Picture of setup (RB450G): http://www.eqcprices.com/setup.JPG
The server is "athlon" (192.168.0.248) and I cannot seem to get port 3784 opened to allow clients to connect. I can connect locally through port 3784, so the issue must be with the configuration of the router.
/ip firewall nat add chain=dstnat protocol=tcp dst-port=3784 action=dst-nat to-address=192.168.0.248 to-ports=3784 in-interface=WAN
I am sure the issue is not with my above NAT rule, but rather something else.
I think the line is correct and it should work. But it seems from the picture that the "to-address=192.168.0.248" was not recognized. try to make a /ip firewall nat print and check
Moreover, if your firewall is set up to block outside traffic not initiated from inside i.e. block all new connections from wan side the you need of course to put in a rule in your filter / forward chain to accept traffic to 3784
something like this
chain=forward action=accept protocol=tcp dst-port=3784
and the rule must be placed in the forward chain before all new connections are dropped.