@Override
  public synchronized InetSocketAddress getListenerAddress() {
    if (listener == null) {
      return null;
    }
    return listener.getAddress();
  }
Return the socket (ip+port) on which the RPC server is listening to. May return null if the
listener channel is closed.
@return the socket (ip+port) on which the RPC server is listening to, or null if this
        information cannot be determined
hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/SimpleRpcServer.java