Transmission does not open ports in router if MiniDLNA is already running

[federicobt]

I have transmission set up to choose a random port and use UPnP to automatically forward that port in my router.

Some days ago I installed a DLNA server called MiniDLNA. It runs in port 8200 and it start when I turn the computer on, so whenever I start Transmission it is already running.

Now when I start transmission the port is still closed. I can confirm it in 3 ways:

• downloads are slow
• transmission says the port is closed
• the router does not show any forwarded port in the administration page

If I stop minidlna and then restart Transmission, the ports are opened as expected. After that I can start minidlna and both work perfectly.

I did not see anything interesting in neither minidlna's log nor transmission's log.

Any clue on why upnp port forwarding might not work if there's a dlna server already running? Is it a router bug, a transmission bug or just a upnp protocol limitation?

• Ubuntu 12.04 64 bits
• Router TP-LINK WR340GD
• MiniDLNA 1.1.0 (from this repo: ppa:stedy6/stedy-minidna)
• Transmission 2.51 (13280)

[livings124]

Transmission uses miniupnp (​http://miniupnp.tuxfamily.org/) for port forwarding. You'll have better luck at their site.