Category : Communication (modem) tools and utilities
Archive   : NMODM215.ZIP
Filename : NMODEM.DOC

NMODEM 2.14 DOCUMENTATION
-------------------------

NMODEM is a file transfer protocol written in Turbo C++ 1.01 for the
"IBM" family of computers.

This protocol sends data in 2048k blocks. The last block will be the size
of the final bytes in the file, thus the original file size will be
retained. Each block has an overhead of 6 bytes.

2048 bytes was chosen for block size as it seems to be the optimum size for
CPS and minimal impact on efficiency if an error should occur. It also
happens to be the normal size of a Hard Drive sector, 2 times a Floppy
sector and 1/2 of a oversize Hard drive sector thus improving disk
read/write efficiency.

NMODEM uses 16-bit CRC error checking for a very high reliability of
successful transfer in rough conditions with minimal transfer overhead.

LEGAL STUFF
-----------

NMODEM is Copyright (c) 1990,1991 by L.B. Neal. All Rights Reserved.

Anyone may distribute the NMODEM cheapware version as long it is unmodified,
complete and any distribution fee is less than $5.00.

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NOTE: The registered version of NMODEM may NOT be distributed excepting
to SYSOPs of "NOT-for-Profit" BBS systems. See Caution.TXT.
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NMODEM is distributed as "cheapware". You may try this program to see
if it is of value to you before registering. If you find the product
to be of value you MUST pay the registration fee or stop using the program.
SYSOPS of non-profit BBS's may use NMODEM without registration.

If you paid a fee for NMODEM to anyone but L. B. Neal you did NOT register
NMODEM you paid for media and handling costs.

Registration schedule is as follows:

1. Register NMODEM but w/o disk $ 5.00

2. Register NMODEM w/returned registered version - $10.00
* Has DirectVideo/FIFO/Sound/No Log options enabled.
* Latest Version plus latest NMTERM program.
* Misc items that will also fit on disk.

3. Update registered version by mail. $ 2.00

4. Update registered source by mail. $ 5.00

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NOTICE: Registered users will be able to download the latest registered
version from PYSMATIC or THE COMM CENTER for free!!

I will need your user#, Password and which BBS you use
to set up access!
--------------------------------------------------------------------

NOTE: Items 2,3 & 4 include media, handling, postage and Tax!

My mailing address is currently:

L.B. Neal
415-112 N. Mary Ave #111
Sunnyvale, CA 94086

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NMODEM is provided AS-IS without warranty!

I am NOT and will NOT be responsible for the use or misuse of this program.

It is my belief that this program will function essentially as described
in this document but I cannot test for every possible software/hardware
configuration.

If you use this program then you have agreed to the previous statements.
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The source code for NMODEM is available for $60. If you purchase the
source you will be required to sign a Non-Disclosure agreement and will
NOT be allowed to distribute any modified form of NMODEM or the source
code. You will be able to utilize modified versions for your own use.
This provision is for the protection of myself and other users and is NOT
intended to prohibit individuals or organizations from adjusting the program
for specific needs. Individuals or organizations wishing to incorporate
NMODEM into a communications program should contact me directly for very
nominal licensing fees.

NOTE: Due to the low registration cost of NMODEM - Registration or
purchase of the source does NOT in anyway require any support for
the program by L.B. Neal. However, I will address problems reported
in a prompt manner.


USAGE NOTES
-----------

1. NMODEM assumes the comport called for is already initialized.
Therefore using NMODEM directly from DOS will probably NOT work!

2. A minimum of 45k of free memory is needed to sucessfully operate.

3. COM1 thru COM4 are supported with 3 & 4 setup for the "unofficial"
standard as used by Everex and other manufactures.

4. NMODEM will exit with a DOS error level of 1 if anything goes wrong.
Otherwise the value will be 0.

5. Please report "in detail" any problems experienced in using the program.

6. Call NMODEM w/o parameters ie C:\>NMODEM or such to see the needed
info for using.

NMODEM needs:

a. S for Send or R for Receive.

b. port# (COM1 thru COM4)

c. FileName to transfer.
optional drive and/or directory.

d. If you add the /D behind the filename Directvideo will be used.
* [registered versions]

e. If you have a 16550 UART a /F behind the file name will enable
the UART FIFO Buffer.
* [registered versions]

f. NMODEM.LOG is disabled with /L - NMODEM will NOT write to
nmodem.log.
*[registered versions]

g. Short beeps at the end of transfer is enabled with /S.
* [registered versions]


Examples:

"cheapware" version:

