08 March, 2008

Wake On LAN with Ericsson W25

After a lot of unsuccessfull experiments, finally I could manage to send out a Wake On LAN magic packet from the W25. The solution is not universal, because I rely on a second router on my home network, to respond to an outgoing TCP packet.

The difficulty in WOL for the W25 is that I found only the netcat (nc) program suitable for sending out IP packets from the router and the version of nc implemented in the W25 doesn't support UDP packets.

I have manually constructed a magic packet and saved it to a file. The command:

nc router2 80 < wakecode.bin

sends this packet the the second routers which silenlty ignores it, because this is not a valid HTTP request. But there is still a problem, that in a swicthed LAN this traffic reaches only the second router and not the computer to be waked up. The solution for this is to play with the arp addresses and manually assign the broadcast ethernet addres to the second routers IP address:

arp -s ff:ff:ff:ff:ff:ff

after waking up the computer you can delete this assignment with the following command:

arp -d

Implementig the same without using a second router or computer on the internal newtork is challanging, because you have to send out packet to the network, which has to be responded by the same machine. May be there is a solution by tweaking in iptables, or may be there is a command that you can use send out udp packages, but I have not found it.

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