public String getApplicationProtocol() {
        return tlsPskServer != null ? tlsPskServer.getApplicationProtocol() : null;
    }
Returns the name of the current application-level protocol.
Returns:
the protocol name or null if application-level protocol has not been negotiated
zuul-core/src/main/java/com/netflix/zuul/netty/server/psk/TlsPskHandler.java