[英]Async HTTP Server receiving spurious request
在此示例之后,我將同步HTTP服務器(使用.NET的HttpListener)轉換為異步。 它可以工作,但是對於我從Google Chrome瀏覽器發出的每個請求,無論是在地址欄上按Enter還是按F5鍵,我都會收到兩個請求。 第一個被完美地處理,並且響應在瀏覽器中呈現良好。
但是,第二個請求(甚至不應該出現)都具有一個空查詢字符串(我的服務器是控制台應用程序,因此我使用Console.WriteLine
看到了所有這些情況)。
當服務器處於同步狀態時,這一切都沒有發生,因此在移至異步模型時,我一定搞砸了。
這是代碼:
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 );
}
}
}
}
似乎只有在響應只是一堆字節時才會發生這種情況(在這種情況下代表jpeg圖像)。 如果不是直接在地址欄中輸入http請求,而是打開這樣的HTML頁面...
<html>
<head/>
<body>
<img src="http://localhost:serverPort/queryParametersGoHere" />
</body>
</html>
...我的服務器僅收到一個請求。 (我對端口和參數進行了匿名處理;在上面顯示為queryParametersGoHere,實際上我有?param1=value1¶m2=value2
,等等。
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