I am running s1300 with firmware version 3.029. It seems that adding port forward rule works from WAN, however when I use my WAN IP and this port from within LAN it does not work, just timeouts.
It appears to me that the the rules go to the chain GL_SPEC_FORWARDING that is part of PREROUTING chain. For this to work for LAN clients it would be required to also add chain/rules to the FORWARD chain, as this is what is used when traffic originates from within LAN/bridges.
@alzhao could you please look into it? Thanks.