Unable to connect to localhost port running docker image - docker

Question

I'm trying to run a basic HelloWorld express app on my localhost using docker.
Docker version: Docker version 19.03.13
Project structure:
my-project
src
index.js
Dockerfile
package.json
package-lock.json
Dockerfile:
# Use small base image with nodejs 10
FROM node:10.13-alpine
# set current work dir
WORKDIR /src
# Copy package.json, packge-lock.json into current dir
COPY ["package.json", "package-lock.json*", "./"]
# install dependencies
RUN npm install --production
# copy sources
COPY ./src .
# open default port
EXPOSE 3000
# Run app
CMD ["node", "index.js"]
package.json
{
"name": "knative-serving-helloworld",
"version": "1.0.0",
"description": "Simple hello world sample in Node",
"main": "index.js",
"scripts": {
"start": "node index.js"
},
"author": "",
"license": "Apache-2.0",
"dependencies": {
"express": "^4.16.4"
},
}
index.js
const express = require('express');
const app = express();
app.get('/', (req, res) => {
console.log('Hello world received a request.');
res.send(`Hello world!\n`);
});
const port = process.env.PORT || 3000;
app.listen(port, () => {
console.log('Hello world listening on port', port);
});
Here are the commands I'm running:
>> docker build --tag hello-world:1.0 . // BUILD IMAGE AND GET ID
>> docker run IMAGE_ID // RUN CONTAINER WITH IMAGE_ID
Image seems to build just fine:
And this is the result after I run the image:
But this is what I get when I hit localhost:3000
I'm very new to Docker. What am I doing wrong?

Answer 1

You need to publish your port 3000.
docker run -p 3000:3000 IMAGE_ID
Just exposing the port is not enough it needs to be mapped on the host's port too.

Answer 2

Use host 0.0.0.0
app.listen(port, '0.0.0.0' () => {
console.log('Hello world listening on port', port);
});
Also, You need to publish port 3000:
docker run -p 3000:3000 IMAGE_ID