I have encountered several dual sibling issues with running FL on two seperate 'puters on the same LAN and thus through the same Internet IP address. Seems like in one instant it worked without any changes to their geteway (some people call them routers but they do much more than just route!).

In another the gateway had to be configured for port translation. They figured out the port or range of ports one 'puter was using and had the gateway translate that to another port. What I saw on the FL server end was each sibling had an identical IP address but different ports.

I'm not sure of the exact mechanisms the network takes to have it work in one instant and not another. But I'm pretty positive the difference is you are both using the same IP address on the same port on the same server. If even just one was not the same you should have no problems.

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Earendil
SysAdmin of Boston Freelancer server
Server community website & forum: EarendilsPlace.net (server rules)