modem - Describes guidelines for using modems
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-toPoint
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: Connections and Network Administration:
Services for specific information on SLIP, PPP,
and UUCP connections.
Using the Correct Modem Cables [Toc] [Back]
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 [Toc] [Back]
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 connected to. 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 system 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 command language, enter the
following command:
at<Return>
If the modem is not in quiet mode, it responds with
an OK message. 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) operation.
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 similar 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 create 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 thirdparty
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 [Toc] [Back]
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/acucap 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 following 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 system 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 follows:
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.
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)
[ Back ] |
