HTTPS webservice call: Unexpected error occurred on receive

    protected str callCOM(str _type, str _httpAddress)
    {
        str                 ret;

        System.Net.HttpWebRequest       request;
        System.Net.HttpWebResponse      response;
        System.IO.Stream                streamstr,responsestr;
        System.IO.StreamReader          streamReader;
        System.Net.WebHeaderCollection  httpHeader;
        System.Byte[]                   bytes;
        CLRObject                       clrObj;

        new InteropPermission(InteropKind::ClrInterop).assert();

        System.Net.ServicePointManager::set_SecurityProtocol(System.Net.SecurityProtocolType::Tls);
                       
        clrObj = System.Net.WebRequest::CreateHttp(_httpAddress);
        request = clrObj;
        request.set_Method(_type);
        request.set_ContentType('application/xml; charset=utf-8');
        request.set_KeepAlive(false);
        request.set_Timeout(5000);
        request.set_ContentLength(0);

        httpHeader = request.get_Headers();
        httpHeader.Add('Authorization','Bearer '+B2bParameters::find().Password);

        if (_type!='GET')
        {
            bytes = System.Text.Encoding::get_UTF8().getBytes(xml.getText());
            request.set_ContentLength(bytes.get_Length());

            streamstr = request.GetRequestStream();
            streamstr.Write(bytes,0,bytes.Get_Length());
        }
        else
        {
            response = request.GetResponse();
            responsestr = response.GetResponseStream();
            streamReader = new System.IO.StreamReader(responsestr);
            ret = streamReader.ReadToEnd();
        }
        CodeAccessPermission::revertAssert();
 
        return ret;
    }