diff --git a/Cargo.lock b/Cargo.lock
index 9df2a7a..9eb98ec 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -135,6 +135,12 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
 
+[[package]]
+name = "bitflags"
+version = "1.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
+
 [[package]]
 name = "blocking"
 version = "1.2.0"
@@ -155,6 +161,12 @@ version = "3.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c1ad822118d20d2c234f427000d5acc36eabe1e29a348c89b63dd60b13f28e5d"
 
+[[package]]
+name = "bytes"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec8a7b6a70fde80372154c65702f00a0f56f3e1c36abbc6c440484be248856db"
+
 [[package]]
 name = "cache-padded"
 version = "1.2.0"
@@ -265,6 +277,15 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "hermit-abi"
+version = "0.1.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62b467343b94ba476dcb2500d242dadbb39557df889310ac77c5d99100aaac33"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "instant"
 version = "0.1.12"
@@ -310,6 +331,16 @@ version = "0.2.132"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8371e4e5341c3a96db127eb2465ac681ced4c433e01dd0e938adbef26ba93ba5"
 
+[[package]]
+name = "lock_api"
+version = "0.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9f80bf5aacaf25cbfc8210d1cfb718f2bf3b11c4c54e5afe36c236853a8ec390"
+dependencies = [
+ "autocfg",
+ "scopeguard",
+]
+
 [[package]]
 name = "log"
 version = "0.4.17"
@@ -326,6 +357,28 @@ version = "2.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
 
+[[package]]
+name = "mio"
+version = "0.8.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "57ee1c23c7c63b0c9250c339ffdc69255f110b298b901b9f6c82547b7b87caaf"
+dependencies = [
+ "libc",
+ "log",
+ "wasi",
+ "windows-sys",
+]
+
+[[package]]
+name = "num_cpus"
+version = "1.13.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "19e64526ebdee182341572e50e9ad03965aa510cd94427a4549448f285e957a1"
+dependencies = [
+ "hermit-abi",
+ "libc",
+]
+
 [[package]]
 name = "once_cell"
 version = "1.14.0"
@@ -338,6 +391,29 @@ version = "2.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "427c3892f9e783d91cc128285287e70a59e206ca452770ece88a76f7a3eddd72"
 
+[[package]]
+name = "parking_lot"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3742b2c103b9f06bc9fff0a37ff4912935851bee6d36f3c02bcc755bcfec228f"
+dependencies = [
+ "lock_api",
+ "parking_lot_core",
+]
+
+[[package]]
+name = "parking_lot_core"
+version = "0.9.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "09a279cbf25cb0757810394fbc1e359949b59e348145c643a939a525692e6929"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "redox_syscall",
+ "smallvec",
+ "windows-sys",
+]
+
 [[package]]
 name = "pin-project-lite"
 version = "0.2.9"
@@ -382,6 +458,15 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "redox_syscall"
+version = "0.2.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fb5a58c1855b4b6819d59012155603f0b22ad30cad752600aadfcb695265519a"
+dependencies = [
+ "bitflags",
+]
+
 [[package]]
 name = "regex"
 version = "1.6.0"
@@ -399,6 +484,21 @@ version = "0.6.27"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a3f87b73ce11b1619a3c6332f45341e0047173771e8b8b73f87bfeefb7b56244"
 
+[[package]]
+name = "scopeguard"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
+
+[[package]]
+name = "signal-hook-registry"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e51e73328dc4ac0c7ccbda3a494dfa03df1de2f46018127f60c693f2648455b0"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "simple-auth"
 version = "0.1.0"
@@ -407,6 +507,7 @@ dependencies = [
  "json",
  "lazy_static",
  "regex",
+ "tokio",
 ]
 
 [[package]]
@@ -418,6 +519,12 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "smallvec"
+version = "1.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2fd0db749597d91ff862fd1d55ea87f7855a744a8425a64695b6fca237d1dad1"
+
 [[package]]
 name = "socket2"
 version = "0.4.7"
@@ -439,6 +546,38 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "tokio"
+version = "1.21.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0020c875007ad96677dcc890298f4b942882c5d4eb7cc8f439fc3bf813dc9c95"
+dependencies = [
+ "autocfg",
+ "bytes",
+ "libc",
+ "memchr",
+ "mio",
+ "num_cpus",
+ "once_cell",
+ "parking_lot",
+ "pin-project-lite",
+ "signal-hook-registry",
+ "socket2",
+ "tokio-macros",
+ "winapi",
+]
+
+[[package]]
+name = "tokio-macros"
+version = "1.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9724f9a975fb987ef7a3cd9be0350edcbe130698af5b8f7a631e23d42d052484"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "unicode-ident"
 version = "1.0.3"
@@ -467,6 +606,12 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9d5b2c62b4012a3e1eca5a7e077d13b3bf498c4073e33ccd58626607748ceeca"
 
