Creating a Simple HTTP Web Server

To set up a basic HTTP server using Deno's server module, you can utilize the following code snippet:

const server = serve({ hostname: "0.0.0.0", port: 8080 });

console.log(HTTP server running on port 8080);

for await (const request of server) {

const bodyContent = Your user-agent is: ${request.headers.get("user-agent") || "Unknown"};

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

}

In this example, we import the serve function to establish our HTTP server. The server listens for requests on the specified hostname and port. Within a for-await-of loop, we construct the response body by retrieving the user-agent from the request headers. We then send the response using the request.respond method.

To execute the script, run:

deno run --allow-net index.ts

Afterward, navigating to http://localhost:8080 should display:

Your user-agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.111 Safari/537.36

Creating a File Server

Setting up a file server with Deno is straightforward. You can achieve this by executing the following command:

Once running, visiting http://localhost:4507/ will reveal a list of files from the current directory.

Building a TCP Echo Server

You can also create a TCP echo server using the Deno.listen and Deno.copy methods. Here’s how:

const listener = Deno.listen({ port: 8080 });

console.log("listening on 0.0.0.0:8080");

for await (const conn of listener) {

Deno.copy(conn, conn);

}

This code listens on port 8080 and loops through incoming connections, echoing data back to the client.

Creating a Subprocess

Deno allows you to create subprocesses with the Deno.run method. For instance, to execute the command echo hello, you can use the following code:

const p = Deno.run({

cmd: ["echo", "hello"],

});

await p.status();

This command runs the echo statement and waits for it to finish. To allow subprocesses, ensure to include the --allow-run flag.

You can also manage subprocesses and handle their output. For example:

const fileNames = Deno.args;

const p = Deno.run({

cmd: [

"deno",

"run",

"--allow-read",

...fileNames,

],

stdout: "piped",

stderr: "piped",

});

const { code } = await p.status();

if (code === 0) {

const rawOutput = await p.output();

await Deno.stdout.write(rawOutput);

} else {

const rawError = await p.stderrOutput();

const errorString = new TextDecoder().decode(rawError);

console.log(errorString);

}

Deno.exit(code);

This example retrieves the status code of the subprocess, outputs the result if successful, and logs any errors if they occur.