetContext to complete the asynchronous operation.

        HttpListenerContext context = listener.EndGetContext(result);
        HttpListenerRequest request = context.Request;
        Stream reader = request.InputStream;


        HttpListenerResponse response = context.Response;

        string responseString = "<HTML><BODY> Hello World!</BODY></HTML>";
        byte[] buffer = System.Text.Encoding.UTF8.GetBytes(responseString);

        response.ContentLength64 = buffer.Length;
        System.IO.Stream output = response.OutputStream;
        output.Write(buffer, 0, buffer.Length);

        output.Close();
    }


}


   class Client
{
    public static void Main()
    {
        // Create a request using a URL that can receive a post. 
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://192.168.0.55:5432");

        request.UserAgent = "linkToShare - HTTPWebRequest";
        request.Method = "POST";
        // Create POST data and convert it to a byte array.
        string postData = "data data data data.";
        byte[] byteArray = Encoding.UTF8.GetBytes(postData);
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = byteArray.Length;          
        Stream dataStream = request.GetRequestStream();
        dataStream.Write(byteArray, 0, byteArray.Length);
        dataStream.Close();
        WebResponse response = request.GetResponse();
        Console.WriteLine(((HttpWebResponse)response).StatusDescription);
        dataStream = response.GetResponseStream();
        StreamReader reader = new StreamReader(dataStream);
        string responseFromServer = reader.ReadToEnd();
        Console.WriteLine(responseFromServer);
        reader.Close();
        dataStream.Close();
        response.Close();
    }

}

Answer 1

您的代码的问题在于，您在服务器中调用EndGetContext方法，该方法将设置WaitHandle并在任何时间发送响应之前立即关闭服务器。

以下是对代码的轻微修改。

服务器：

class Program
{
    private static ManualResetEvent _waitHandle = new ManualResetEvent(false);

    static void Main()
    {
        NonblockingListener(new string[] { "http://+:5432/" });
    }

    public static void NonblockingListener(string[] prefixes)
    {
        using (var listener = new HttpListener())
        {
            foreach (string s in prefixes)
            {
                listener.Prefixes.Add(s);
            }
            listener.Start();
            var result = listener.BeginGetContext(new AsyncCallback(ListenerCallback), listener);
            Console.WriteLine("Waiting for request to be processed asyncronously.");

            // Block here until the handle is Set in the callback
            _waitHandle.WaitOne();
            Console.WriteLine("Request processed asyncronously.");
            listener.Close();
        }
    }

    public static void ListenerCallback(IAsyncResult result)
    {
        var listener = (HttpListener)result.AsyncState;
        var context = listener.EndGetContext(result);

        var response = context.Response;
        string responseString = "<HTML><BODY>Hello World!</BODY></HTML>";
        byte[] buffer = Encoding.UTF8.GetBytes(responseString);
        response.ContentLength64 = buffer.Length;
        response.OutputStream.Write(buffer, 0, buffer.Length);
        // Finished sending the response, now set the wait handle
        _waitHandle.Set();
    }
}

客户端：

class Program
{
    static void Main(string[] args)
    {
        using (var client = new WebClient())
        {
            client.Headers[HttpRequestHeader.UserAgent] = "linkToShare - HTTPWebRequest";
            var valuesToPost = new NameValueCollection
            {
                { "param1", "value1" },
                { "param2", "value2" },
            };
            var result = client.UploadValues("http://127.0.0.1:5432", valuesToPost);
            Console.WriteLine(Encoding.UTF8.GetString(result));
        }
    }
}

使用HttpWebRequest.GetRequestStream时无法连接到远程服务器

1 个答案: