Meaning of PORTS column of Docker container ls-CodePudding

I'm getting this value on the PORTS column of a docker container ls entry (a container for a react app served by Nginx):

PORTS
80/tcp, 0.0.0.0:40000->40000/tcp, :::40000->40000/tcp

I know the second part is IPv4 mapping and the third is IPv6. I don't understand the meaning of the 80/tcp, but I think it's what really makes the app accessible from the internet, because if I use mapping "80:80" it works, but now with "40000:40000" it doesn't.

My project has a structure like this, so it can build multiple projects at once with compose:

|
|- client (a React app)
|  |- Dockerfile-client
|- .env.prod
|- docker-compose.yml

The docker-compose.yml looks like this:

version: '3.7'
services:
  client:
    build:
      dockerfile: ./client/Dockerfile-client
      context: ./ # so the .env.prod file can be used by React
    container_name: client
    env_file:
      - .env.prod # enabled to apply CLIENT_PORT var to Dockerfile-client
    ports:
      - "${CLIENT_PORT}:${CLIENT_PORT}"
  # others

All the variables are defined in .env.prod (CLIENT_PORT is 40000), and I run compose like `docker compose --env-file .env.prod up", and it doesn't bring errors.

Here's the Dockerfile that builds the client container:

# build env
FROM node:13.13-alpine as build
WORKDIR /app
COPY ./client/package*.json ./
RUN npm ci
COPY ./client/ ./
COPY ./.env.prod ./
RUN mv ./.env.prod ./.env
RUN npm run build

# production env
FROM nginx:stable-alpine
COPY --from=build /app/build /usr/share/nginx/html
EXPOSE ${CLIENT_PORT}
CMD ["nginx", "-g", "daemon off;"]

It would all work fine if I mapped "80:80", but my problem is how is that 80/tcp there in the ls output when there's no "80" to be seen in the files? Might it be because of Nginx?

CodePudding user response：

80/tcp is from nginx which listens by default on this port.

Correct port mapping in this case will be 4000:80

If you want nginx to listen on other port like 4000 update listen parameter in nginx.conf file to that port

http {
    server {
        listen 4000;

        }
}

And then use port mapping as 4000:4000