Custom domains in Deno

Introduction

Custom domains let you use your own website address instead of a default one. This makes your site easier to find and looks more professional.

You want your website to have a unique and memorable web address.

You want to brand your website with a name you own.

You want to replace a default hosting URL with your own domain.

You want to improve trust by showing a custom domain to visitors.

You want to use email addresses linked to your website domain.

Syntax

Deno

import { serve } from "https://deno.land/std@0.177.0/http/server.ts";

serve(handler, { hostname: "your.custom.domain", port: 80 });

async function handler(req) {
  return new Response("Hello from your custom domain!");
}

The hostname option sets the domain or IP address your server listens on.

Make sure your DNS settings point your custom domain to your server's IP address.

Examples

Serve your app on the domain example.com at port 80 (default HTTP port).

Deno

serve(handler, { hostname: "example.com", port: 80 });

Serve your app on www.example.com at port 8080, useful for development or custom ports.

Deno

serve(handler, { hostname: "www.example.com", port: 8080 });

Serve on all network interfaces, allowing access via any domain or IP pointing to the server.

Deno

serve(handler, { hostname: "0.0.0.0", port: 80 });

Sample Program

This program starts a simple HTTP server that listens on mycustomdomain.com at port 80. When someone visits your site, they see the message "Welcome to my custom domain site!".

Remember to set your DNS records so that mycustomdomain.com points to your server's IP address.

Deno

import { serve } from "https://deno.land/std@0.177.0/http/server.ts";

const handler = (req: Request) => {
  return new Response("Welcome to my custom domain site!");
};

serve(handler, { hostname: "mycustomdomain.com", port: 80 });

Important Notes

DNS changes can take time to update (up to 48 hours).

Use HTTPS with custom domains for security; consider using a TLS certificate provider like Let's Encrypt.

Make sure your server firewall allows traffic on the port you use (usually 80 for HTTP or 443 for HTTPS).

Summary

Custom domains let you use your own website address instead of a default URL.

Set the hostname option in Deno's serve to your domain name.

Update DNS records to point your domain to your server's IP address.

Practice

1. What is the main purpose of setting a custom domain in a Deno server?

easy

A. To increase the server's processing speed

B. To use your own website name instead of a generic address

C. To automatically update the server software

D. To enable debugging features in Deno

Solution

1. Step 1: Understand what a custom domain is

   A custom domain lets you use a personalized website name instead of a default or generic address.

2. Step 2: Identify the purpose in Deno context

   Setting a custom domain in Deno allows your server to respond to your own website name, making it easier for users to find your site.

3. Final Answer:

   To use your own website name instead of a generic address -> Option B

4. Quick Check:

   Custom domain = personalized website name [OK]

Hint: Custom domain means your own website name, not generic [OK]

Common Mistakes:

• Confusing custom domain with server speed
• Thinking it updates software automatically
• Assuming it enables debugging

2. Which of the following is the correct way to set a custom domain hostname in Deno's serve function?

easy

A. serve({ url: "mydomain.com" })

B. serve({ domain: "mydomain.com" })

C. serve({ hostname: "mydomain.com" })

D. serve({ host: "mydomain.com" })

Solution

1. Step 1: Recall Deno serve options

   The serve function accepts an option called hostname to set the domain name.

2. Step 2: Match the correct option key

   Only hostname is the correct key; others like domain, host, or url are invalid here.

3. Final Answer:

   serve({ hostname: "mydomain.com" }) -> Option C

4. Quick Check:

   Use hostname option in serve [OK]

Hint: Use 'hostname' option exactly in serve function [OK]

Common Mistakes:

• Using 'domain' or 'host' instead of 'hostname'
• Passing the domain as a string without key
• Confusing 'url' with hostname option

3. Given the following code snippet, what will be the hostname the server listens on?

import { serve } from "https://deno.land/std/http/server.ts";
serve(() => new Response("Hello"), { hostname: "example.com" });

medium

A. The server will throw a runtime error

B. The server listens on localhost only

C. The server listens on all IP addresses

D. The server listens on example.com domain

Solution

1. Step 1: Examine the hostname option

   The code sets hostname: "example.com" in the serve options.

2. Step 2: Understand hostname resolution and binding

   Deno resolves "example.com" to a public IP (93.184.216.34) via DNS. If the IP is assigned to the local machine's network interfaces, the server binds successfully and listens on that domain. Otherwise, it will throw a runtime error.

3. Step 3: Typical behavior

   Usually, binding to a hostname that resolves to a public IP not assigned locally will fail. But if the environment is configured properly (e.g., hosts file or network interface), it can succeed.

4. Final Answer:

   The server listens on example.com domain -> Option D

5. Quick Check:

   Hostname option sets server listening domain [OK]

Hint: Hostname option sets server listening domain [OK]

Common Mistakes:

• Thinking server listens directly on domain without IP resolution
• Assuming default localhost behavior
• Believing it falls back to all IPs

4. You set hostname: "mydomain.com" in your Deno server but users cannot reach your site. What is the most likely cause?

medium

A. You forgot to point your domain's DNS to your server's IP address

B. The serve function does not support custom domains

C. You must use host instead of hostname

D. Deno requires a special flag to enable custom domains

Solution

1. Step 1: Verify Deno serve supports hostname

   Deno's serve supports hostname option, so options B, C, and D are incorrect.

2. Step 2: Check DNS setup

   If users cannot reach the site, the domain's DNS likely does not point to the server's IP, blocking access.

3. Final Answer:

   You forgot to point your domain's DNS to your server's IP address -> Option A

4. Quick Check:

   DNS must point domain to server IP [OK]

Hint: Check DNS points domain to server IP if unreachable [OK]

Common Mistakes:

• Assuming serve lacks custom domain support
• Using wrong option key like 'host'
• Thinking Deno needs special flags for domains

5. You want to serve your Deno app on your custom domain "myapp.com" and also allow access via localhost for testing. Which setup correctly supports both?

hard

A. Set hostname to "0.0.0.0" to listen on all interfaces including domain and localhost

B. Set hostname to "myapp.com, localhost" in a single serve call

C. Run two servers: one with hostname "myapp.com" and one with hostname "localhost"

D. Use hostname "localhost" and rely on DNS to redirect "myapp.com"

Solution

1. Step 1: Understand hostname options

   Setting hostname to "0.0.0.0" makes the server listen on all network interfaces, including your domain and localhost.

2. Step 2: Evaluate other options

   Run two servers: one with hostname "myapp.com" and one with hostname "localhost" requires two servers which is inefficient; Set hostname to "myapp.com, localhost" in a single serve call is invalid syntax; Use hostname "localhost" and rely on DNS to redirect "myapp.com" relies on DNS redirect which does not work for localhost access.

3. Final Answer:

   Set hostname to "0.0.0.0" to listen on all interfaces including domain and localhost -> Option A

4. Quick Check:

   Use 0.0.0.0 to listen on all interfaces [OK]

Hint: Use 0.0.0.0 hostname to serve domain and localhost [OK]

Common Mistakes:

• Trying to list multiple hostnames in one serve call
• Running multiple servers unnecessarily
• Relying on DNS to redirect localhost