// add "http IHTTP in" as the last parameter to your service callback function
function serviceCallback(response string in, http IHTTP in)
  SysLib.writestdout(http.getResponse().headers["ip"]);

package client;

externalType HttpClient type JavascriptObject { relativePath = "client", externalName = "HttpClient" }
    function getIP() returns (string);
end

egl.defineClass(
  'client', 'HttpClient',
  {
    "getIP": function () {
      xhr = new XMLHttpRequest();
      protocol = "http";
      uri = protocol + ":" + "//localhost:8080/{someProj}/getIP.shtml"; 
      // this string manipulation isn't really needed, I'm using it
      // to avoid the warning about not being able to post links until
      // having posted more than 25 messages in this forum.
      xhr.open(uri, false);
      xhr.send("");
      ip = xhr.responseText;
      return ip;
    }
  }
);

package client;

import ...

handler Test type RUIHandler ...

    ...

    client HttpClient {};

    function start()
      someTextField.text = client.getIP();
    end

end

<clientInfo>
	<accept><!--#echo var='HTTP_ACCEPT'--></accept>
	<acceptCharset><!--#echo var='HTTP_ACCEPT_CHARSET'--></acceptCharset>
	<acceptLanguage><!--#echo var='HTTP_ACCEPT_LANGUAGE'--></acceptLanguage>
	<connection><!--#echo var='HTTP_CONNECTION'--></connection>
	<remoteAddress><!--#echo var='REMOTE_ADDR'--></remoteAddress>
	<remoteHost><!--#echo var='REMOTE_HOST'--></remoteHost>
	<remotePort><!--#echo var='REMOTE_PORT'--></remotePort> 
</clientInfo>

record ClientInfo{@XMLRootElement{name = "clientInfo"}}
    remoteAddress string;
    accept string;
    acceptCharset string;
    acceptLanguage string;
    connection string;
    remoteHost string;
    remotePort string;
end

interface IClientInfo

	function getClientInfo() returns (ClientInfo) {@GetRest {uriTemplate = "clientInfo.shtml", requestFormat = XML}};

end

...
function start()
   clientInfo IClientInfo? {@Resource};
   call clientInfo.getClientInfo()
      returning to someCallback
      onException someExceptionHandler;
end
...

interface IClientInfo

	function getClientInfo() returns (ClientInfo) {@GetRest {uriTemplate = "/clientInfo.shtml", requestFormat = XML}};

end

<clientInfo>
	<userAgent><!--#echo var='HTTP_USER_AGENT'--></userAgent>
	...
</clientInfo>