curl --request POST \
  --url https://api.demo.fuelboss.net/oauth/token \
  --header 'Content-Type: application/x-www-form-urlencoded' \
  --data 'grant_type=<string>' \
  --data 'client_id=<string>' \
  --data 'client_secret=<string>'

import requests

url = "https://api.demo.fuelboss.net/oauth/token"

payload = {
    "grant_type": "<string>",
    "client_id": "<string>",
    "client_secret": "<string>"
}
headers = {"Content-Type": "application/x-www-form-urlencoded"}

response = requests.post(url, data=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {'Content-Type': 'application/x-www-form-urlencoded'},
  body: new URLSearchParams({grant_type: '<string>', client_id: '<string>', client_secret: '<string>'})
};

fetch('https://api.demo.fuelboss.net/oauth/token', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.demo.fuelboss.net/oauth/token",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => "grant_type=%3Cstring%3E&client_id=%3Cstring%3E&client_secret=%3Cstring%3E",
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/x-www-form-urlencoded"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.demo.fuelboss.net/oauth/token"

	payload := strings.NewReader("grant_type=%3Cstring%3E&client_id=%3Cstring%3E&client_secret=%3Cstring%3E")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Content-Type", "application/x-www-form-urlencoded")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.demo.fuelboss.net/oauth/token")
  .header("Content-Type", "application/x-www-form-urlencoded")
  .body("grant_type=%3Cstring%3E&client_id=%3Cstring%3E&client_secret=%3Cstring%3E")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.demo.fuelboss.net/oauth/token")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Content-Type"] = 'application/x-www-form-urlencoded'
request.body = "grant_type=%3Cstring%3E&client_id=%3Cstring%3E&client_secret=%3Cstring%3E"

response = http.request(request)
puts response.read_body

{
  "access_token": "<string>",
  "token_type": "<string>",
  "expires_in": 123
}

{
  "error": "<string>",
  "error_description": "<string>"
}