Simple HTTP web server

Concepts

• Use Deno’s integrated HTTP server to run your own web server.

Overview

With just a few lines of code you can run your own HTTP web server with control over the response status, request headers and more.

Sample web server

In this example, the user-agent of the client is returned to the client:

webserver.ts:

// Start listening on port 8080 of localhost.
const server = Deno.listen({ port: 8080 });
console.log(`HTTP webserver running.  Access it at:  http://localhost:8080/`);
// Connections to the server will be yielded up as an async iterable.
for await (const conn of server) {
  // In order to not be blocking, we need to handle each connection individually
  // without awaiting the function
  serveHttp(conn);
}
async function serveHttp(conn: Deno.Conn) {
  // This "upgrades" a network connection into an HTTP connection.
  const httpConn = Deno.serveHttp(conn);
  // Each request sent over the HTTP connection will be yielded as an async
  // iterator from the HTTP connection.
  for await (const requestEvent of httpConn) {
    // The native HTTP server uses the web standard `Request` and `Response`
    // objects.
    const body = `Your user-agent is:\n\n${
      requestEvent.request.headers.get(
        "user-agent",
      ) ?? "Unknown"
    }`;
    // The requestEvent's `.respondWith()` method is how we send the response
    // back to the client.
    requestEvent.respondWith(
      new Response(body, {
        status: 200,
      }),
    );
  }
}

Then run this with:

deno run --allow-net webserver.ts

Then navigate to http://localhost:8080/ in a browser.

Using the std/http library

ℹ️ Since the stabilization of native HTTP bindings in ^1.13.x, std/http now supports both a native HTTP server and legacy JavaScript HTTP server from ^0.107.0. The legacy server module is now deprecated, and is planned to be removed in a future release.

webserver.ts:

import { listenAndServe } from "https://deno.land/std@$STD_VERSION/http/server.ts";
const addr = ":8080";
const handler = (request: Request): Response => {
  let body = "Your user-agent is:\n\n";
  body += request.headers.get("user-agent") || "Unknown";
  return new Response(body, { status: 200 });
};
console.log(`HTTP webserver running. Access it at: http://localhost:8080/`);
await listenAndServe(addr, handler);

Then run this with:

deno run --allow-net webserver.ts

webserver_legacy.ts

import { serve } from "https://deno.land/std@$STD_VERSION/http/server_legacy.ts";
const server = serve({ port: 8080 });
console.log(`HTTP webserver running. Access it at: http://localhost:8080/`);
for await (const request of server) {
  let body = "Your user-agent is:\n\n";
  body += request.headers.get("user-agent") || "Unknown";
  request.respond({ status: 200, body });
}

Then run this with:

deno run --allow-net webserver_legacy.ts