Difference between revisions of "WiFi"

Revision as of 19:10, 1 March 2011

Pre-requites

Note: To configure WiFi you need to install wireless tools first (done by default for APF27 / PPS / APF51) and of course to have a running WiFi interface like: the one on APW extension board or PPS devt board or a USB to WiFi adapter, with corresponding Linux drivers loaded.

Common operations

List network interfaces supporting WiFi

 # iwconfig
 lo        no wireless extensions.
 
 eth0      no wireless extensions.
 
 sit0      no wireless extensions.
 
 wmaster0  no wireless extensions.
 
 wlan0     IEEE 802.11bg  ESSID:""  
           Mode:Managed  Frequency:2.412 GHz  Access Point: Not-Associated   
           Tx-Power=0 dBm   
           Retry min limit:7   RTS thr:off   Fragment thr=2352 B   
           Encryption key:off
           Power Management:off
           Link Quality:0/100  Signal level:112/146  Noise level:0/0
           Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
           Tx excessive retries:0  Invalid misc:0   Missed beacon:0

Note: Here our WiFi network interface is called wlan0. Depending on the number of your network interfaces or their model, this name could change. For example if using the Libertas drivers, the interface will be called eth1 (if eth0 is already used). In that case replace wlan0 with your interface name.

Show all Access Points (AP) available for your APF (here with wlan0 interface)

# iwlist wlan0 scan

wlan0     Scan completed :
          Cell 01 - Address: XX:XX:XX:66:47:48
                    ESSID:"TOTO"
                    Mode:Master
                    Channel:1
                    Frequency:2.412 GHz (Channel 1)
                    Quality=88/100  Signal level:25/100
                    Encryption key:on
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
                              9 Mb/s; 12 Mb/s; 18 Mb/s; 24 Mb/s; 36 Mb/s
                              48 Mb/s; 54 Mb/s
                    Extra:tsf=00000009d398fec8
                    Extra: Last beacon: 1390ms ago
...

Connect to an unencrypted AP

# iwconfig wlan0 essid AP_NAME

• Check it:

# iwconfig wlan0

Get an IP address

# udhcpc -i wlan0

Encryption settings

When configuring WiFi cryptography, only WEP can be setup easily from a terminal with single commands. If you want to configure your interface for WPA/WPA2, install and configure wpa_supplicant.

WEP configuration

This example is given for a WiFi Access Point named armadeus, the encoding key used here is not recommended, of course ;) :

 # iwconfig wlan0 essid armadeus
 # iwconfig wlan0 key 12345678901234567890
 # ifconfig wlan0 up             (if interface is not already up)
 ADDRCONF(NETDEV_UP): wlan0: link is not ready
 # ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready

Now, the WiFi adapter is ready and attached :

 # iwconfig
 lo        no wireless extensions.
 
 eth0      no wireless extensions.
 
 sit0      no wireless extensions.
 
 wmaster0  no wireless extensions.
 
 wlan0     IEEE 802.11bg  ESSID:"armadeus"  
           Mode:Managed  Frequency:2.437 GHz  Access Point: 00:1B:2F:E7:E4:08   
           Bit Rate=2 Mb/s   Tx-Power=7 dBm   
           Retry min limit:7   RTS thr:off   Fragment thr=2352 B   
           Encryption key:XXXXXXXXXXXXXXXXXXXXXXXXXX   Security mode:restricted
           Power Management:off
           Link Quality:0/100  Signal level:73/146  Noise level:0/0
           Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
           Tx excessive retries:0  Invalid misc:0   Missed beacon:0
 

Accessing outside world

We can manually configure the network to access Internet via the WiFi interface instead of the Ethernet one:

 # ifconfig eth0 down
 # ifconfig wlan0 192.168.0.212
 # route add default gw 192.168.0.1 dev wlan0

And configure the nameserver in /etc/resolv.conf

 domain dev.null
 nameserver 192.168.0.207
 ~                   
 ~
 ~

If you have a DHCP server on your network, you can also use it and previous steps (route+resolv.conf) will be done automatically:

# udhcpc -i wlan0

We can now ping the best website in the world :

 # ping www.armadeus.org
 PING www.armadeus.org (213.186.33.5): 56 data bytes
 64 bytes from 213.186.33.5: seq=0 ttl=122 time=66.735 ms
 64 bytes from 213.186.33.5: seq=1 ttl=122 time=50.392 ms
 ^C
 --- www.armadeus.org ping statistics ---
 2 packets transmitted, 2 packets received, 0% packet loss
 round-trip min/avg/max = 50.392/58.563/66.735 ms

Surf on the net

To surf on the web, you can use (for example) links software :

 # links www.armadeus.org

It's an ASCII internet browser. For more informations about Links.

Links

• Wireless Tools installation
• USB to WiFi adapters tested with Armadeus boards
• Measure the bandwidth of your interface