PPP device driver

The PPP device driver uses a couple of environment variables. These are

• PPP.PORT. Communication port number
• PPP.IRQ. Communication port IRQ number
• PPP.BAUDRATE. Communication port baudrate
• PPP.DIAL. Dial hayes command (i.e. atd01234)
• PPP.USERNAME. Username for authentication
• PPP.PASSWORD. Password for authentication
  

To do the dial-up you call OpenInternet, and to hangup you call CloseInternet. These two uses a counter, so if you call OpenInternet twice and CloseInternet once, you're still connected.