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Web requests with HTTP#

Relevant example: shader


CrSFML provides a simple HTTP client class which you can use to communicate with HTTP servers. "Simple" means that it supports the most basic features of HTTP: POST, GET and HEAD request types, accessing HTTP header fields, and reading/writing the pages body.

If you need more advanced features, such as secured HTTP (HTTPS) for example, you're better off using a true HTTP library.

For basic interaction between your program and an HTTP server, it should be enough.


To communicate with an HTTP server you must use the SF::Http class.

http =

# or
http ="")

Note that setting the host doesn't trigger any connection. A temporary connection is created for each request.

The only other method in SF::Http, sends requests. This is basically all that the class does.

request =
# fill the request...
response = http.send_request(request)


An HTTP request, represented by the SF::Http::Request class, contains the following information:

  • The method: POST (send content), GET (retrieve a resource), HEAD (retrieve a resource header, without its body)
  • The URI: the address of the resource (page, image, ...) to get/post, relative to the root directory
  • The HTTP version (it is 1.0 by default but you can choose a different version if you use specific features)
  • The header: a set of fields with key and value
  • The body of the page (used only with the POST method)
request =
request.method = SF::Http::Request::Post
request.uri = "/index.html"
request.set_http_version(1, 1) # HTTP 1.1
request.set_field("From", "me")
request.set_field("Content-Type", "application/x-www-form-urlencoded")
request.body = "para1=value1&param2=value2"

response = http.send_request(request)

SFML automatically fills mandatory header fields, such as "Host", "Content-Length", etc. You can send your requests without worrying about them. SFML will do its best to make sure they are valid.


If the SF::Http class could successfully connect to the host and send the request, a response is sent back and returned to the user, encapsulated in an instance of the SF::Http::Response class. Responses contain the following members:

  • A status code which precisely indicates how the server processed the request (OK, redirected, not found, etc.)
  • The HTTP version of the server
  • The header: a set of fields with key and value
  • The body of the response
response = http.send_request(request)
puts "Status: #{response.status}"
puts "HTTP version: #{response.major_http_version}.#{response.minor_http_version}"
puts "Content-Type header: " + response.get_field("Content-Type")
puts "Body:\n" + response.body

The status code can be used to check whether the request was successfully processed or not: codes 2xx represent success, codes 3xx represent a redirection, codes 4xx represent client errors, codes 5xx represent server errors, and codes 10xx represent SFML specific errors which are not part of the HTTP standard.

Example: sending scores to an online server#

Here is a short example that demonstrates how to perform a simple task: Sending a score to an online database.

def send_score(score, name)
  # prepare the request
  request ="/send-score.html", SF::Http::Request::Post)

  # encode the parameters in the request body
  request.body = "name=" + name + "&score=" + score

  # send the request
  http ="")
  response = http.send_request(request)

  # check the status
  if response.status.ok?
    # check the contents of the response
    puts response.body
    puts "request failed"

Of course, this is a very simple way to handle online scores. There's no protection: Anybody could easily send a false score. A more robust approach would probably involve an extra parameter, like a hash code that ensures that the request was sent by the program. That is beyond the scope of this tutorial.

And finally, here is a very simple example of what the PHP page on server might look like.

$name = $_POST['name'];
$score = $_POST['score'];

if (write_to_database($name, $score)) { // this is not a PHP tutorial :)
    echo 'name and score added!';
} else {
    echo 'failed to write name and score to database...';