At first, you can get a list of network interfaces on your computer via getSupportedInterfaces(). It returns an array of strings that are the names of the network interfaces, e.g. "eth1" or "wlan0".

The full information about the state of a network interface can be retrieved with getCurrentConfig(). It returns a Net_Wifi_Config object. To just check if an interface is connected, use the isConnected() method also takes the interface name as only parameter.

A Net_Wifi_Config looks like this:

Net_Wifi_Config {
  activated     => bool(true)
  associated    => bool(true)
  ap            => string(17) "00:03:C9:44:34:2C"
  ssid          => string(4) "free"
  mode          => string(7) "managed"
  nick          => NULL
  rate          => string(2) "54"
  power         => string(2) "20"
  protocol      => string(12) "IEEE 802.11g"
  rssi          => string(3) "-37"
}