code: public void addTransportListener(JingleTransportListener li) {
          for (ContentNegotiator contentNegotiator : contentNegotiators) {
              if (contentNegotiator.getTransportNegotiator() != null) {
                  contentNegotiator.getTransportNegotiator().addListener(li);
              }
          }
      }
docs: Add a listener for transport negotiation events.
  
  @param li
  The listener