What's the target group port for, when using Application Load Balancer + EC2 Container Service

Question

I'm trying to setup an ALB which listens on port 443, load balancing to ECS Docker containers on random ports, lets say I have 2 container instances of the same task definition, listening on port 30000 and 30001.

When I try to create a target group in the AWS EC2 Management console, there's a "port" input field with 1-65535 range. What number should I put there?

And when I try to create a new service in the AWS EC2 Container Service console, together with a new target group to connect to a existing ALB, there's no input field for a target group "port". After it's created, navigating to the EC2 console, the new target group has port "80". Do I have to listen on port 80? But the health check happens against the "traffic port", which is the container port, 30000 and 30001, so what's the point?

Answer 1

Turns out, when combined with ECS, the target group's port doesn't mean anything. You don't need to listen on that port.