code: static String getUserIdentifier(IoSession session) {
          boolean isAcceptor = isAcceptor(session);
          SocketAddress hostPortAddress = isAcceptor ? session.getRemoteAddress() : session.getLocalAddress();
          SocketAddress identityAddress = isAcceptor ? session.getLocalAddress() : session.getRemoteAddress();
          String identity = resolveIdentity(identityAddress, (IoSessionEx)session);
          String hostPort = getHostPort(hostPortAddress);
          return identity == null ? hostPort : format("%s %s", identity, hostPort);
      }
docs: Get a suitable identification for the user. For now this just consists of the TCP endpoint.
  the HTTP-layer auth principal, etc.
  @param session
  @return