NMODEM S2 Myfile.zip { Send via COM2: myfile.zip }
NMODEM S1 c:\uploads\Myfile.zip { Send via COM1: myfile.zip }
NMODEM R2 c:\download\Hisfile.zip { Recv via COM2: hisfile.zip }
NMODEM R1 Hisfile.zip { Recv via COM1: hisfile.zip }

Registered version:

NMODEM S2 C:\UPLOADS\Myfile.zip /D { Send via COM2: myfile.zip }
NMODEM S1 C:\UPLOADS\Myfile.zip /DF { Send via COM1: myfile.zip }
NMODEM R2 C:\DOWNLOAD\Hisfile.zip /D { Recv via COM2: hisfile.zip }
NMODEM R1 C:\DOWNLOAD\Hisfile.zip /F { Recv via COM1: hisfile.zip }


NOTE: I have set up NMODEM to use the same basic parameter string as
JMODEM to make it easier to install. If you have a JMODEM batch
file just rename it and change JMODEM to NMODEM inside the batch
file.

Combined switches are just added behind a single '/'!


7. I have taken great care to try to make sure the CPS rate reported is
accurate (Unlike many other protocol drivers!). Please advise if you
find my efforts in vain. I recently performed stopwatch tests with
large file transfers and the indicated CPS did infact match the size
vs time.


NOTE: The CPS calculation does NOT include receive file I/O time. It
does include resend times if necessary. It is not unusual to see
a low CPS for the first block depending on the interface timing.
The receive IO is in the background and thus does NOT normally
effect the actual CPS.

8. NMODEM will resend a block 6 times before aborting the effort.

9. This program plays no tricks and assumes the calling program is nice
as well. Tricky programs will probably cause NMODEM to fail.

10. NMODEM in Turbo Pascal would allow writing Runtime errors to the
Nmodem.err file, however Turbo C++ presents a very complicated
method for trying to determine Runtime problems. Therefore the "C"
version (2.00 and higher) will NOT attempt to write Runtime errors
to the file.

11. NMODEM uses BIOS screenwrites for maximum compatability with DesqView
and other Multi-Tasking situations. The registered version has an option
for enabling DirectVideo. IF you must use the BIOS method I suggest you
investigate QCRT11.ZIP for much faster screenwrites!

12. I have provided NMR.BAT and NMS.BAT as sample batch files which are setup
for parameters as passed by TELIX.

12. If you attempt to receive an existing file NMODEM will abort!

14. If NMODEM aborts during a receive operation the file will be deleted.

15. NMODEM has been tested with TELIX 3.15 and QMODEM 4.2 they seem to work
fine. I also tested with GT-1550 and was unable to duplicate problems
reported by some GT users.

16. Remember TSR's can have strange side effects. If NMODEM fails please
address any TSR's in your system as a possible cause of the problem.

17. NMODEM has been tested with MS-DOS 4.01 (later version or w/patch),
OS/2, DR-DOS 5.0, PC-MOS 4.1, DOS-XM 6.2, Concurrent DOS-386 3.0 and
MS-DOS 5.0.

18. NMODEM will NOT work below 1200 Baud!

19. Computers which do NOT have DMA such as PCJr and some versions of the
TANDY 1000 will NOT work with NMODEM.

20. Special thanks to Ted Chan, Dennis King, Ron Pierce and
Dave Halliday for their help with BETA testing of NMODEM.

21. A user recently reported that NMODEM would NOT work due to a problem
with his floppy controller card. "Anything can cause problems".

22. Starting with version 2.09, I am providing NMODM286.EXE which will
run only on 80186/80286/80386/80486 computers. This version takes
advantage of special instructions available only on these CPUs.

23. I am happy to report that several users of NMODEM who regularly
frequent PYSMATIC BBS have advised me that NMODEM is the fastest
protocol they have used. BTW: PYSMATIC runs a 10Mhz XT-clone and
thus is NOT dependent on super CPU thruput.

24. I can be contacted at:

THE COMM CENTER
(415)967-3802

PYSMATIC BBS
(415)969-4159

Both in Sunnyvale, CA


TECHNICAL NOTES
---------------

1. NMODEM does NOT use assembly language to improve transfer speed.
Standard Turbo C++ library routines are used for IO. Also, I do
NOT use the several "COMM libraries" that I own since they use
specialized assembly routines for speed.

2. The port initialization routines use some assembly features as
provided by Turbo C++ since the nature of the beast requires some
of these methods.

3. An interrupt driven receive buffer is utilized to allow high speed
transfer without dropping bytes. The buffer is NOT written in
assembly language or inline. Specific items are called in psuedo
assembly, but are NOT related to the buffer efficiency but just
the need to enter and exit the interrupt properly.

4. Output is directly via the port and a buffer is not used.

5. The program is constructed to avoid Procedure and Function calls
in the transfer routines for efficiency. All transfer variables are
global to avoid stack manipulation overhead.

