DD-wrt: control radio on a Cisco Linksys E2000

Some people prefer to have their wifi turned off at night. DD-wrt already provides out of the box reprogrammability of the WPS button so you can use that button to turn the wifi off/on.

If you want to use a cron job to automate this process, you need to know the command line. I tried using the wl command:

wl radio off

Unfortunately this doesn’t do much. We might need to specify the network interface on which to apply the command. List the network interfaces using the ip addr command:

root@DD-WRT:~# ip a
1: lo: <LOOPBACK,MULTICAST,UP,10000> mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet brd scope host lo
2: eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast
    link/ether c0:c1:c0:ab:6c:70 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc pfifo_fast
    link/ether c0:c1:c0:ab:6c:72 brd ff:ff:ff:ff:ff:ff
4: teql0:  mtu 1500 qdisc noop
5: tunl0:  mtu 1480 qdisc noop
    link/ipip brd
6: gre0:  mtu 1476 qdisc noop
    link/gre brd
7: vlan1@eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc noqueue
    link/ether c0:c1:c0:ab:6c:70 brd ff:ff:ff:ff:ff:ff
8: vlan2@eth0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc noqueue
    link/ether c0:c1:c0:ab:6c:71 brd ff:ff:ff:ff:ff:ff
    inet 178.117.xxx.xxx/20 brd 178.117.xxx.255 scope global vlan2
9: br0: <BROADCAST,MULTICAST,PROMISC,UP,10000> mtu 1500 qdisc noqueue
    link/ether c0:c1:c0:ab:6c:70 brd ff:ff:ff:ff:ff:ff
    inet brd scope global br0
    inet brd scope global br0:0
10: etherip0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop
    link/ether f6:1f:60:c5:50:bf brd ff:ff:ff:ff:ff:ff

I’m no network expert so I checked the MAC address of the wifi interface in the web admin Status > Wireless page ( ) and figured eth1 must be the wifi interface.
And indeed, using the following command it worked!

wl -i eth1 radio off

You can check whether radio state changes in the wireless status page mentioned above. For automation, put these commands in a cron job on the Administration > Management page ( ).

Java mail and SMTP: “501 HELO requires valid address”

I was trying to send a mail through Java the other day and kept stumbling upon the following exception:

javax.mail.MessagingException: 501 HELO requires valid address

I thought it was caused by an authentication problem or my provider preventing me from sending from a random address.
The former I tried to address by making sure I was fully authenticated as to prove I was not trying to send spam. In java mail the following properties are relevant for sending authenticated mail using TLS:

-Dmail.smtp.host=<your smtp server>
-Dmail.smtp.username=<your username>
-Dmail.smtp.password=<your password>

and setting an authenticator on the mail session object:

Session session = Session.getDefaultInstance(System.getProperties(), new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication(MAIL_USER, MAIL_PWD);

The latter I tried to address by sending from an alias that was associated with the original mailbox (user/pwd combo). Yet I kept getting the same exception.

Looking up the SMTP protocol and testing with telnet, I found out that normally you are supposed to provide a domain name when issueing the EHLO or HELO command. Since the api does not provide any methods for that, I looked for some more properties and indeed, it turns out you need to set


to make it provide the hostname for the EHLO command. According to the docs:
Should not normally need to be set if your JDK and your name service are configured properly.” but apparently my case was not normal ­čÖé

Also worth noting is that you can turn on debug output with: