Build on deno.land script found here https://dev.to/aralroca/learn-deno-chat-app-37f0

deno-simple-web-server.ts

/**
 * webserver.ts
 */
import { serve } from "https://deno.land/std@0.74.0/http/server.ts";

const server = serve({ hostname: "0.0.0.0", port: 8080 });
console.log(`HTTP webserver running.  Access it at:  http://localhost:8080/`);

for await (const request of server) {
  let bodyContent = "Your user-agent is:\n\n";
  bodyContent += request.headers.get("user-agent") || "Unknown";

  request.respond({ status: 200, body: bodyContent });
}

You can run this script from the terminal using
deno run --allow-net https://gist.githubusercontent.com/netsi1964/ee2ad2be6afee49cdcfa96cdc8c5ad68/raw/f49417d0344bfd0c0b5b135f28afe880cab3ef0c/deno-simple-web-server.ts