5.1. Modem type commands

This chapter describes commands that are specific to modem type links. These commands apply to the currently active link, and are only valid if the currently active link has type modem.

set modem device devname

Modem links operate over serial ports. This command tells mpd which serial port to use for this link, and is required. The devname should be the pathname of a serial device, e.g., /dev/cuad0.

set modem var $variable string

Pre-sets the chat script variable $variable to contain the string string. See the chapter on chat scripting for more information on chat variables.

set modem speed speed

This commands sets the initial serial port speed when opening the serial device, e.g., 9600, 57600, 115200. Note that you can always change the serial port speed later from within the chat script.

set modem script connect-script

This command tells mpd which chat script to run in order to initiate a PPP connection for this link. The connect-script should correspond to a label in mpd.script. Mpd will jump to this label after opening the serial port device. If connect-script is not set, then the chat phase of the connection is skipped (e.g., if you have a direct null modem connection).

set modem idle-script idle-script

This command tells mpd what to do with the serial port when the link is not connected. If no idle-script is set, then mpd will leave the serial port closed when not connected. Otherwise, when the link is disconnected mpd runs the idle-script chat script. If this script returns failure, then mpd restarts the script.

Otherwise, (i.e., if it returns success) mpd examines the contents of the $IdleResult chat variable to decide what to do next. If it equals answer then mpd will assume that an incoming call has been answered and immediately enter PPP negotiation. If it equals ringback then mpd will close the serial port, reopen it, and initiate an outgoing connection normally (i.e., using connect-script).

If $IdleResult contains anything else or is not set, then mpd acts as if failure had occurred and simply restarts the script.

set modem watch +/-signal ...

Mpd normally tracks the carrier detect signal on the serial port and drops the connection when this signal is lost. You can disable this behavior with set modem watch -cd. Also, mpd can do the same thing with the DSR signal, though the default is to ignore DSR. To enable watching of the DSR signal, use set modem watch +dsr.