add HTTP Updater docu

doc/ota_updates.md

@@ -3,21 +3,20 @@ title: OTA Update
 ---
 
 ## Table of Contents
- * [Requirements](#Requirements)
+ * [Basic Requirements](#basic-requirements)
  * [Arduino IDE](#arduino-ide)
  * [HTTP Server](#http-server)
  * [Stream Interface](#stream-interface)
  
-## Requirements
+## Basic Requirements
 
-Basic requirement:
 - Flash chip size is 2x the size of the sketch
  
 ## Arduino IDE
 
 TODO describe Arduino IDE OTA process
 
-### Requirements
+#### Requirements
  - The ESP and the Computer must be connected to the Same network.
 
 
@@ -27,18 +26,29 @@ the ```ESPhttpUpdate``` class can check for updates and download a binary file f
 It is possible to download updates from every IP or domain address on the Network or Internet.
 
 
-### Requirements
+#### Requirements
  - web server
 
 
-### Arduino code
+#### Arduino code
+
+##### simple updater
+
+the Simple Updater downloads the File every time the function is called.
 
-simple updater:
 ```cpp
 ESPhttpUpdate.update("192.168.0.2", 80, "/arduino.bin");
 ```
 
-advanced:
+##### advanced updater
+
+Its possible to point to a script at the server.
+If a version String is delivered to the Function this String will be send to the server.
+A Server side Update check is now possible.
+
+the Server can return a binary file for update (Header 200)
+or it return header 304 to notify the ESP that no Update is needed.
+
 ```cpp
 t_httpUpdate_return ret = ESPhttpUpdate.update("192.168.0.2", 80, "/esp/update/arduino.php", "optional current version string here");
 switch(ret) {
@@ -54,9 +64,93 @@ switch(ret) {
 }
 ```
 
-### Server request handling
+#### Server request handling
+
+##### simple updater
+
+for the simple Updater the Server only needs to deliver the binary file for update.
+
+##### advanced updater
+
+for advanced update management a Script needs to run at the Server side, for example a PHP script.
+at every Update request the the ESP sends some informations in the Header to the Server
+
+example Header data:
+```
+	[HTTP_USER_AGENT] => ESP8266-http-Update
+    [HTTP_X_ESP8266_STA_MAC] => 18:FE:AA:AA:AA:AA
+    [HTTP_X_ESP8266_AP_MAC] => 1A:FE:AA:AA:AA:AA
+    [HTTP_X_ESP8266_FREE_SPACE] => 671744
+    [HTTP_X_ESP8266_SKETCH_SIZE] => 373940
+    [HTTP_X_ESP8266_CHIP_SIZE] => 524288
+    [HTTP_X_ESP8266_SDK_VERSION] => 1.3.0
+    [HTTP_X_ESP8266_VERSION] => DOOR-7-g14f53a19
+```
+
+with this information the script now can check if a update is needed.
+It is also possible to deliver different binary´s based on the MAC address for example.
+
+script example:
+```php
+<?PHP
+
+header('Content-type: text/plain; charset=utf8', true);
+
+function check_header($name, $value = false) {
+	if(!isset($_SERVER[$name])) {
+		return false;
+	}
+	if($value && $_SERVER[$name] != $value) {
+		return false;
+	}
+	return true;
+}
+
+function sendFile($path) {
+	header($_SERVER["SERVER_PROTOCOL"].' 200 OK', true, 200);
+	header('Content-Type: application/octet-stream', true);
+	header('Content-Disposition: attachment; filename='.basename($path));
+	header('Content-Length: '.filesize($path), true);
+	readfile($path);
+}
+
+if(!check_header('HTTP_USER_AGENT', 'ESP8266-http-Update')) {
+	header($_SERVER["SERVER_PROTOCOL"].' 403 Forbidden', true, 403);
+	echo "only for ESP8266 updater!\n";
+	exit();
+} 
+
+if(
+	!check_header('HTTP_X_ESP8266_STA_MAC') || 
+	!check_header('HTTP_X_ESP8266_AP_MAC') ||
+	!check_header('HTTP_X_ESP8266_FREE_SPACE') ||
+	!check_header('HTTP_X_ESP8266_SKETCH_SIZE') ||
+	!check_header('HTTP_X_ESP8266_CHIP_SIZE') ||
+	!check_header('HTTP_X_ESP8266_SDK_VERSION') ||
+	!check_header('HTTP_X_ESP8266_VERSION')
+) {
+	header($_SERVER["SERVER_PROTOCOL"].' 403 Forbidden', true, 403);
+	echo "only for ESP8266 updater! (header)\n";
+	exit();
+}
+
+$db = array(
+	"18:FE:AA:AA:AA:AA" => "DOOR-7-g14f53a19",
+	"18:FE:AA:AA:AA:BB" => "TEMP-1.0.0"
+);
+
+if(isset($db[$_SERVER['HTTP_X_ESP8266_STA_MAC']])) {
+	if($db[$_SERVER['HTTP_X_ESP8266_STA_MAC']] != $_SERVER['HTTP_X_ESP8266_VERSION']) ) {
+		sendFile("./bin/".$db[$_SERVER['HTTP_X_ESP8266_STA_MAC']]."bin");
+	} else {
+		header($_SERVER["SERVER_PROTOCOL"].' 304 Not Modified', true, 304);
+	}
+}
+
+header($_SERVER["SERVER_PROTOCOL"].' 500 no version for ESP MAC', true, 500);
+
+```
 
-TODO server side 
 
 ## Stream Interface