modem(7)modem(7)NAMEmodem - Describes guidelines for using modems
DESCRIPTION
The Tru64 UNIX system enables you to use a variety of modems for point-
to-point connections to systems that are not in close proximity to each
other. These connections can be Serial Line Internet Protocol (SLIP),
Point-to-Point Protocol (PPP), and UNIX-to-UNIX Copy Program (UUCP)
connections. In addition, these connections can be basic dial-out/dial-
in connections (for example, to log in to a remote system to perform
remote system administration).
This section presents general guidelines for using modems on Tru64 UNIX
systems for all types of connections. See Network Administration: Con‐
nections and Network Administration: Services for specific information
on SLIP, PPP, and UUCP connections.
Using the Correct Modem Cables
In order to connect a modem to the serial port of your system, you must
use the correct cable. If you do not, you might experience signal loss,
resulting in the software not functioning properly. The following table
lists the cables you should use. The cable connector is either 25-pin
or 9-pin, depending on the type of serial port on your system. See the
hardware documentation for your system if you are unsure about the type
of serial port.
Note
OPEN DECconnect cables do not provide a sufficient number of wires for
full modem control. You should not use them for connecting modems to
the system.
──────────────────────────────────────────────────────────
Cable Number Description
──────────────────────────────────────────────────────────
BC22E-xx 16-wire modem cable (Male DB25 pin to
female DB25 pin cable)
BC22F-xx 25-wire modem cable (Male DB25 pin to
female DB25 pin cable)
BC29P-xx Male DB25 pin to female DB9 pin cable
PC modem cable Male DB25 pin to female DB9 pin cable
──────────────────────────────────────────────────────────
In the previous table, xx denotes the cable length. For example,
BC22E-10 is a ten-foot cable.
Configuring a System for Dial-In Access
After you have obtained the correct cable and connected your modem to
it and the telephone network, do the following: Edit the /etc/remote
file and create an entry similar to the kdebug entry. For example, if
your modem is connected to tty00 and you are going to use a baud rate
of 38400 to access the modem, create an entry similar to the following:
b38400:dv=/dev/tty00:br#38400:pa=none
Note
Some modems set their baud rate to the serial port rate. Be
sure to access the modem using the same baud rate that you are
going to specify to getty or uugetty. Otherwise, you might not
be able to log in because of a mismatch in baud rates.
See ports(7) if you are unsure which port your modem is con‐
nected to. Check the /usr/spool/locks directory for LCK..ttynn
lock files. If any exist for the terminal device you are config‐
uring for use with the modem, remove them.
When you establish a connection over a terminal device, the sys‐
tem generates a lock file to prevent the connection from being
disrupted by another application. If the connection terminates
abnormally, the lock file might persist, preventing you from
establishing new connections. Use the tip command to access the
modem as follows:
tip b38400
The tip utility responds with a connected message. You can now
communicate with the modem. If your modem is using the AT com‐
mand language, enter the following command:
at<Return>
If the modem is not in quiet mode, it responds with an OK mes‐
sage. Set the modem up for dial-in access. The following table
lists the AT commands required. Most of these command settings
are the default settings.
─────────────────────────────────────────────────────
Command Description
─────────────────────────────────────────────────────
at&c1 Normal Carrier Detect (CD) operation.
Tells the modem to not raise Carrier
Detect until it see Carrier Detect from
the other modem.
at&d2 Normal Data Terminal Ready (DTR) opera‐
tion. This is important in that it tells
the modem to hang up the line when DTR
drops. For example, when the user logs
off the system.
atq1 Sets the modem into quiet mode. Result
codes are not sent to the system.
ate0 Echo off. This prevents the modem from
echoing back the login prompt issued by
the getty process.
ats0=n Specifies the number of rings to wait
before answering. If n = 0 (zero), the
modem will not answer.
at&w0 Saves the current modem settings in NVRAM.
