[英]Async HTTP Server receiving spurious request
在此示例之后,我将同步HTTP服务器(使用.NET的HttpListener)转换为异步。 它可以工作,但是对于我从Google Chrome浏览器发出的每个请求,无论是在地址栏上按Enter还是按F5键,我都会收到两个请求。 第一个被完美地处理,并且响应在浏览器中呈现良好。
但是,第二个请求(甚至不应该出现)都具有一个空查询字符串(我的服务器是控制台应用程序,因此我使用Console.WriteLine
看到了所有这些情况)。
当服务器处于同步状态时,这一切都没有发生,因此在移至异步模型时,我一定搞砸了。
这是代码:
using System;
using System.Diagnostics;
using System.Net;
namespace MyWebServer{
internal static class MyHTTPServer {
private static int mPortNumber = 7091;
private static HttpListener mListener;
private static MyCustomHttpHandler mHttpHandler;
//Omitted some auxiliary methods to print stuff to Console,
//like WriteError and WriteRequestHeaderInformation
public static void Main( String[] pArg ) {
AppDomain.CurrentDomain.UnhandledException += UnhandledExceptionTrapper;
HttpHandler = new MyCustomHttpHandler();
mPortNumber = Convert.ToInt32( pArg[0] );
Console.WriteLine( "Starting the HttpListener on port:{0}", mPortNumber );
InitialiseListener();
Console.WriteLine( "Listener started on port: {0}, waiting for requests.", mPortNumber );
Console.WriteLine( "Listening. Press Enter to stop." );
Console.ReadLine();
if( mListener.IsListening )
mListener.Stop();
}
private static void InitialiseListener() {
try {
mListener = new HttpListener {
AuthenticationSchemes = AuthenticationSchemes.Basic
};
string prefix = string.Format( "http://+:{0}/", mPortNumber );
mListener.Prefixes.Add( prefix );
mListener.AuthenticationSchemes = AuthenticationSchemes.Anonymous;
mListener.Start();
mListener.BeginGetContext( RequestReceived, null );
} catch( Exception ex ) {
WriteError( ex.Message );
}
}
private static void RequestReceived( IAsyncResult result ) {
var timer = new Stopwatch();
Console.WriteLine( "---Request Received----" );
timer.Reset();
timer.Start();
//Retrieve context; on error, print message and wait for another request
HttpListenerContext context = null;
try {
context = mListener.EndGetContext( result );
} catch( HttpListenerException e ) {
WriteError( e.ToString() );
if( mListener.IsListening )
mListener.BeginGetContext( RequestReceived, null );
return;
}
//Process request and send response
mListener.BeginGetContext( RequestReceived, null );
try {
WriteRequestHeaderInformation( context );
CreateResponseDocument( context );
} catch( Exception ex ) {
WriteError( ex.Message );
}
Console.WriteLine( "----Request processed in {0} milliseconds ----", timer.ElapsedMilliseconds );
}
private static void CreateResponseDocument( HttpListenerContext pHttpListenerContext ) {
try {
byte[] htmlOutput = HttpHandler.ProcessRequest( pHttpListenerContext.Request.Url.LocalPath.Replace( "/", "" ), pHttpListenerContext.Request.Url.Query.Replace( "?", "" ) );
if( htmlOutput != null && pHttpListenerContext.Response.OutputStream.CanWrite ) {
pHttpListenerContext.Response.Headers.Add( "Access-Control-Allow-Origin", "*" );
//pHttpListenerContext.Response.ContentType = "image/jpg";
pHttpListenerContext.Response.ContentType = "text/plain";
pHttpListenerContext.Response.OutputStream.Write( htmlOutput, 0, htmlOutput.Length );
}
pHttpListenerContext.Response.Close();
} catch( Exception ex ) {
WriteError( ex.Message );
}
}
}
}
似乎只有在响应只是一堆字节时才会发生这种情况(在这种情况下代表jpeg图像)。 如果不是直接在地址栏中输入http请求,而是打开这样的HTML页面...
<html>
<head/>
<body>
<img src="http://localhost:serverPort/queryParametersGoHere" />
</body>
</html>
...我的服务器仅收到一个请求。 (我对端口和参数进行了匿名处理;在上面显示为queryParametersGoHere,实际上我有?param1=value1¶m2=value2
,等等。
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