I am trying to integrate Salesforce and Microsoft Dynamics GP service using WSDL (SOAP). However on invoking method from Salesforce, I am getting an exception as "System.CalloutException: IO Exception: External server did not return any content".

I have set the endpoint in Remote Site Setting in SFDC. For authentication, I have used Basic authentication and passing it in the "inputHttpHeaders_x" parameter as we don't have login or authorization nodes available in WSDL.

Any inputs on this issue will be helpful.

Thanks.