Talking Serially: Modem Configuration in HP-UX

Device Files

HP-UX does not provide device special files for use with modems by default. To create them, first determine the hardware path, and port number for the modem port:

# ioscan -C tty -fn
Class     I  H/W Path  Driver      S/W State   H/W Type     Description
========================================================================
tty       0  2/0/4     asio0       CLAIMED     INTERFACE    Built-in RS-232C
                      /dev/diag/mux0  /dev/mux0       /dev/tty0p0   
tty       1  5/0/2     asio0       CLAIMED     INTERFACE    Built-in RS-232C
                      /dev/diag/mux1  /dev/mux1       /dev/tty1p0

The output shows two serial interfaces, HP-UX calls them card instances, one at hardware path 2/0/4, and one at hardware path 5/0/2. In this example, let's use the one at hardware path 2/0/4, which corresponds to the first serial port on the back of the machine. To create the the device special files for this port issue the following commands:

For a dial-out modem:

# /usr/sbin/mksf -d asio0 -H 2/0/4 -a1 -v
        making cul0p0 c 1 0x000001

For a dial-in modem:

# /usr/sbin/mksf -d asio0 -H 2/0/4 -a2 -v
        making ttyd0p0 c 1 0x000002

For a direct connection to the modem, which can be used for debugging:

# /usr/sbin/mksf -d asio0 -H 2/0/4 -a0 -i -v
        making cua0p0 c 1 0x000000

In both of these commands, the -d option specifies the device driver (asio0 in this case), the -H option specifies the hardware path (2/0/4 in this case), the -v option specifies verbose mode, and the -a option specifies the access mode (1 for a dial-out modem, 2 for a dial-in modem, and 0 for direct connect). The -i in the command for making a direct connect device, is used only for direct connect. For more information on these and other mksf options, see its manual page.

Dial-In Configuration

Edit the /etc/inittab to include an appropriate entry to run a getty process on the modem port. A typical entry looks like this:

ttp0:234:respawn:/usr/sbin/getty -h -t 240 ttyd0p0 9600

In the process field, the arguments to getty are as follows:

The -h option tells getty not to hang up the line before setting the port speed. This option is crucial for modems to work properly.
The -t 240 is a security option which requires that a login name and password is typed within 240 seconds of the port being opened. The number is configurable.
tty0p0 is the port to which the getty process attaches.
9600 specifies which port configuration to use from the gettydefs file. The entry will need to be changed, or possibly a new entry added to the gettydefs file for the modem used.

After modifying the inittab, issue the command init q to activate the changes.

The /etc/ttytype and /etc/gettydefs files are used the same as with terminals.

Dial-Out Configuration

Add an entry to the /etc/uucp/Devices file for the dial-out modem port's previously created device special file. Also, add a "Direct" line for debugging purposes. Devices file entries take the following form:

ACU device-file - speed dialer
Direct device-file - speed direct

For example:

ACU cul0p0 - 2400 hayes
Direct cua0p0 - 2400 direct

cul0p0 specifies the device special file to use when dialing out.
The 2400 represents the speed of the connection. Note, this is the connection between the modem and the computer, not between modems. The modem should negotiate a speed with the modem it connects to.
The hayes refers to an entry in the /etc/uucp/Dialers file which specifies the commands to be sent to the modem upon starting a connection.

Change these parameters to fit your modem, paying attention to what is allowed by the Dialers file (or, alternatively, make an addition to the Dialers file.

The modem should now be ready to dial-out. Use the command:

cu -s speed -l device-file telephone-number

replacing speed with the configured speed, device-file with the appropriate device special file, and telephone-number with the phone number to be dialed.

To make a direct connection to the modem for debugging, issue the command:

cu -s speed -l device-file -m dir

Terms used: device driver, UUCP.