通过SSL发送HttpWebRequest请求时出现错误502(Bad Gateway)

dldeef67  于 2023-10-19  发布在  其他
关注(0)|答案(5)|浏览(213)

我在经典ASP中有以下片段,用于通过SSL发送命令并检索响应:

Dim xmlHTTP
Set xmlHTTP = Server.CreateObject("Msxml2.ServerXMLHTTP.3.0")
xmlHTTP.open "POST", "https://www.example.com", False
xmlHTTP.setRequestHeader "Content-Type","application/x-www-form-urlencoded"
xmlHTTP.setRequestHeader "Content-Length", Len(postData)
xmlHTTP.Send postData
If xmlHTTP.status = 200 And Len(message) > 0 And Not Err Then
   Print xmlHTTP.responseText
End If

然后我使用这段代码作为参考,在c#中重新实现了请求:

private static string SendRequest(string url, string postdata)
{
   WebRequest rqst = HttpWebRequest.Create(url);
   // We have a proxy on the domain, so authentication is required.
   WebProxy proxy = new WebProxy("myproxy.mydomain.com", 8080);
   proxy.Credentials = new NetworkCredential("username", "password", "mydomain");
   rqst.Proxy = proxy;
   rqst.Method = "POST";
   if (!String.IsNullOrEmpty(postdata))
   {
       rqst.ContentType = "application/x-www-form-urlencoded";

       byte[] byteData = Encoding.UTF8.GetBytes(postdata);
       rqst.ContentLength = byteData.Length;
       using (Stream postStream = rqst.GetRequestStream())
       {
           postStream.Write(byteData, 0, byteData.Length);
           postStream.Close();
       }
   }
   ((HttpWebRequest)rqst).KeepAlive = false;
   StreamReader rsps = new StreamReader(rqst.GetResponse().GetResponseStream());
   string strRsps = rsps.ReadToEnd();
   return strRsps;
}

问题是,当调用GetRequestStream时,我不断收到一个WebException,消息为"The remote server returned an error: (502) Bad Gateway."
起初我以为这与SSL证书验证有关。所以我添加了这一行:

ServicePointManager.CertificatePolicy = new AcceptAllCertificatePolicy();

哪里

public class AcceptAllCertificatePolicy : ICertificatePolicy
{
    public bool CheckValidationResult(ServicePoint srvPoint, 
                                      System.Security.Cryptography.X509Certificate certificate,
                                      WebRequest request, 
                                      int certificateProblem)
    {
        return true;
    }
}

同样的502错误。有什么想法吗?

yhqotfr8

yhqotfr81#

读取错误响应的实体正文。它可能会对正在发生的事情有所暗示。
代码如下:

catch(WebException e)
{
if (e.Status == WebExceptionStatus.ProtocolError)
{
    WebResponse resp = e.Response;
    using(StreamReader sr = new StreamReader(resp.GetResponseStream()))
    {
         Response.Write(sr.ReadToEnd());
    }
}
}

这应该显示错误响应的完整内容。

kx5bkwkv

kx5bkwkv2#

在此帮助下,我对问题进行了更详细的描述:代理正在返回消息:“无法识别用户代理”,所以我手动设置。另外,我将代码更改为使用GlobalProxySelection.GetEmptyWebProxy(),如here所述。最后的工作代码包括在下面。

private static string SendRequest(string url, string postdata)
{
    if (String.IsNullOrEmpty(postdata))
        return null;
    HttpWebRequest rqst = (HttpWebRequest)HttpWebRequest.Create(url);
    // No proxy details are required in the code.
    rqst.Proxy = GlobalProxySelection.GetEmptyWebProxy();
    rqst.Method = "POST";
    rqst.ContentType = "application/x-www-form-urlencoded";
    // In order to solve the problem with the proxy not recognising the user
    // agent, a default value is provided here.
    rqst.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)";
    byte[] byteData = Encoding.UTF8.GetBytes(postdata);
    rqst.ContentLength = byteData.Length;

    using (Stream postStream = rqst.GetRequestStream())
    {
        postStream.Write(byteData, 0, byteData.Length);
        postStream.Close();
    }
    StreamReader rsps = new StreamReader(rqst.GetResponse().GetResponseStream());
    string strRsps = rsps.ReadToEnd();
    return strRsps;
}
ryhaxcpt

ryhaxcpt3#

我之所以会遇到这种情况,是因为如果Java应用程序没有及时响应,远程机器上的Java代理就会对请求进行超时,从而使.NET默认超时变得毫无用处。下面的代码循环遍历所有异常并写出响应,这有助于我确定它实际上来自代理:

static void WriteUnderlyingResponse(Exception exception)
{
    do
    {
        if (exception.GetType() == typeof(WebException))
        {
            var webException = (WebException)exception;
            using (var writer = new StreamReader(webException.Response.GetResponseStream()))
                Console.WriteLine(writer.ReadToEnd());
        }
        exception = exception?.InnerException;
    }
    while (exception != null);
}

来自代理的响应体看起来像这样:

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>502 Proxy Error</title>
</head><body>
<h1>Proxy Error</h1>
<p>The proxy server received an invalid
response from an upstream server.<br />
The proxy server could not handle the request <em><a href="/xxx/xxx/xxx">POST&nbsp;/xxx/xxx/xxx</a></em>.<p>
Reason: <strong>Error reading from remote server</strong></p></p>
</body></html>
ryhaxcpt

ryhaxcpt4#

UserAgent丢失
例如:

request.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)";
fd3cxomn

fd3cxomn5#

Web服务的wsdl可能正在与域名和SSL证书“争论”。IIS将使用IIS注册的域名(默认情况下是本地域上的计算机名,不一定是您的Web域)自动生成Web服务的WSDL。如果证书域与SOAP12地址中的域不匹配,您将收到通信错误。

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