I have a piece of .NET code that is erroring out when it makes a call to HTTPWebRequest.GetRequestStream. Here is the error message:

The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel.

I've read a few things that suggest that I might need a certificate on the machine running the code, but i'm not sure if that's true or how to do it.

If I need to get a certificate, how do I do it?

Code:

        var request = (HttpWebRequest)HttpWebRequest.Create(requestUrl); //my url
        request.Method = StringUtilities.ConvertToString(httpMethod); // Set the http method GET, POST, etc.

        if (postData != null)
        {
            request.ContentLength = postData.Length;
            request.ContentType = contentType;
            using (var dataStream = request.GetRequestStream())
            {
                dataStream.Write(postData, 0, postData.Length);
            }
        }