─────────────────────────────────────────────────────
The operating system supports both hardware and software flow
control. If the system supports hardware flow control, set the
modem and the serial line up to use hardware flow control by
using the appropriate commands. If hardware flow control is not
supported, you should use software flow control. Edit the
/etc/inittab file and create an entry for the modem. If you want
to use the modem line in non-shared mode, create an entry simi‐
lar to the following:
modem:23:respawn:/usr/sbin/getty /dev/tty00 M38400 vt100
If you want to use the modem line in shared mode (for dial-out
and dial-in connections), use uugetty instead of getty and cre‐
ate an entry similar to the following:
modem:23:respawn:/usr/lib/uucp/uugetty -r -t 60 tty00 38400
With uugetty, you will be able to use the tip and cu utilities,
but might not be able to use third-party utilities because of
differences in file locking.
Note
If you want to use the uugetty utility, you must install the
UNIX-to-UNIX Copy Facility subset. As root, start the getty or
uugetty process by entering the following command:
init q
The getty or uugetty process starts, then goes to sleep, waiting
for someone to dial into the system.
Configuring Your System for Dial-Out Access
After you have obtained the correct cable and connected your modem to
it and the telephone network, do the following: Verify that there is an
entry for the modem name specified with the modemtype subcommand in the
/etc/acucap file. If your modem does not have an entry in the /etc/acu‐
cap file, do the following: Copy an entry similar to that of your
modem. The following entry is for a US Robotics modem for use in
shared mode with tip:
us|US|US Robotics (28.8 fax/data modem):\
:cr:hu:ls:re:ss=AT\rATE1Q0&C0X0&A0\r:sr=OK:\
:sd#250000:di=ATD:dt=\r:\
:dd#50000:fd#50:os=CONNECT:ds=\d+++\dATZ\r\dATS0=2\r:\
:ab=\d+++\dATZ\r\dATS0=2:
Be sure the entry includes at least the AT commands in the fol‐
lowing table. The other modem settings can remain as they are.
─────────────────────────────────────
Command Description
─────────────────────────────────────
ate1 Turns on echoing.
atq0 Displays the result codes.
─────────────────────────────────────
Modify the modem attributes to match your modem's attributes and
include the debug option (db). With debugging turned on, the
modem will provide you with additional information with which to
tune the modem attributes in the file. See acucap(4) for more
information. Create an entry in the /etc/remote for the system
you want to call. Among the information you can supply is the
Tru64 UNIX device, baud rate, and /etc/acucap that defines your
modem. The following two entries are for the modem specified in
step 1a.
tip38400:tc=us38400 us38400|38400 Baud dial out via US Robotics
modem:\
:el=^U^C^R^O^D^S^Q@:ie=#%$:oe=^D:\
:dv=/dev/tty00:br#38400:ps=none:at=us:du:
In the previous example, the first line is an entry that points
to the us38400 entry specifying shared capabilities for modems.
The second line is the first line of the us38400 entry. The
third line defines end-of-line characters, and input and output
end-of-file marks. The fourth line defines the UNIX device to
open for the connection, the baud rate, the parity, the name of
the /etc/acucap file entry, and the dial-up line.
See remote(4) for more information. If you use getty to provide
access to the system from a modem and a getty process is already
running, do the following: Edit the /etc/inittab file and put a
comment character (#) at the beginning of the modem entry.
Issue the init q command to terminate the getty process. Check
the /usr/spool/locks directory for LCK..ttynn lock files. If any
exist for the terminal device you are configuring for use with
the modem, remove them.
When you establish a connection over a terminal device, the sys‐
tem generates a lock file to prevent the connection from being
disrupted by another application. If the connection terminates
abnormally, the lock file might persist, preventing you from
establishing new connections. Use the tip command, specifying
the -baud_rate flag and the telephone number to dial out as fol‐
lows:
tip -38400 8881234
In this example, tip strips off the minus sign (-) from the baud
rate and concatenates the tip command name and the baud rate to
create the string tip38400. Then, tip searches the /etc/remote
file for the entry matching the string. The entry in the
/etc/remotes file, points the capability information in the
us38400 entry to initialize the modem.
By specifying the telephone number on the command line, you can
share the same modem attributes for outgoing connections that
have different telephone numbers.
When you log off the remote system and exit tip, the modems
saved settings are restored, readying the modem for the next
user. If used in shared mode, the modem is available for dial-
in access.
SEE ALSO
Commands: cu(1), tip(1), getty(8), uugetty(8)
Files: acucap(4), inittab(4), remote(4)
Devices: ports(7)
Network Administration: Connections, Network Administration: Services
modem(7)
