My First Web Service Invocation

[hanane]

Hi,
I am trying to invoke my first Web Service but kept getting the same error msg: "failed attempting to read SOAP response from service. This is probably due to a communication error"

This is the WS description:

 
<?xml version="1.0" encoding="UTF-8"?>
<definitions name="HelloService"
    targetNamespace="http://dl.dropbox.com/u/2920864/HelloService.wsdl"
    xmlns:tns="http://dl.dropbox.com/u/2920864/HelloService.wsdl"
    xmlns="http://schemas.xmlsoap.org/wsdl/"
    xmlns:xsd="http://www.w3.org/2001/XMLSchema"
    xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/">
    <types/>
    <message name="Hello_hello">
        <part name="String_1" type="xsd:string"/>
    </message>
    <message name="Hello_helloResponse">
        <part name="result" type="xsd:string"/>
    </message>
    <portType name="Hello">
        <operation name="hello" parameterOrder="String_1">
            <input message="tns:Hello_hello"/>
            <output message="tns:Hello_helloResponse"/>
        </operation>
    </portType>
    <binding name="HelloBinding" type="tns:Hello">
        <soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="rpc"/>
        <operation name="hello">
            <soap:operation soapAction=""/>
            <input>
                <soap:body use="literal" namespace="http://hello.chap12.jboss.org/"/>
            </input>
            <output>
                <soap:body use="literal" namespace="http://hello.chap12.jboss.org/"/>
            </output>
        </operation>
    </binding>
    <service name="HelloService">
        <port name="HelloPort" binding="tns:HelloBinding">
            <soap:address location="http://dl.dropbox.com/u/2920864/HelloService.wsdl"/>
        </port>
    </service>
</definitions>

My code is validated, analyzed, but when I get to invoking it, I keep getting this error msg:
"failed attempting to read SOAP response from service. This is probably due to a communication error"
Do you have any idea about what should I change? the binding? the fact that I am hosting it in a public folder of my dropbox?

thanks for your time!