go-wol

Simple wake on LAN magic packet generator for golang

WOL in the world?

Wake-on-LAN (WOL) describes a simple data link layer protocol which tells a listening ethernet interface to power the target machine up.

Each target system typically exposes a setting in it's BIOS which enables or disables the system's WOL capabilities (since this can slowly consume a small amount of standby power).

If you are looking for a tepid overview of the core components of this project in the form of a blog post: see here

Magic Packets (of what?)

The listening interface just looks for a Magic Packet with it's MAC address encoded in the WOL scheme. The packet is basically 6 bytes of 0xFF followed by 16 repetitions of the destination interface's MAC address (102 bytes total). The Magic Packet does not have to be exactly 102 bytes, but it's relevant payload is. This payload can be sandwiched anywhere in the broadcast's payload.

It is important to remember that since this is typically sent over the data link layer, the target machine's IP address is irrelevant.

Installation

$go get github.com/sabhiram/go-wol
$wol wake 08:BA:AD:F0:00:0D

Usage

Valid commands include:

    {`wake`,   `wakes up a machine by mac address or alias`},
    {`list`,   `lists all mac addresses and their aliases`},
    {`alias`,  `stores an alias to a mac address`},
    {`remove`, `removes an alias or a mac address`},

With the following options (mostly apply to the wake command):

    {`v`, `version`,   `prints the application version`},
    {`h`, `help`,      `prints the help menu`},
    {`p`, `port`,      `udp port to send bcast packet to`},
    {`b`, `bcast`,     `broadcast IP to send packet to`},
    {`i`, `interface`, `outbound interface to broadcast using`},

Wake up a machine with mac address 00:11:22:aa:bb:cc:

wol wake 00:11:22:aa:bb:cc

Store an alias:

wol alias skynet 00:11:22:aa:bb:cc

Note that when waking up a machine, the wake command pretty much exists for clarity. You can safely omit it (unless your alias name is list, wake, alias or remove).

Wake up a machine using an alias:

wol wake skynet
wol skynet

View all aliases and corresponding MAC addresses:

wol list

Delete an alias:

wol remove skynet

Store an alias to a MAC using a default interface:

wol alias skynet 00:11:22:aa:bb:cc eth0

Specify a Broadcast Interface (Local to the sender):

wol wake skynet -i eth0

# or

wol wake skynet --interface eth0

Please note that when specifying an interface to use, you can set that as part of the alias. However, if the -i option is specified, the specified interface will be used and the one in the alias map will be ignored.

Specify the Broadcast Port and IP:

wol wake 00:11:22:aa:bb:cc -b 255.255.255.255 -p 7

# or

wol wake skynet --bcast 255.255.255.255 --port 7

Defaults

The default Broadcast IP is 255.255.255.255 and the UDP Port is 9. Typically the UDP port is either 7 or 9. The default interface is set to "" which tell the program to use any available interface.

Alias file

The alias file is typically stored in the user's Home directory under the path of ~/.config/go-wol/aliases. This is a very simple BoltDB which reads a per-alias Gob made up of a MAC address and an optional preferred outbound interface.

This is how wol expects MAC addresses to look

The following MAC addresses are valid and will match: 01-23-45-56-67-89, 89:0A:CD:EF:00:12, 89:0a:cd:ef:00:12

The following MAC addresses are not (yet) valid: 1-2-3-4-5-6, 01 23 45 56 67 89

Tests

All commits and PRs will get run on TravisCI and have corresponding coverage reports sent to Coveralls.io.

To run the tests:

go test -v github.com/sabhiram/go-wol/...

Contributors:

Thanks to:

1. @traetox for helping adding the optional outbound interface for MagicPackets, and swapping out the Gob written to disk for a more elegant BoltDB solution.