Previous INDEX Next
Dealing with Unicode in filenames Crimson Motherboard Death

Getting Wake On Lan (WOL) working

Some time ago, I'd experimented with Wake On Lan (WOL) using amber, the most modern PC in the house, as the target. I'd tried a couple of ways; using a python program I'd found in the internet and also the FreeBSD wol port. However, I simply could not get it to work.

The BIOS seemed to be setup correctly. The power supply was quite old, and maybe not up to the WOL specs, so I replaced that. No difference. May be the router I was using (Netgear DG834N) was doing something? I tried a direct connection (using a cross-wired lan cable); still no joy. In the end I gave up trying; more important things to do.

Later, the Netgear router started having wireless problems. It was out of warranty, so time for a replacement, as the backup router from BeThere (the BeBox is a Thompson 585v7) was subject to intermittent cut outs (probably due to overheating, as placing it upside down reduced the incidence).

After a bit of research, I bought a Draytek 2820n. I'd had a Draytek before ((the 2800) which I had replaced as its ability to handle the ADSL2+ line provided by BeThere was non-existent. Reports from existing BeThere users showed that the 2820n, however, worked fine.

While browsing the router's capabilities, I noticed it provided a WOL function. Hmm, would it work? Well, yes it did! Fantastic, so I tried from the FreeBSD server using the wol program. Still didn't work. What was going on?

Maybe wol was broken somehow. Did wake.py do any better?

  [mark@topaz:~] python ~/dev/python/wake.py  00:21:85:5E:A9:D9
  sending magic packet to 255.255.255.255:9 with 00:21:85:5E:A9:D9
  [mark@topaz:~]%  

No, it didn't. However, seeing the above message from wake.py, combined with re-reading the command arguments supported by wol gave me an idea. Here's the key argument description from wol:

  -h HOST
  --host=HOST
  -i HOST
  --ipaddr=HOST
      Broadcast packet to this IP address or hostname. This is important
      if your wol client is a multihomed host and you want to send only
      to one subnet (default IP address is 255.255.255.255).

Maybe I should be sending the packet to the local subnet, i.e. 192.168.0.255, rather than the entire world? So I tried this:

  wol -i 192.168.0.255 00:21:85:5E:A9:D9

Success! amber awakes and Corwin will walk the pattern once more...

I'm not sure why this works; maybe the router firewall quenches global broadcasts to 255.255.255.255? Although that doesn't explain why it didn't work with a direct cross-over cable connection; maybe I should test that again when I have time.

Previous INDEX Next
Dealing with Unicode in filenames Crimson Motherboard Death