我可以在不与服务器断开连接的情况下重用 HttpWebRequest 吗? [英] Can I reuse HttpWebRequest without disconnecting from the server?

问题描述

我正在尝试调试一个特定问题使用我的 ASP.NET 应用程序.客户端运行以下代码:

I'm trying to debug a specific issue with my ASP.NET application. The client runs the following code:

void uploadFile( string serverUrl, string filePath )
{
    HttpWebRequest request = (HttpWebRequest)HttpWebRequest.
        Create( serverUrl );
    CredentialCache cache = new CredentialCache();
    cache.Add( new Uri( serverUrl ), "Basic", new NetworkCredential( "User", "pass" ) );
    request.Credentials = cache;
    request.Method = "POST";
    request.ContentType = "application/octet-stream";
    request.Timeout = 60000;
    request.KeepAlive = true;

    using( BinaryReader reader = new BinaryReader( 
        File.OpenRead( filePath ) ) ) {

        request.ContentLength = reader.BaseStream.Length;
        using( Stream stream = request.GetRequestStream() ) {
            byte[] buffer = new byte[1024];
            while( true ) {
                int bytesRead = reader.Read( buffer, 0, buffer.Length );
                if( bytesRead == 0 ) {
                    break;
                }
                stream.Write( buffer, 0, bytesRead );
            }
        }
    }

     HttpWebResponse result = (HttpWebResponse)request.GetResponse();
     //handle result - not relevant
 }

和 Write() 抛出异常无法将数据写入传输连接:已建立的连接被主机中的软件中止."文本.我使用了 System.Net tracking 并发现当我发送带有 Content-Length 设置的请求时出现问题.

and Write() throws an exception with "Unable to write data to the transport connection: An established connection was aborted by the software in your host machine." text. I used System.Net tracing and found that something goes wrong when I send the request with Content-Length set.

特别是如果我在上面的代码中省略了 using 语句中的所有内容，服务器会立即回复 WWW-Authenticate 然后客户端用 重新发布请求WWW-Authenticate 一切正常，除了文件未上传并且请求稍后失败.

Specifically if I omit everything that is inside using statement in the code above the server promptly replies with WWW-Authenticate and then the client reposts the request with WWW-Authenticate and everything goes fine except the file in not uploaded and the request fails much later.

我想做以下事情:发送一个没有数据的请求，等待 WWW-Authenticate，然后用 WWW-Authenticate 和数据重复它.所以我尝试修改上面的代码:首先设置所有参数，然后调用 GetResponse()，然后发送，但是当我尝试设置 ContentLength 属性时，异常是抛出写入开始后无法设置此属性"文本.

I'd like to do the following: send an request without data, wait for WWW-Authenticate, then repeat it with WWW-Authenticate and data. So I tried to modify the code above: first set all the parameters, then call GetResponse(), then do sending, but when I try to set ContentLength property an exception is thrown with "This property cannot be set after writing has started" text.

所以 HttpWebRequest 似乎是不可重用的.

So HttpWebRequest seems to be non-reusable.

如何在不关闭连接的情况下重用它来重新发送请求?

How do I reuse it for resending the request without closing the connection?

推荐答案

您不会重复使用请求 - 顾名思义，它是一个请求.但是，如果您对同一主机发出多个请求，.NET 将默认重用底层网络连接.

You don't reuse a request - as the name suggests, it's one request. However, if you issue multiple requests for the same host, .NET will reuse the underlying network connection by default.

请注意，您确实需要处理 request.GetResponse 返回的 WebResponse - 否则底层基础架构不会知道您'实际上已经完成了，并且将无法重用连接.

Note that you do need to dispose of the WebResponse returned by request.GetResponse - otherwise the underlying infrastructure won't know that you're actually done with it, and won't be able to reuse the connection.

(顺便说一句，你为什么使用BinaryReader?直接使用File.OpenRead返回的流即可.)

(As an aside, why are you using BinaryReader? Just use the stream returned by File.OpenRead directly.)

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