code: public Request getRequest() {
      if (clientTransaction != null) {
        return clientTransaction.getRequest();
      }
  
      if (serverTransaction != null) {
        return serverTransaction.getRequest();
      }
  
      return null;
    }
docs: The user test program MAY call this method to view the javax.sip.message.Request object that
  created this transaction. However, knowledge of JAIN SIP API is required to interpret the
  Request object.
  
  @return Returns the javax.sip.message.Request object that created this transaction.