Docker port forwarding question

[Ockingshay]

I've setup transmission and the default port in the image is 54321. I've specified it as 63334 and opened up the port in my router. I know the port is open as the tests from port checking websites shows its open. But in transmission, it reports it as closed. I can connect to peers no problem, but I thought it would be seamless, and it would just report it back as open.

 

Has anyone got transmission or any docker for that matter to report back an open port? The docker is in bridge mode with the default port (54321) mapped to 63334 on lan ip 192.168.0.3 with the corresponding port open on the router 192.168.0.3:63334.

 

Cheers

 

 

Edit: if I set it to host mode and then just specify port 63334 in transmissio. It shows it as open. I would expect using a bridge and mapping the correct port it would achieve the same result?

 

[BRiT]

The issue is to the docker containers they see their IP as completely different than the 192.x.y.z or 10.x.y.z that your unraid server has. They are run on a different network ip bridge.

[gfjardim]

Inside Docker, Transmission thinks it's on port 54321, so it uses a web service to probe that port and, since it's closed (you open 63334 instead), it will report  port 54321 as closed. Simple as that.

 

You have to sync your port in Port Maps or simple use "host network", which is a bit more insecure.

[Ockingshay]

The issue is to the docker containers they see their IP as completely different than the 192.x.y.z or 10.x.y.z that your unraid server has. They are run on a different network ip bridge.

 

Yes, that makes sense, but surely in the port mappings section, if i map the internal docker port of 54321 to the external unraid port of 63334, it should follow the correct path? Or if not, how do i find out what port the docker is looking for?

 

Inside Docker, Transmission thinks it's on port 54321, so it uses a web service to probe that port and, since it's closed (you open 63334 instead), it will report  port 54321 as closed. Simple as that.

 

You have to sync your port in Port Maps or simple use "host network", which is a bit more insecure.

 

I thought i had synced the ports in port maps. dockers shows 54321/tcp  <--> 192.168.0.3:63334. Is there another place i have to specify?

[Ockingshay]

and here is what is specified in the docker container settings:

[gfjardim]

By sync I mean 63334-> 63334

[Ockingshay]

cool, that seems to work.

 

Maybe not a question for you to answer, but what is the point of being able to map different ports if it doesn't allow a seamless path between docker and the real world?

 

thanks for your help though, it allows me to continue my setup.

[gfjardim]

cool, that seems to work.

 

Maybe not a question for you to answer, but what is the point of being able to map different ports if it doesn't allow a seamless path between docker and the real world?

 

thanks for your help though, it allows me to continue my setup.

 

Some services work fine with async port maps, like Couchpotato, NZBget, Sonarr etc, some don't, like Torrent/BTSync/Dropbox. The new Docker 1.5 will allow us to map port ranges, and that will make torrent with random ports easier to map.

 

 

[lionelhutz]

That type of mapping works fine when you only access the Docker via the mapped port. But, it won't work when the Docker is reporting it's port to the outside world because the port it's reporting doesn't work in the outside world.