The last post on this thread was 2012. Necro posting is frowned upon as Calibre changes twice monthly these days. The version features have bumped significantly
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Get it working Locally on your PC (local host)
Then try On your LAN from another device.
Neither of those need Router settings, only Firewall permissions.
(note: if both are WiFi devices, your AP/Router may need to allow 'peer' connections )