+[[package]]
+name = "wasi"
+version = "0.11.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
+
 [[package]]
 name = "wasm-bindgen"
 version = "0.2.82"
@@ -573,3 +718,46 @@ name = "winapi-x86_64-pc-windows-gnu"
 version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
+
+[[package]]
+name = "windows-sys"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea04155a16a59f9eab786fe12a4a450e75cdb175f9e0d80da1e17db09f55b8d2"
+dependencies = [
+ "windows_aarch64_msvc",
+ "windows_i686_gnu",
+ "windows_i686_msvc",
+ "windows_x86_64_gnu",
+ "windows_x86_64_msvc",
+]
+
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9bb8c3fd39ade2d67e9874ac4f3db21f0d710bee00fe7cab16949ec184eeaa47"
+
+[[package]]
+name = "windows_i686_gnu"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "180e6ccf01daf4c426b846dfc66db1fc518f074baa793aa7d9b9aaeffad6a3b6"
+
+[[package]]
+name = "windows_i686_msvc"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2e7917148b2812d1eeafaeb22a97e4813dfa60a3f8f78ebe204bcc88f12f024"
+
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4dcd171b8776c41b97521e5da127a2d86ad280114807d0b2ab1e462bc764d9e1"
+
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.36.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c811ca4a8c853ef420abd8592ba53ddbbac90410fab6903b3e79972a631f7680"
diff --git a/Cargo.toml b/Cargo.toml
index 20e5bef..841e835 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,6 +9,7 @@ edition = "2021"
 json = "0.12.4"
 lazy_static = "1.4.0"
 regex = "1"
+tokio = { version = "1.21.1", features = ["full"] }
 
 [dependencies.async-std]
 version = "1.6"
diff --git a/src/main.rs b/src/main.rs
index fb4b02a..f8dd27c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,45 +1,38 @@
 mod handlers;
 
 use std::io::prelude::*;
-use std::net::TcpListener;
-use std::net::TcpStream;
+
+use tokio::{
+    io::{AsyncReadExt, AsyncWriteExt},
+    net::{TcpListener, TcpStream},
+};
 
 use handlers::handle_request;
 
-// TODO: must be set in a conf file
 const SERVER_URL: &str = "127.0.0.1:9000";
 
-// switch to an asynchronous main function
-#[async_std::main]
+#[tokio::main]
 async fn main() {
-    let listener = TcpListener::bind(SERVER_URL).unwrap();
-    println!("server is listening at {}", SERVER_URL);
-    for stream in listener.incoming() {
-        let stream = stream.unwrap();
+    let listener = TcpListener::bind(SERVER_URL).await.unwrap();
+
+    loop {
+        let (stream, _) = listener.accept().await.unwrap();
         handle_connection(stream).await;
     }
 }
 
 async fn handle_connection(mut stream: TcpStream) {
-    let mut buffer = [0; 1024];
-    stream.read(&mut buffer).unwrap();
+    let mut buffer: [u8; 1024] = [0; 1024];
+    let n = stream.read(&mut buffer).await.unwrap();
 
-    // transform buffer bytes array into `String`
-    let buffer_string = String::from_utf8_lossy(&buffer);
-    let request = handle_request(&buffer_string);
+    println!("buffer : {:?}", std::str::from_utf8(&buffer[0..n]));
 
-    // TODO: `Response` struct must be implemented
-    let status_line = if request.start_line.target == "/".to_string() {
-        "HTTP/1.1 200 OK\r\n"
-    } else {
-        "HTTP/1.1 404 NOT FOUND\r\n"
-    };
-
-    let content_type = "Content-Type: application/json\r\n\r\n";
-    let json = r#"{"access_token":"AAAAAAAAAAAA.BBBBBBBBBB.CCCCCCCCCC","refresh_token": "DDDDDDDDDDD.EEEEEEEEEEE.FFFFF"}"#;
-    let response = format!("{status_line}{content_type}{json}\n");
-
-    println!("return status code : {}", status_line);
-    stream.write(response.as_bytes()).unwrap();
-    stream.flush().unwrap();
+    let contents = "{\"balance\": 0.00}";
+    let response = format!(
+        "HTTP/1.1 200 OK\r\nContent-Type: application/json\r\nContent-Length: {}\r\n\r\n{}",
+        contents.len(),
+        contents
+    );
+    stream.write(response.as_bytes()).await.unwrap();
+    stream.flush().await.unwrap();
 }