LogMeIn is a useful remote control service: shame it doesn’t work when my home Mac has gone into power-saving sleep. I use an ADSL modem in bridge mode which provides a fixed public IP address to my Apple Time Capsule, which performs NAT and DCHP on my LAN. A Synology NAS and iMac are both connected to this /24 (in my case 192.168.1.* range) LAN via Ethernet. Both devices support wake-on-LAN (WoL), although the Synology server is always-on. So could I make use of the NAS to ‘wake up’ my sleeping iMac from a remote location, given that WoL does not work over the Internet?
There’s no reason this won’t work on another brand of NAS or with a PC.
The goods: a PHP script for WoL
I used the script here as a basis (the original source of which is not acknowledged), then simply iOS-ified it using the iWebKit framework to build a web app that can be saved to your iPhone Home screen.
- Download and copy the iWebKit framework folders (css, javascript, images) into your root web directory
- Create a new directory in your web root called ‘wol’ to contain the script and related files
- Create an Apple touch icon to place in the ‘wol’ folder (I named mine imac.png)
![iMac]( "imac.png")
- Create the following file in a text editor and save as index.php in the ‘wol’ folder
- Change the
<option value='xx:xx:xx:xx:xx:xx'>iMac</option>segments to the MAC address of the network card in the Mac you want to wake, plus to the name of the machine for identification purposes in the drop-down menu
<!DOCTYPE html>
<html lang="en">
<head>
<meta content="yes" name="apple-mobile-web-app-capable" />
<meta content="text/html; charset=utf-8" http-equiv="Content-Type" />
<meta content="minimum-scale=1.0, width=device-width, maximum-scale=0.6667, user-scalable=no" name="viewport" />
<link href="../css/style.css" rel="stylesheet" media="screen" type="text/css" />
<link href="../css/mozillaStyle.css" rel="stylesheet" media="screen" type="text/css" />
<link rel="icon" type="image/png" href="http://yourdomain.com/favicon.png" />
<link rel="apple-touch-icon" href="http://yourdomain.com/wol/imac.png" />
<script src="../javascript/functions.js" type="text/javascript"></script>
<title>Wake my Mac</title>
</head>
<body>
<div id="topbar">
<div id="title">Wake my Mac</div>
</div>
<div id="content">
<?php
flush();
$port = 9;
echo "<form name='WakeOnLan' method='GET' action='index.php'><fieldset>
<ul class='pageitem'>
<li class='textbox'>
<span class='header'>Select a Mac to wake</span> Tap drop-down menu, then tap switch
</li>
<li class='select'>
<select name='wake_machine' id='WakeOnLan'>
<option value='xx:xx:xx:xx:xx:xx'>iMac</option>
<option value='xx:xx:xx:xx:xx:xx'>MacBook</option>
</select>
<span class='arrow'></span>
</li>
<li class='checkbox'>
<span class='check'>
<span class='name'>Turn me</span>
<input onclick='submitform();' name='remember' type='checkbox' value='Wake' />
</span>
</li>
</ul>
</fieldset></form>
<script type='text/javascript'>
function submitform()
{
document.WakeOnLan.submit();
}
</script>";
function WakeOnLan($addr, $mac, $socket_number)
{
$addr_byte = explode(':', $mac);
$hw_addr = '';
for($a=0; $a <6; $a++)
$hw_addr .= chr(hexdec($addr_byte[$a]));
$msg = chr(255).chr(255).chr(255).chr(255).chr(255).chr(255);
for($a = 1; $a <= 16; $a++)
$msg .= $hw_addr;
$s = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP);
echo "<ul class='pageitem'>
<li class='textbox'><span class='header' style='color: #ccc;'>Result of WoL request</span>";
if($s == false)
{
echo "Could not create socket<br />n";
echo "Error: '".socket_last_error($s)."' - " . socket_strerror(socket_last_error($s));
return FALSE;
}
else
{
$opt_ret = socket_set_option($s, 1, 6, TRUE);
if($opt_ret < 0)
{
echo "setsockopt() failed, error: " . strerror($opt_ret) . "<br />n";
return FALSE;
}
if(socket_sendto($s, $msg, strlen($msg), 0, $addr, $socket_number))
{
$content = bin2hex($msg);
echo "Data: <textarea readonly rows='1' name='content' cols=''.strlen($content).''>'.$content.'</textarea><br />n";
echo "Port: ".$socket_number."<br />n";
echo "MAC: ".$_GET['wake_machine']."<br />n";
socket_close($s);
return TRUE;
}
else
{
echo "Magic packet could not be sent<br />";
return FALSE;
}
}
}
$result = null;
if($_GET["wake_machine"] != "")
$result = WakeOnLan("192.168.1.255", $_GET["wake_machine"], $port);
if($result != null)
echo "<hr><img src='http://yourdomain.com/wol/imac.png' height='64' width='64' /><br />WoL for ".$_GET["wake_machine"]." successful<br />n";
echo "</li></ul>";
?>
</div>
<div id="footer">
<a class="noeffect" href="http://www.synology.com/">Synology</a> • <a class="noeffect" href="http://snippetspace.com/projects/iwebkit/">iWebKit</a>
</div>
</body>
</html>This works for me when initiated from my LAN and from the Internet (e.g. via a mobile network), but only if the Mac is powered on and sleeping. It does not turn on a Mac that has been fully shut down.
The results: a WoL web app
Save to the iOS Home screen
Main interface on loading the web app
Choosing a Mac to wake-on-LAN
Results of the wake request
Research notes
- The ‘broadcast address’ is an IP address (192.168.1.255), not assigned to a physical device, but reserved for WoL
- The WoL signal can be sent only over a wired LAN (i.e. Ethernet), so will not reach a device on your LAN that is connected via WiFi
- Because both the NAS sending the signal and the computer to be woken are on the same LAN, it should not be necessary to create a port forwarding rule on the Time Capsule to target the iMac (i.e. the public IP address does not need to forward to the private (LAN) IP address of the ‘listening’ iMac or send a ‘magic packet’ to that device on UDP port 9)
- Furthermore, Time Capsule (as with many routers apparently) will not allow a port forwarding rule to be created for the broadcast IP address (the Save button is disabled)
![AirPort Utility]( "AirPort Utility.jpg")
- It is possible to export the Time Capsule configuration, edit it, then reimport—but the Time Capsule will take no notice
- It is apparently possible to change your LAN subnet mask to 255.255.255.128 and use a broadcast IP of 192.168.0.127 to overcome this limitation; this is because WoL requires both the device issuing the magic packet and the device receiving it to be on the same subnet
- Apple’s Wake on Demand/ Back to My Mac facilities aren’t much use unless you have a mobile Mac to remote in with to reach another Mac at home: this doesn’t work from an iOS device
- As well as testing with LogMeIn, I tested with Parallels Desktop and the above script (once the iMac is online) allows Parallels to connect and provide remote access to OS X (it doesn’t work only with virtual machines)
