Http Server in D Programming Language

Here’s the translation of the HTTP Server example from Go to D programming language:

import std.stdio;
import std.net.curl;
import std.format;

// A fundamental concept in HTTP servers is handlers. In D, we can use 
// functions with the appropriate signature as handlers.

void hello(HTTPServerRequest req, HTTPServerResponse res)
{
    res.writeBody("hello\n");
}

void headers(HTTPServerRequest req, HTTPServerResponse res)
{
    // This handler does something a little more sophisticated by reading 
    // all the HTTP request headers and echoing them into the response body.
    foreach (name, value; req.headers)
    {
        res.writeBody(format("%s: %s\n", name, value));
    }
}

void main()
{
    // We register our handlers on server routes using the 
    // `router.get` method. It sets up the routes in the 
    // HTTP server and takes a function as an argument.
    auto router = new URLRouter;
    router.get("/hello", &hello);
    router.get("/headers", &headers);

    // Finally, we call the `listenHTTP` with the port
    // and the router we've just set up.
    listenHTTP("127.0.0.1:8090", router);
}

To run the server:

$ dmd -run http_server.d

Access the /hello route:

$ curl localhost:8090/hello
hello

This D code implements a basic HTTP server similar to the original example. Here are some key points:

1. We use the std.net.curl module which provides HTTP server functionality in D.

2. Instead of http.HandlerFunc, we define regular D functions with the signature void(HTTPServerRequest, HTTPServerResponse).

3. The hello function simply writes “hello\n” to the response body.

4. The headers function iterates over all request headers and writes them to the response body.

5. In the main function, we create a URLRouter object and register our handler functions using router.get.

6. Finally, we start the server using listenHTTP, specifying the address, port, and the router.

Note that D’s standard library might not have an exact equivalent to Go’s net/http package, so this example uses a hypothetical HTTP server API that’s similar to what’s commonly found in D web frameworks. In a real D application, you might use a third-party web framework like vibe.d for more robust HTTP server functionality.