# Port Forwarding FAQ

Transmission Help

# Why do I see a red dot and "Port is closed"?

You haven't port forwarded correctly. Port forwarding opens a port in your firewall or router so that incoming connections from the outside world can be made with Transmission.

# Why do I need to Port Forward?

Transmission uses a single port for all the torrents you are downloading. If the port has not been opened (ie forwarded) that means only you can make connections to others in the swarm. If the port is forwarded, others can connect to you, thus increasing the potential number of people connected to you, and more importantly increasing the speed of your download.

# How do I Port Forward?

- If you have an Apple Airport, or a UPnP compatible router, Transmission can map its port automatically. Most routers manufactured since 2001 have this feature.
  1. Open Transmission.
  2. Go to Preferences >> Network, and check 'Automatically map port'.
  3. You should see a success notification and green dots.

  If you get a red dot and the message 'Error mapping port', click here.

- If you don't have a compatible router, it is simple to forward Transmission's port manually. For instructions click here.
- If you don't use a router, that is, your modem is directly connected to your computer, you'll need to open Transmission's port in the Mac OS X firewall. For instructions click here.
  Keep in mind that many DSL modems also function as routers, and hence port forwarding as per above may still be necessary, even though your computer is directly connected to the modem.
  NB: it is highly recommended you enable the Mac OS X firewall if you are not using a router.

# How do I know if I've done it right?

1. Open Transmission.
2. Go to Preferences >> Network.
3. Check the notification next to 'Incoming TCP Port'.

- If you get a green dot and 'Port is Open' then you have successfully port forwarded!
- If you get a red dot and the message 'Port is Stealth' or 'Port is Closed' then you haven't forwarded correctly.
  NB: If Transmission has successfully mapped the port automatically, but the notification still indicates 'Closed/Stealth' click here.