How to expose a Docker container to the internet on DigitalOcean?

Hey there 👋,

Great question! To make your Docker container accessible to the internet on your Droplet, you’ll need to expose the correct ports when you run the container. Here’s a bit more detail to get you going:

1. If your app is running on, let’s say, port 80 inside the container (for HTTP traffic), you’ll need to expose it to the outside world by mapping it to a port on your Droplet’s public IP. You can do this by adding the -p option to your Docker run command. For example:

   docker run -d -p 80:80 your-container-image
   

   This will map port 80 on your Droplet (the public IP) to port 80 inside your container, making your app accessible through the Droplet’s IP. If you’re running on a different port inside the container, just adjust the port mapping accordingly, e.g., -p 8080:80.

   Note that if you’re running your container on a different port (e.g., 8080), users will need to access your app via http://your-droplet-ip:8080. Also if your app is listening on a different port inside the container, you’ll need to adjust the -p option accordingly, eg. -p 3000:3000.

2. If you’re running multiple containers or want more control over how traffic is managed, you could set up Nginx as a reverse proxy. Nginx will listen for requests and forward them to the appropriate container. This is especially useful when you have multiple apps running on the same Droplet and want them all served via different paths or subdomains.

   Here’s an example of an Nginx configuration that forwards requests to your Docker container:

   server {
       listen 80;
       server_name yourdomain.com;
   
       location / {
           proxy_pass http://localhost:8080;
           proxy_set_header Host $host;
           proxy_set_header X-Real-IP $remote_addr;
           proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
           proxy_set_header X-Forwarded-Proto $scheme;
       }
   }
   

   You can also set up multiple locations in your Nginx config to handle multiple apps or services.

3. It’s super important to secure your web app with SSL (HTTPS), especially if you’re dealing with sensitive data. With Nginx, you can easily add SSL by using Let’s Encrypt, which provides free SSL certificates. You can follow this tutorial to install Let’s Encrypt and configure SSL for your Nginx setup.

On another note, if you haven’t already, be sure to check your firewall settings! You’ll want to make sure your Droplet’s firewall allows incoming traffic on ports 80 (HTTP) and 443 (HTTPS). You can manage this through DigitalOcean’s Cloud Firewalls, which make it easy to control inbound and outbound traffic.

Let me know how it goes or if you need any help with the Nginx setup, SSL configuration, or anything else!

- Bobby

And hey, if you’re new to Docker or want to dive deeper into using it, check out this free Docker eBook I wrote: Introduction to Docker eBook. It’s a great way to level up your container game!