Wake-on-LAN
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Wake on LAN (WOL, sometimes WoL) is an Ethernet computer networking standard that allows a computer to be turned on or woken up remotely by a network message.
Technical details
System requirements - IBM PC Compatible
Wake on LAN (WoL) support is implemented in the motherboard of the computer. Most modern motherboards with an embedded Ethernet controller support WoL without the need for an external cable. Older motherboards must have a WAKEUP-LINK header onboard and connected to the network card via a special 3-pin cable; however, systems supporting the PCI 2.2 standard coupled with a PCI 2.2 compliant network adapter typically do not require a WoL cable as the required standby power is relayed through the PCI bus.
Wake on LAN must be enabled in the Power Management section of the motherboard's BIOS. It may also be necessary to configure the computer to reserve power for the network card when the system is shut down.
In addition, in order to get WoL to work it is sometimes required to enable this feature on the card. This can be done in Windows from the properties of the network card in the device manager, on the "Power Management" tab. Check "Allow this device to bring the computer out of standby" and then "Only allow management stations to bring the computer out of standby" to make sure it does not wake up on every single network activity that occurs. For Linux, there is a FAQ available concerning this issue.
How it works
Wake-on-LAN is not restricted to LAN (Local area network) traffic. It works with all network traffic, including Internet traffic.
The general process of waking a computer up remotely over a network connection can be explained thus:
The target computer is shut down (Sleeping, Hibernating or Soft Off, i.e. ACPI state G1 or G2), with power reserved for the network card. The network card listens for a specific packet, called the "Magic Packet." The Magic Packet is broadcast on the broadcast address for that particular subnet (or an entire LAN, though this requires special hardware and/or configuration). When the listening computer receives this packet, it checks it for the correct information, and then switches on and boots if the Magic Packet is valid.
The magic packet is sent on the Data link or OSI-2 layer and broadcast to all NICs (within the network of the broadcast address). Therefore, it does not matter whether the remote host has a fixed or dynamic IP-address (OSI-3 layer).
In order for Wake on LAN to work, parts of the network interface need to stay on. This increases the standby power used by the computer. If Wake on LAN is not needed, turning it off may reduce power consumption while the computer is off but still plugged in.[1]
Magic Packet
The Magic Packet is a broadcast frame containing anywhere within its payload 6 bytes of ones FF FF FF FF FF FF followed by sixteen repetitions of the target computer's MAC address.
Since the Magic Packet is only scanned for the string above, and not actually parsed by a full protocol stack, it may be sent as a broadcast packet of any network- and transport-layer protocol. It is typically sent as a UDP datagram to port 0, 7 or 9, or, in former times, as an IPX packet.
Security
Magic packets are sent via the Data link or OSI-2 layer, which is not secure and can be used or abused by anyone on the same LAN.
Firewalls may prevent clients within the public WAN to access the broadcast address of the private LAN.
Certain NIC's support a security feature called "SecureOn". It allows users to store within the NIC a hexadecimal password of 6 bytes. Clients have to append/ postfix this password to the magic packet. The NIC's awakes the system, only if the MAC address and password are correct. This security measure significantly decreases the risk of successful brute force attacks: 2 values per bit ^ ((6 bytes for remote host's mac_address + 6 bytes for password) * 8 bit per byte). Still, only a few NIC's and router manufacturers seem to support such security features.
Wake-on-LAN programs
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There are a number of programs available that make use of Wake-on-LAN. Below is a partial list.
Scripts
- WOL Python – a Python script.
- Wakeonlan – a Perl script that sends magic packets.
- Wake-on-LAN Tutorial, with PHP script
- Wake-on-LAN PHP script
Internet-based
- Wake on LAN Mob. A free simple Java MIDlet by jambel.net. Tested on Nokia 6630, Nokia N95 8GB, HTC Touch, HTC TyTN II.
