Docker - Why is this express.js container with an exposed/published port reject connections? (using boot2docker)

Question

I have a simple hello world express.js application inside of a docker container. It's set to run on port 8080 and the docker file exposes this port in the image. Additionally, I publish the port when I run the image. Yet when I try to make a simple curl request, the connection is rejected. Here's how I've setup this test:

My Dockerfile is pretty simple:

FROM node

ADD ./src /src
WORKDIR /src

# install your application's dependencies
RUN npm install

# replace this with your application's default port
EXPOSE 8080

# replace this with your main "server" script file
CMD [ "node", "server.js" ]

And inside my ./src directory I have a server.js file that looks like this:

var express = require('express');
var app = express();

app.get('/', function(req, res){
  res.send('Hello World');
});

var server = app.listen(8080, function() {
    console.log('Listening on port %d', server.address().port);
});

as well as a basic package.json which looks like this:

{
  "name": "hello-world",
  "description": "hello world test app",
  "version": "0.0.1",
  "private": true,
  "dependencies": {
    "express": "4.7.2"
  }
}

The image builds just fine:

→ docker build -t jimjeffers/hello-world .
Sending build context to Docker daemon 1.126 MB
Sending build context to Docker daemon 
Step 0 : FROM node
 ---> 6a8a9894567d
Step 1 : ADD ./src /src
 ---> 753466503fbf
Removing intermediate container 135dab70dfff
Step 2 : WORKDIR /src
 ---> Running in 12257ff3f990
 ---> 010ce4140cdc
Removing intermediate container 12257ff3f990
Step 3 : RUN npm install
 ---> Running in 1a9a0eb9d188
 ---> 5dc97c79281e
Removing intermediate container 1a9a0eb9d188
Step 4 : EXPOSE 8080
 ---> Running in abbaadf8709d
 ---> 9ed540098ed2
Removing intermediate container abbaadf8709d
Step 5 : CMD [ "node", "server.js" ]
 ---> Running in 63b14b5581cd
 ---> eababd51b50e
Removing intermediate container 63b14b5581cd
Successfully built eababd51b50e

And starts just fine:

→ docker run -P -d jimjeffers/hello-world
ee5024d16a679c10131d23c1c336c163e9a6f4c4ebed94ad4d2a5a66a64bde1d

→ docker ps
CONTAINER ID        IMAGE                           COMMAND                CREATED             STATUS              PORTS                     NAMES
ee5024d16a67        jimjeffers/hello-world:latest   node server.js         About an hour ago   Up 11 seconds       0.0.0.0:49158->8080/tcp   jovial_engelbart    
5d43b2dee28d        mongo:2.6                       /usr/src/mongo/docke   5 hours ago         Up 3 hours          27017/tcp                 some-mongo          

I can confirm the server is running inside the container:

→ docker logs ee5024d16a67
Listening on port 8080

But if I attempt to make a request the connection is refused.

→ curl -i 0.0.0.0:49158
curl: (7) Failed connect to 0.0.0.0:49158; Connection refused

Is there something I'm missing here? If I run the application without using docker it works as expected:

→ node src/server.js 
Listening on port 8080

→ curl -i 0.0.0.0:8080
HTTP/1.1 200 OK
X-Powered-By: Express
Content-Type: text/html; charset=utf-8
Content-Length: 11
ETag: W/"b-1243066710"
Date: Mon, 04 Aug 2014 05:11:58 GMT
Connection: keep-alive

Hello World

Answer 1

I found out the source of confusion. My machine is running on Mac OSX and thus I installed docker with boot2docker.

So again repeating the process:

→ docker run -P -d jimjeffers/hello-world
28431b32b93dbecaa2a8a5b129cbd36eebe8a90f4c20ab10735455d82fa9de37

→ docker ps
CONTAINER ID        IMAGE                           COMMAND                CREATED             STATUS              PORTS                     NAMES
28431b32b93d        jimjeffers/hello-world:latest   node server.js         2 hours ago         Up 9 minutes        0.0.0.0:49159->8080/tcp   stoic_franklin      
5d43b2dee28d        mongo:2.6                       /usr/src/mongo/docke   6 hours ago         Up 4 hours          27017/tcp                 some-mongo   

Finally, the trick was not to connect to my own machine but to curl from the VM's IP address:

→ boot2docker ip

The VM's Host only interface IP address is: 192.168.59.103

So I had finally achieved success when I curled the VM:

→ curl -i 192.168.59.103:49159
HTTP/1.1 200 OK
X-Powered-By: Express
Content-Type: text/html; charset=utf-8
Content-Length: 11
ETag: W/"b-1243066710"
Date: Mon, 04 Aug 2014 04:32:37 GMT
Connection: keep-alive

This is all explained well in detail on Docker's installation guide but I missed it as it was towards the end of the document.