@Override
    StanzaHandler createStanzaHandler(NettyConnection connection) {
        return new ServerStanzaHandler( XMPPServer.getInstance().getPacketRouter(), connection, directTLS);
    }
Enable / disable backup delivery of stanzas to the XMPP server itself when a stanza failed to be delivered on a
server-to-server connection. When disabled, stanzas that can not be delivered on the connection are discarded.
xmppserver/src/main/java/org/jivesoftware/openfire/nio/NettyServerConnectionHandler.java