- Wake-On-LAN Online - A free Wake-On-LAN over Internet with scheduling option up to one month. Mobile version for PDA/Phones.
- Online Wake-On-WAN
- Wake On Lan over the Internet
- Remotewakeup.com
- DSLReports.com - Wake Me Up - A free WOL packet generator that does not require Java. The tool will also remember your targets if you are a registered member.
- java WOL – OS independent Java WOL utility which can be launched from browser.
- microWoW A MIDP 2.0 MIDlet to power on your computer remotely. Open source (LGPL).
- JWakeME A Java MIDlet based Wake on LAN utility. Requires a MIDP 1.0 compliant device.
Hardware-based
- HyperWRT - Firmware for Linksys wireless routers with WOL GUI.
- DD-WRT - Firmware for Linksys wireless routers with WOL GUI.
- Tomato - Firmware for Linksys wireless routers with WOL GUI.
Source code
Here you can find source code about WOL functionality for different languages and platforms
- WOL .net - A VB.NET class to wake a device on the network.
- Wake on LAN in C# - Sample code to do Wake on LAN using C#
Microsoft Windows
- wol - Wake On LAN client - A Windows command-line util for WOL.
- SolarWinds Wake-On-LAN - a full-featured tool to remotely power on network PCs, included in the free version of the SolarWinds network toolkit.
- WOL - Magic Packet Sender 2007 – A free Windows Wake-on-LAN application that can store multiple WOL profiles and send magic packets.
- WakeOnLan (AquilaTech) - A free Windows WakeOnLan program that is full featured. WakeUp, Shutdown, Ping, global shutdown all in one. Requires .NET runtime
- FUSION WakeUp on Lan - A free Windows application. Using FUSION WakeUp on Lan you can take advantage of turning on a remote PC through the net interface.
- Intellipool Network Monitor - Network and Server monitoring software that can start computers with WOL on a schedule.
- AMD PCnet Magic Packet Utility - WOL application by AMD. It has a simple interface and features group announcements and scheduling.
- Wake-on-LAN - Free commandline wake-on-lan for Windows. Can wakeup a computer from over the internet.
- WakeUp - Free commandline wake-on-lan application for Windows.
- PowerState - Free GUI wake-on-lan application for Windows that also includes Windows WMI shutdown. Build and save lists of PCs for repeated use.
- WakeOnLan (Dipisoft) - A French freeware for wakeup, ping, restart, shutdown, close/lock session or hibernate distant computers. Works now in both GUI and commandline modes, last version is multilingual. Does not require .NET runtime.
- WOL 1.0.3 - A freeware Wake-On-Lan tool for all Windows versions.
- RSHUT PRO - A shareware tool for Wake-On-Lan and remote shutdown for all Windows versions.
- WakeOnLAN Packet Sniffer - Free troubleshooting tool.
- PacketTrap pt360 Wake On LAN - A complete network management tool which includes Wake On LAN capability as part of the free version of the software.
- Depicus Wake On Lan Tools - Standard alone WOL tools including magic packet sender and monitor for various platforms, no installation required.
Mac OS X
- Apple Remote Desktop - Multifunction tool with WOL capabilities
- Wake550 - OS X adaptation of Wakeonlan script
- WakeOnLan - A free utility and a Dashboard widget
Linux
PalmOS
Microsoft Windows Mobile
- RB|WakeOnLan - A free utility for PocketPC and Smartphone devices
See also
Additional resources
- Troubleshooting Remote Wake-up Issues - Useful WOL troubleshooting information from Intel
- AMD's Magic Packet Technology white paper Publication# 20213
- Wake-on-LAN white paper by Philip Lieberman describes the IBM / Intel alliance that created Wake-on-LAN
- SmallNetBuilder Guide to Set up WOL
- Wake-on-LAN History and How To Guide
- Wake-on-LAN Description and How To Guide
- ^ http://www.lesswatts.org/tips/ethernet.php Less Watts: Ethernet Tips & Tricks