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By Al Alexander
If you've read the article "Using the cu Utility with Solaris 2.x" in our December 1995 issue, you may have started using the cu command to communicate with remote systems via a modem. In this article, we'll examine the process of configuring your Devices and Systems files to make using the cu program a little easier.
The command you'll use to dial out is called cu, for Call UNIX. This command is a part of a much larger communication facility known as UUCP, or UNIX to UNIX CoPy. The entire UUCP suite of tools allows you to perform remote logins to other systems, copy files to and from other sites, and send E-mail to remote users--all via modem connections.
UUCP is now standard on all UNIX platforms. On UNIX System V Release 4 systems, such as Solaris, it is also referred to as the Basic Networking Utilities, or BNU. Configuring your system for dial-out capability with the cu command is the beginning of the entire UUCP configuration.
In our original article, we didn't cover system configuration. Thus, if your system wasn't already configured for use with cu, you couldn't dial out. For a minimal configuration for dial-out capability, you only need to modify one UUCP file--/etc/uucp/Devices--to connect to the outside world. The /etc/uucp/Devices file tells the UUCP utilities which devices they can use to contact remote machines.
You can edit the Devices file with your favorite text editor.
Assuming that you have a Hayes-compatible modem connected to the
first serial port on your computer, add the following lines to
the end of the Devices file:
ACU ttya - Any hayes
Direct ttya - Any direct
Make sure there are no blank spaces at the beginning of these lines. Any line within the Devices file that begins with a blank will be considered to be a comment. Lines beginning with a # symbol are also considered comments.
Table A provides the definitions of
the fields in the Devices file. The first line we added
to the file specifies that an Automatic Calling Unit (e.g., a
modem) is connected to the serial line /dev/ttya, that
connections can be made at any speed, and that a Hayes-compatible
dialer program will be used to issue commands to the modem.
Table A
Field #/Description
1 Device type (either ACU or Direct)
2 Device to use for the connection
3 Dialer-line (this field is archaic; just use a "-")
4 Connection speed
5 Dialer-token (hayes uses the Hayes command set for dialing; Direct assumes a connection is already made and this field is not required.)
If you're using a Hayes-compatible modem on your serial port,
this configuration line lets you submit a phone number to the
cu command, and the
dialer program takes care of the rest of the work. For example,
the following command dials the phone number 568-6250:
# cu 5686250
The second line we added to the Devices file specifies that we also have a direct connection to the serial line /dev/ttya. You use this configuration line to allow direct access to the modem, in case you need to issue special commands, such as at or atz0.
Once you've made these changes to the Devices file, you
can connect to the modem directly with the command
# cu -lttya
where the -l command-line switch tells the cu program the device to which you want to establish a connection.
If this command succeeds, you'll see the message Connected
from the computer system. You can now type commands from the Hayes
command set, such as AT,
and your modem should respond with the usual OK message,
as shown below:
# cu -lttya
Connected
at
OK
If you see these messages, congratulations! You've done everything
you need to dial out from your system. If you make an error configuring
your Devices file, cu
may give you an error message like this:
# cu -lttya
Connect failed: NO DEVICES
AVAILABLE
If you don't see these messages displayed on your screen, it might be because your modem isn't turned on, your modem may be connected to the wrong port, the port may not be enabled properly, or you may be using an incorrectly-configured cable. Please read your modem's installation manual before proceeding any further.
Once you successfully configure your system, you can either try dialing out to another system with the ATDT or ATDP commands, or you can disconnect from the modem. To disconnect, type the special character sequence ~. (a tilde followed by a period) and press [Enter]. The system should respond with the Disconnected message and return you to your UNIX prompt.
The entire connection sequence should look like this:
# cu -lttya
Connected
at
OK
~voyager.
Disconnected
Take a look at the fifth line. While you typed only the character
sequence ~. the cu
program displayed the system name between the characters you typed.
With your current setup, you can call any computer in the outside
world by either specifying its phone number or connecting to the
ttya device and then issuing an ATDT or ATDP
modem command. If you change an additional UUCP configuration
file, you can call remote systems by name, such as
# cu compuserve
The file you'll need to change is called /etc/uucp/Systems. In this file, you specify the names of computer systems to which you may want to connect, as well as some additional information, like the phone number and connection type.
For instance, if your local CompuServe phone number is 568-6250,
you can add the following line to your Systems file:
compuserve Any ACU Any 5686250
Table B describes the field definitions
for the Systems file.
Table B
Field #/Description
1 Name of the remote site
2 Calling schedule--Any allows calls at any time of day; Never disallows callouts using this entry.
3 Device type (ACU or Direct)
4 Connection speed
5 Phone number of the remote site
6 Login conversation script (not used
in this article).
Please note that only the first seven letters of the remote site name are expected to be unique. Therefore, you must be careful when setting up the Systems file to ensure that no two site names start with the same two letters.
After you configure your Systems file, you can easily dial
in to CompuServe by typing
# cu compuserve
Once you've configured the Devices and Systems files,
you and every user on your workstation can dial out to remote
computer sites to run remote applications and transfer files.
An additional benefit is that you've begun to configure your entire
UUCP system. If your business has several geographically separated
offices, you can continue the UUCP setup to further enable scheduled
remote logins, file transfers, and site-to-site E-mail.
Alvin J. Alexander is an independent consultant specializing in UNIX and the Internet. He has worked on UNIX networks to support the Space Shuttle, international clients, and various Internet service providers. He has provided UNIX and Internet training to over 400 clients in the last three years.
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