Modem-HOWTO

• Index
• Introduction
• Modems for a Linux PC
• Modem Pools, RAS
• Serial Port and Modem Basics
• Configuring Overview
• Locating the Serial Port: IO address, IRQs
• Configuring the Serial Driver (high-level) "stty"
• Modem Configuration (excluding serial port)
• Serial Port Devices /dev/ttyS4, (or /dev/ttys/4) etc.
• Interesting Programs You Should Know About
• Trying Out Your Modem (Dialing Out)
• Dial-In
• Uugetty for Dial-In (from the old Serial-HOWTO)
• What Speed Should I Use with My Modem?
• Communications Programs And Utilities
• Two Modems (Modem Doubling)
• ISDN "Modems"
• Troubleshooting
• Flash Upgrades
• Other Sources of Information
• Appendix A: How Analog Modems Work (technical) (unfinished)
• Appendix B: Analog Voice Infeasible Over Non-Voice Modem
• Appendix C: "baud" vs. "bps"
• Appendix D: Terminal Server Connection
• Appendix E: Cable and DSL modems
• Appendix F: Connecting 2 Modems Directly Back-to-Back (Leased Lines).
• Appendix G: Fax pixels (dots)
• Appendix H: Stty Hanging Problem (prior to 2000)
• Appendix G: Antique Modems

15. Communications Programs And Utilities

While PPP is used for Internet access you also need a dialer program (or script) that will dial a phone number and then start PPP once a connection is made. When the other side answers the phone, then three things happen: a modem connection is established (CONNECT), PPP is started at both ends, and you get logged in automatically. The exact sequence of the last 2 events may vary. Dialer programs for ppp include wvdial, chap scripts, kppp, RP3 (front end to wvdial and ifup), gnome-ppp, and "modem lights" (Gnome). Linuxconf configures some dialers.

There are also older dialer programs which can dial out (via a modem) but don't connect to the Internet. Instead, you get connected to a computer somewhere that puts a text image on your screen. This was much used in the past to connect to Bulletin Boards. See PCs and BBSs Today, it might be used to connect to a remote computer that you may login to (including a PC at home). Programs for this are: minicom (the most popular), Seyon (X-Windows only) and Kermit. Some people have likely also used these programs for dialing out with ppp for the Internet but it's not what they were originally designed for.

15.1 Minicom vs. Kermit

Minicom is only a communications program while Kermit is both a communications program and a file transfer protocol. But one may use the Kermit protocol from within Minicom (provided one has Kermit installed on one's PC). Minicom is menu based while Kermit is command line based (interactive at the special Kermit prompt). While the Kermit program is free software, the documentation is not all free. There is no detailed manual supplied and it is suggested that you purchase a book as the manual. However Kermit has interactive online help which tells all but lacks tutorial explanations for the beginner. Commands may be put in a script file so you don't have to type them over again each time. Kermit (as a communications program) is more powerful than Minicom.

Although all Minicom documentation is free, it's not as extensive as Kermit's. In my opinion it's easier to set up Minicom, there is less to learn, and you can still use kermit from within Minicom. But if you want to write a script for automatically doing file transfers, etc. Kermit is better.

g-kermit is a gpled kermit which has no dialout capabilities.

15.2 List of Communication Software

Here is a list of some communication software you can choose from, If they didn't come with your distribution they should be available via FTP. I would like comparative comments on the dialout programs. Are the least popular ones obsolete?

Least Popular Dialout

• ecu - a communications program
• pcomm - procomm-like communications program with zmodem
• xc - xcomm communication package

Most Popular Dialout

• PPP dialers for getting on the internet: wvdial, eznet, chat, pon (uses chat),
• minicom - telix-like communications program. Can work with scripts, zmodem, kermit
• C-Kermit - portable, scriptable, serial and TCP/IP communications including file transfer, character-set translation, and zmodem support
• seyon - X based communication program

Fax

By using a fax program, you may use most modems to send faxes. In this case you dial out directly and not via ppp and an ISP. You also pay any long-distance telephone charges. email is more efficient.

• efax is a small fax program
• hylafax is a large fax program based on the client-server model.
• mgetty+fax handles fax stuff and login for dial-ins
• A fax protocol tutorial http://www.iec.org/online/tutorials/vfoip/topic08.html

Voicemail Software

• vgetty is an extension to mgetty that handles voicemail for some modems. It should come with recent releases of mgetty.
• VOCPis a "complete voice messaging" system for Linux.

Dial-in (uses getty)

• mgetty+fax is for modems and is well documented (except for voicemail as of early 1999). It also handles fax stuff and provides an alternative to uugetty. It's incorporating voicemail (using vgetty) features. See About mgetty
• uugetty is also for modems. It comes as a part of the ps_getty package. See About getty_ps

Network Connection

• ser2net
• sredird

Other

• callback is where you dial out to a remote modem and then that modem hangs up and calls you back (to save on phone bills).
• xringd listens for rings and detects inter-ring times etc.
• SLiRP and term provide a PPP-like service that you can run in user space on a remote computer with a shell account. See term and SLiRP for more details
• ZyXEL is a control program for ZyXEL U-1496 modems. It handles dialin, dialout, dial back security, FAXing, and voice mailbox functions.
• SLIP and PPP software can be found at ftp://metalab.unc.edu/pub/Linux/system/network/serial/.
• Other things can be found on ftp://metalab.unc.edu/pub/Linux/system/serial and ftp://metalab.unc.edu/pub/Linux/apps/serialcomm or one of the many mirrors. These are the directories where serial programs are kept.

15.3 SLiRP and term

SLiRP and term are programs which are of use if you only have a dial-up shell account on a Unix-like machine and want to get the equivalent of a PPP account (or the like) without being authorized to have it (possibly because you don't want to pay extra for it, etc.). SLiRP is more popular than term which is almost obsolete.

To use SLiRP you install it in your shell account on the remote computer. Then you dial up the account and run SLiRP on the remote and PPP on your local PC. You now have a PPP connection over which you may run a web browser on your local PC such as Netscape, etc. There may be some problems as SLiRP is not as good as a real PPP account. Some accounts may provide SLiRP since it saves on IP addresses (You have no IP address while using SLiRP).

term is something like SLiRP only you need to run term on both the local and remote computer. There is no PPP on the phone line since term uses its own protocol. To use term from your PC you need to use a term-aware version of ftp to do ftp, etc. Thus it's easier to use SLiRP since the ordinary version of ftp works fine with SLiRP. There is an unmaintained Term HOWTO.

15.4 MS Windows

If you want someone who uses MS Windows to dial in to your Linux PC then if they use:

• Windows 3.x: use Terminal
• Windows 95/98/2000: use HyperTerminal

Third party dial-out programs include HyperTerminal Private Edition.