Http Server in Racket

Here’s the translation of the HTTP server example from Go to Racket, formatted in Markdown suitable for Hugo:

Our HTTP server example demonstrates how to create a basic web server using Racket’s built-in web server functionality.

#lang racket

(require web-server/servlet
         web-server/servlet-env)

;; A fundamental concept in Racket's web server is
;; request handlers. A handler is a function that takes
;; a request and produces a response.

(define (hello request)
  ;; This handler simply responds with "hello\n"
  (response/output
   (lambda (out)
     (fprintf out "hello\n"))))

(define (headers request)
  ;; This handler does something more sophisticated by reading
  ;; all the HTTP request headers and echoing them into the response body.
  (response/output
   (lambda (out)
     (for ([(name value) (in-hash (request-headers/raw request))])
       (fprintf out "~a: ~a\n" name value)))))

;; We define our handlers and their corresponding URLs
(define-values (dispatch generate-url)
  (dispatch-rules
   [("hello") hello]
   [("headers") headers]))

;; Finally, we start the web server
(serve/servlet
 dispatch
 #:port 8090
 #:servlet-regexp #rx"")

To run the server:

$ racket http-server.rkt

You can then access the server:

$ curl localhost:8090/hello
hello

In this Racket version:

1. We use the web-server/servlet and web-server/servlet-env libraries to create our server.

2. Instead of http.HandlerFunc, we define regular functions that take a request and return a response.

3. The dispatch-rules function is used to map URLs to our handler functions, similar to http.HandleFunc in the original example.

4. We use serve/servlet to start the server, specifying the port and the dispatch function.

5. The response/output function is used to create responses, allowing us to write directly to the output stream.

6. For the headers handler, we use request-headers/raw to access the request headers and iterate over them using Racket’s for loop syntax.

This example demonstrates how to create a basic HTTP server in Racket, handling different routes and processing request headers.