I got an error: Web service callout failed: Unexpected element. Parser was expecting element 'http://schemas.xmlsoap.org/soap/envelope/:Envelope' but found ':HTML"

Can anyone tell me how I can generate some test code in Execute Anonymous to troubleshoot the following Callout SOAP request and response. The callout logic is very simple and it's about celsius to farenheit conversion. 

//Generated by wsdl2apex

public class ConverterWS {
    public class ConverterHttpSoap11Endpoint {
        public String endpoint_x = 'http://localhost:8080/Axis2WSTest/services/Converter.ConverterHttpSoap11Endpoint/';
        public Map<String,String> inputHttpHeaders_x;
        public Map<String,String> outputHttpHeaders_x;
        public String clientCertName_x;
        public String clientCert_x;
        public String clientCertPasswd_x;
        public Integer timeout_x;
        private String[] ns_map_type_info = new String[]{'http://wtp', 'ConverterWS'};
        public Double celsiusToFarenheit(Double celsius) {
            ConverterWS.celsiusToFarenheit_element request_x = new ConverterWS.celsiusToFarenheit_element();
            ConverterWS.celsiusToFarenheitResponse_element response_x;
            request_x.celsius = celsius;
            Map<String, ConverterWS.celsiusToFarenheitResponse_element> response_map_x = new Map<String, ConverterWS.celsiusToFarenheitResponse_element>();
            response_map_x.put('response_x', response_x);
            WebServiceCallout.invoke(
              this,
              request_x,
              response_map_x,
              new String[]{endpoint_x,
              'urn:celsiusToFarenheit',
              'http://wtp',
              'celsiusToFarenheit',
              'http://wtp',
              'celsiusToFarenheitResponse',
              'ConverterWS.celsiusToFarenheitResponse_element'}
            );
            response_x = response_map_x.get('response_x');
            return response_x.return_x;
        }
        public Double farenheitToCelsius(Double farenheit) {
            ConverterWS.farenheitToCelsius_element request_x = new ConverterWS.farenheitToCelsius_element();
            ConverterWS.farenheitToCelsiusResponse_element response_x;
            request_x.farenheit = farenheit;
            Map<String, ConverterWS.farenheitToCelsiusResponse_element> response_map_x = new Map<String, ConverterWS.farenheitToCelsiusResponse_element>();
            response_map_x.put('response_x', response_x);
            WebServiceCallout.invoke(
              this,
              request_x,
              response_map_x,
              new String[]{endpoint_x,
              'urn:farenheitToCelsius',
              'http://wtp',
              'farenheitToCelsius',
              'http://wtp',
              'farenheitToCelsiusResponse',
              'ConverterWS.farenheitToCelsiusResponse_element'}
            );
            response_x = response_map_x.get('response_x');
            return response_x.return_x;
        }
    }
    public class celsiusToFarenheit_element {
        public Double celsius;
        private String[] celsius_type_info = new String[]{'celsius','http://www.w3.org/2001/XMLSchema','float','0','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://wtp','true','true'};
        private String[] field_order_type_info = new String[]{'celsius'};
    }
    public class celsiusToFarenheitResponse_element {
        public Double return_x;
        private String[] return_x_type_info = new String[]{'return','http://www.w3.org/2001/XMLSchema','float','0','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://wtp','true','true'};
        private String[] field_order_type_info = new String[]{'return_x'};
    }
    public class farenheitToCelsiusResponse_element {
        public Double return_x;
        private String[] return_x_type_info = new String[]{'return','http://www.w3.org/2001/XMLSchema','float','0','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://wtp','true','true'};
        private String[] field_order_type_info = new String[]{'return_x'};
    }
    public class farenheitToCelsius_element {
        public Double farenheit;
        private String[] farenheit_type_info = new String[]{'farenheit','http://www.w3.org/2001/XMLSchema','float','0','1','false'};
        private String[] apex_schema_type_info = new String[]{'http://wtp','true','true'};
        private String[] field_order_type_info = new String[]{'farenheit'};
    }
}