25

我在经典 ASP 中有以下片段，用于发送命令并通过 SSL 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，在调用 GetRequestStream 时，我不断收到带有消息的 WebException"The remote server returned an error: (502) Bad Gateway."

起初我认为这与 SSL 证书验证有关。所以我添加了这一行：

ServicePointManager.CertificatePolicy = new AcceptAllCertificatePolicy();

在哪里

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

而且我不断收到相同的 502 错误。有任何想法吗？

4

5 回答 5

36

读取错误响应的实体主体。它可能暗示正在发生的事情。

执行此操作的代码如下：

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全部内容。

于 2010-01-29T19:57:46.320 回答
27

在这个帮助下，我得到了问题的更详细描述：代理返回消息：“用户代理无法识别。” 所以我手动设置。此外，我将代码更改为使用GlobalProxySelection.GetEmptyWebProxy ()，如此处所述。最终的工作代码包含在下面。

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;
}
于 2010-02-01T05:11:52.643 回答
2

这发生在我身上，因为如果 Java 应用程序没有及时响应，远程计算机上的 Java 代理会超时请求，从而使 .NET 默认超时有点无用。以下代码循环遍历所有异常并写出帮助我确定它实际上来自代理的响应：

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);
}

来自代理的响应正文如下所示：

<!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>
于 2017-07-24T12:49:30.047 回答
2

缺少用户代理

例如：request.UserAgent =“Mozilla/4.0（兼容；MSIE 7.0；Windows NT 5.1）”；

于 2015-12-28T11:36:39.427 回答
1

Web 服务的 wsdl 可能正在与域名和 SSL 证书“争论”。IIS 将使用 IIS 注册域名（默认情况下是本地域上的机器名，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。

于 2010-01-29T03:13:57.917 回答