All API call are in server action so it run on server, so it should have access to RAILWAYPRIVATEDOMAIN right ?

Remember, your frontend's code will be running on a different computer in a different network so it won't be able to connect via the private network to the backend

so what's the use case of RAILWAYPRIVATEDOMAIN ?

it's meant for backend services to communicate among each other

using the private network for backend services to communicate has a lot of benefits, for example:

• Not exposed publicly, meaning better security

• Faster communication

• No egress costs

that's what I also understand so it should work in my case right ? since NextJS server action is call in the server (backend) so it should be able to communicate with django (backend) right ?

but when I try to use RAILWAYPRIVATEDOMAIN in http or https format, it doesn't work. It only work when I use RAILWAYPUBLICDOMAIN ?

ohh, if you're running it as a server action then yea sorry for my confusion

make sure you're also specifying the port when you're connecting to the private domain (unless it's running on port 80)

ohhh

a service (foo) running on port 3000's private connection would look like this:

• [http://foo.railway.internal:3000](http://foo.railway.internal:3000)

so RAILWAYPRIVATEDOMAIN does not forward port like RAILWAYPUBLICDOMAIN right ?

i see now, will make change now

yea, pretty much

HTTP uses port 80 by default and HTTPS uses port 443 by default
on the public domain Railway's proxy automatically bridges port 443 to your service's port
but on the private domain there is no proxy like that so you have to specify the port if it's not running on the default port

very clear now thank you

awesome, glad I could help 🙂

alright it work now. but to add a bit more RAILWAYPRIVATEDOMAIN use ipv6 so for it to work the django backend just need to also listen to ipv6.

oh true, glad you got it working!

!s