Error 502 (Bad Gateway) when sending a request with HttpWebRequest over SSL

c#, httpwebrequest, ssl, system.net.webexception

Solution

With the help of this I got a more detailed description of the problem: The proxy was returning the message: "The user agent is not recognized." So I set it manually. Also, I changed the code to use GlobalProxySelection.GetEmptyWebProxy(), as described here. The final working code is included below.

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;
}

Problem

I have the following snippet in classic ASP, to send a command and retrieve the response over SSL: ``` 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 ``` Then I used this code as a reference to reimplement the request in c#: ``` 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; } ``` The problem is, when calling GetRequestStream I keep getting a WebException with the message `"The remote server returned an error: (502) Bad Gateway."` At first I thought it had to do with the SSL certificate verification. So I added this line: ``` ServicePointManager.CertificatePolicy = new AcceptAllCertificatePolicy(); ``` Where ``` public class AcceptAllCertificatePolicy : ICertificatePolicy { public bool CheckValidationResult(ServicePoint srvPoint, System.Security.Cryptography.X509Certificate certificate, WebRequest request, int certificateProblem) { return true; } } ``` And I keep getting the same 502 error. Any ideas?

Original source

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