6. Great care has been taken to use only standard DOS and BIOS interface
calls to avoid wierd side effects in using NMODEM. The program is
being used under FALCON BBS, WILDCAT! BBS, FEATHERNET BBS, TMODEM,
TELIX 3.15 and QMODEM 4.2 on XT, AT & 386 class machines of various
manufacture and working well. Some users have experienced problems
with lockups, inability to synchup, etc. At this point I must suspect
TSR type interference though it is possible I have overlooked a step in
the interrupt interface. This aspect is under constant review to attempt
to uncover any oversights on my part.

NOTE: Version 2.01+ has a completely rewritten modem interface which
should resolve most problems!

7. As of version 1.20 the file lookahead scheme was removed since it was
faulty and did NOT work when an error was encountered. I will try to
come up with a new scheme that will work.

8. Version 1.30 fixes a bug introduced by me and considerable change in
the main Send and Receive procedures.

9. Version 1.31 uses a new status screen scheme and improves on handling
of NMODEM.ERR and NMODEM.LOG files.

10. Version 1.32 eliminates redundant ClearScreen.

11. Version 1.40 changes the modem interface hopefully for the better!
NMODEM now uses Turbo Pascal 5.5, TPCRT from Turbo Power Software,
and SYST55C2 from Eagle Performance Software! Each of these items
increase the speed of NMODEM!

12. Version 1.41 introduces a 1 sec delay after setting up the UART to
allow slow UARTS to process the information.

13. Version 1.50 introduces yet another major revision of the modem
interface to try to improve reliabilty with various modems.

14. Version 1.60 eliminates the restiction on path names in the shareware
package. I also optimized send and receive loops. NMODEM will now
inform DOS of COM3: and COM4: while operating and restore the initial
status on exit.

16. Version 1.61 introduces an option to disable the generation of the
Nmodem.log file. This option works on registered versions only!

17. Version 1.62 adds these features:

A. Added statusline that shows the various options.

B. Optimized the status screen.

C. Cleared full status screen on exit.

18. Version 1.63 addresses some code typo errors on my part and adds
some code to handle interrupts better.

19. Version 1.64 tweaks the interrupt interface and reduces memory needs
by 4k.

20. Version 1.65 will place date and time stamp in all NMODEM.LOG and
NMODEM.ERR entries. Also reduced lines entered into NMODEM.LOG.

21. Version 1.66 corrects a goof in the new status window drawing
scheme.

22. Version 2.00 is now compiled with Turbo C++ 1.01. It will soon be
compiled with TopSpeed C++ 3.01 or Zortech C++ 3.0.

23. Version 2.01 uses a totally new modem interface scheme!

24. Version 2.02 corrects clearing status screen, adds beep option at
end of transfer and improves CPS calculation. MNP "support" was
removed since the scheme was basically faulty and did NOT really
improve transfer speed, the CRC check will be made at all times.

25. Version 2.03 eliminates echo of keys hit to screen.

26. Version 2.04 will now delete aborted receive files.

27. Version 2.05 corrects flaw in the syncup routine to force
a 60 second delay. Corrects exit flag routine and changes some
#define statements to typedef.

28. Version 2.06 speeds up status window display.

29. Version 2.07 addresses an "ambiguous" return from fread()
at END-OF-FILE with TC++.

30. Version 2.08 speeds up CRC calc routine. The code is NOT the best
but I have yet to a figure a way to trick the compiler into making
it faster. The tricks that cause Turbo Pascal to generate the good
code are not recognized by TC++.

The CRC calc is faster by using doubles for all floating point calcs.
Seems TC++ does multiple conversions from float to double when
using floats.

NOTE: The large size of NMODEM.EXE is a result of TLINK NOT being
very "smart" with C code! Adding floating point to get
accurate CPS calculations brought in the whole world! In
Turbo Pascal the penalty is about 2k. In TC++ the penalty
is about 12K!

Using NMODEM 2.0+ with a floppy drive will result in very
poor transfer rates. This is because the fread() and fwrite()
functions are very slow when addressing non-HD media.

31. Version 2.09 solves the display problem for the final short block in
a transfer. A 80286 version is now supplied as NMODM286.EXE. This
version will take advantage of improved CPU instructions.

32. Version 2.10 uses some TC++ features to improve speed one more
time. Specific efforts are in the modem interrupt handler and
the keyboard monitor.

33. Version 2.11 tuned the buffer interrupt one more time.

34. Version 2.12 restores the old mode of looking for keys pressed
by the user. The BIOS system introduced in 2.10 may be causing
some problems.

35. Version 2.14 addresses use with 9600 bps modems.