HTTP 500 Internal Server Error IOexception PI 7.3

Hi Expert,

We are using PI7.3. Now I have a asynchronous SOAP to IDoc scenario. When I send a soap message to PI which uses SOAP adapter, I got an error back saying "Server returned HTTP response code: 500 for URL.. IOException". I used to work in another company with PI 7.0. This scenario is very similar with my old one and I used similar codes in my java program to send SOAP message. It worked very well before. But now it does not work in PI 7.3. In my java program, I set up like this;

URL = PIHOST:port/XISOAPAdapter/MessageServlet?channel=:Business System:CCname
		        httpConn.setRequestProperty( "Content-Length",  String.valueOf( b.length ) );
		        httpConn.setRequestProperty("Content-Type","text/xml; charset=utf-8");
				  httpConn.setRequestProperty("SOAPAction",SOAPAction);
				  httpConn.setRequestProperty("Authorization", "Basic " + base64UserAndPasswd);
				
		        httpConn.setRequestMethod( "POST" );

I checked monitoring in PI . No message is coming. Can anyone tell me where is wrong? Is there any difference in SOAP adapter between PI 7.3 and PI 7.0? Where I can check more detail about the error. The log tells me the user login successfully. Thanks,

Charles