How to Create HTTP Server in Deno: Simple Guide

In Deno, you create an HTTP server using the serve function from the std/http/server.ts module. You write an async function to handle requests and pass it to serve, which listens on a port and responds to incoming HTTP requests.

Syntax

To create an HTTP server in Deno, import serve from std/http/server.ts. Then call serve with an async function that receives a Request object and returns a Response object. Optionally, specify the port to listen on.

• import: brings in the serve function
• serve(): starts the server and listens for requests
• async handler: processes each request and returns a response

typescript

import { serve } from "https://deno.land/std@0.203.0/http/server.ts";

serve(async (req) => {
  return new Response("Hello from Deno HTTP server!", {
    status: 200,
    headers: { "content-type": "text/plain" },
  });
}, { port: 8000 });

Example

This example creates a simple HTTP server that listens on port 8000 and responds with a plain text greeting to every request.

typescript

import { serve } from "https://deno.land/std@0.203.0/http/server.ts";

console.log("HTTP server is running on http://localhost:8000/");

serve(async (req) => {
  return new Response("Hello from Deno HTTP server!", {
    status: 200,
    headers: { "content-type": "text/plain" },
  });
}, { port: 8000 });

Output

HTTP server is running on http://localhost:8000/

Common Pitfalls

Common mistakes when creating an HTTP server in Deno include:

• Not importing serve from the correct URL or version.
• Forgetting to make the handler function async when using asynchronous code.
• Not returning a proper Response object.
• Not specifying the port or using a port already in use.
• Running the server without the necessary permissions (use --allow-net flag).

Always run your server with deno run --allow-net your_file.ts to allow network access.

typescript

/* Wrong: Missing async and improper response */
import { serve } from "https://deno.land/std@0.203.0/http/server.ts";

serve((req) => {
  // This will cause an error because the handler is not async and no Response returned
  console.log(req.url);
});

/* Right: Async handler returning Response */
serve(async (req) => {
  return new Response("OK", { status: 200 });
}, { port: 8000 });

Quick Reference

Summary tips for creating HTTP servers in Deno:

• Import serve from std/http/server.ts with a fixed version.
• Use an async function to handle requests.
• Return a Response object with status and headers.
• Run with --allow-net permission.
• Specify the port in serve options.

Key Takeaways

Use the built-in serve function from Deno's standard library to create HTTP servers.

Always write an async handler function that returns a Response object.

Run your Deno server with --allow-net permission to enable network access.

Specify the port explicitly to avoid conflicts and clarify where the server listens.

Import serve from a fixed version URL to ensure stable and consistent behavior.