I had a similar error and when I checked the server logs - it was related to http server having encountered an unsupported http method in request. Due to this teh server returns an HTTP response that the SOAP client cannot handle ... hence Unexpected EOF in prolog
Below is a snippet my web-server log for tomcat "localhost.XXXX.log"
org.apache.tomcat.util.descriptor.web.SecurityConstraint.findUncoveredHttpMethods For security constraints with URL pattern [/services/*] only the HTTP methods [POST GET] are covered. All other methods are uncovered.
This gave following error on client side
com.ctc.wstx.exc.WstxEOFException: Unexpected EOF in prolog
In my case since I was downgrading a secured service to unsecured and my web.xml had following stray entry that was restricting GET and post with a security constraint and I wasnt sending needed security parameters in the request..
<security-constraint>
<web-resource-collection>
<web-resource-name>restricted web services</web-resource-name>
<url-pattern>/services/*</url-pattern>
<http-method>GET</http-method>
<http-method>POST</http-method>
</web-resource-collection>
I removed this constraint to get rid of this error :-)
In your case it may not related to security constraint - but for sure its related to server sending raw http response - Please check your server/ client configuration and ensure it sends appropriate http request that are liked by http server