sz.doc

支持ZModem协议的串口通讯程序

     SSSSZZZZ((((1111))))		OOOOmmmmeeeennnn TTTTeeeecccchhhhnnnnoooollllooooggggyyyy	IIIINNNNCCCC ((((OOOOMMMMEEEENNNN))))		 SSSSZZZZ((((1111))))



	  security check.

	  %%%% sssszzzz ----YYYYaaaannnn ****....cccc	****....hhhh
	  Send only the	.c and .h files	that exist on both systems,
	  and are newer	on the sending system than the corresponding
	  version on the receiving system, converting Unix to DOS text
	  format.

	  ZZZZMMMMOOOODDDDEEEEMMMM CCCCoooommmmmmmmaaaannnndddd DDDDoooowwwwnnnnllllooooaaaadddd (Unix	to Professional-YAM)
	   cpszall:all
	      zcommand "c:;cd /yam/dist"
	      sz -ya $(YD)/*.me
	      sz -yb y*.exe
	      zcommand "cd /yam"
	      zcommandi	"!insms"
	  This Makefile	fragment uses zzzzccccoooommmmmmmmaaaannnndddd to issue	commands to
	  Professional-YAM to change current disk and directory.
	  Next,	sssszzzz transfers the ._m_e files from	the $YD	directory,
	  commanding the receiver to overwrite the old files and to
	  convert from Unix end	of line	conventions to PC-DOS
	  conventions.	The third line transfers some ._e_x_e files.  The
	  fourth and fifth lines command Pro-YAM to change directory
	  and execute a	PC-DOS batch file _i_n_s_m_s	. Since	the batch file
	  takes	considerable time, the zzzzccccoooommmmmmmmaaaannnnddddiiii form is used to allow
	  the program to exit immediately.

	  XXXXMMMMOOOODDDDEEEEMMMM FFFFiiiilllleeee TTTTrrrraaaannnnssssffffeeeerrrr (Unix to	Crosstalk)
	  % ssssxxxx ffffoooooooo....cccc
	  EEEESSSSCCCC
	  rrrrxxxx ffffoooooooo....cccc
	  The above three commands transfer a single file from Unix to
	  a PC and Crosstalk.  This combination	is much	slower and
	  less reliable	than ZMODEM.

     EEEERRRRRRRROOOORRRR MMMMEEEESSSSSSSSAAAAGGGGEEEESSSS
	  "Caught signal 99" indicates the program was not properly
	  compiled, refer to "bibi(99)"	in rbsb.c for details.

     SSSSEEEEEEEE AAAALLLLSSSSOOOO
	  rz(omen), ZCOMM User's Manual, Professional-YAM User's
	  Manual, crc(omen), sq(omen), todos(omen), tocpm(omen),
	  tomac(omen), yam(omen)

	  Compile time options required	for various operating systems
	  are described	in the source file.

     FFFFIIIILLLLEEEESSSS
	  32 bit CRC code courtesy Gary	S. Brown.

	  sz.c,	crctab.c, rbsb.c, zm.c,	zmr.c, zmodem.h	Unix source
	  files




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     SSSSZZZZ((((1111))))		OOOOmmmmeeeennnn TTTTeeeecccchhhhnnnnoooollllooooggggyyyy	IIIINNNNCCCC ((((OOOOMMMMEEEENNNN))))		 SSSSZZZZ((((1111))))



	  /tmp/szlog stores debugging output (sz -vv)

     TTTTEEEESSSSTTTTIIIINNNNGGGG FFFFEEEEAAAATTTTUUUURRRREEEE
	  The command "sz -T file" exercises the AAAAttttttttnnnn sequence error
	  recovery by commanding errors	with unterminated packets.
	  The receiving	program	should complain	five times about
	  binary data packets being too	long.  Each time sssszzzz is
	  interrupted, it should send a	ZDATA header followed by
	  another defective packet.  If	the receiver does not detect
	  five long data packets, the AAAAttttttttnnnn sequence is not
	  interrupting the sender, and the MMMMyyyyaaaattttttttnnnn string in sssszzzz....cccc must
	  be modified.

	  After	5 packets, sssszzzz stops the	"transfer" and prints the
	  total	number of characters "sent" (Tcount).  The difference
	  between Tcount and 5120 represents the number	of characters
	  stored in various buffers when the Attn sequence is
	  generated.

     SSSSEEEERRRRVVVVEEEERRRR////NNNNEEEETTTTWWWWOOOORRRRKKKK NNNNOOOOTTTTEEEESSSS
	  Terminals on some timesharing	systems	are connected
	  indirectly to	the host with TTTTEEEERRRRMMMMIIIINNNNAAAALLLL SSSSEEEERRRRVVVVEEEERRRRSSSS operating over
	  networks.  Terminal servers often interfere with file
	  transfers by "eating"	control	characters and/or losing data.

	  When terminal	servers	interfere with file transfers, server
	  commands are often available to help the problem.  When
	  possible, enable the server and modems for hardware flow
	  control in and out.  Set the terminal	server to telnet
	  transparent mode.  Some typical commands are "SET TERMINAL
	  DOWNLOAD" and	"SET TERMINAL NO ESC", but there is no
	  standard set of commands suitable for	all terminal servers.

	  Escaping control characters (sz -e) may help if the transfer
	  gets stuck in	the same place on every	attempt.
	  Professional-YAM and ZCOMM allow selection of	which control
	  characters need to be	escaped.  In extreme cases 7-bit
	  transmission may be required (see the	Professional-YAM/ZCOMM
	  manual).

	  If you encounter problems with control characters Please
	  refer	to the sz -T command in	sz.doc for more	help.

	  Flow control between the server and modem is often
	  defective.  This rarely causes a problem in interactive
	  applications whose short bursts (a screenfull	at most) fit
	  within the available memory buffers.	Streaming protocols
	  such as YMODEM-g, long packet	SuperKermit, and ZMODEM	can
	  overload the available buffering.  Some terminal servers
	  support commands to enable hardware flow control such	as
	  "TERM	FLOWCONTROL HARDWARE IN	OUT"; this assumes the modem
	  attached to the server is properly configured.



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     SSSSZZZZ((((1111))))		OOOOmmmmeeeennnn TTTTeeeecccchhhhnnnnoooollllooooggggyyyy	IIIINNNNCCCC ((((OOOOMMMMEEEENNNN))))		 SSSSZZZZ((((1111))))



	  If the terminal server is too	brain damaged to support flow
	  control, you can fake	it with	ZMODEM.	 Try "sz -
	  w1024	file..." to enable software flow control. Experiment
	  with different values	to find	the best throughput.

	  Terminal servers are designed	to accept keyboard input from
	  human	operators.  They may lose data when a program sends
	  data to the host faster than humans type.  Some servers
	  allow	larger input buffers to	support	file uploads.  If you
	  can upload short files (less than 100	bytes) but not longer
	  files, try "sz -w1024	file..." with your uploading program.
	  (Not all programs support this option; use ZCOMM or
	  Professional-YAM.)

	  When both flow control and character transparency are
	  problems, use	"sz -ew1024 file..." as	a starting point.

	  Sometimes the	terminal server	software is defective and must
	  be upgraded.	Please contact the network's vendor for
	  corrective procedures.  An alternative is to install direct
	  serial ports for users desiring to upload files.

	  Some systems enforce a timeout which disconnects a user
	  after	several	minutes	of no keyboarding.  This can cause
	  problems in long, error free ZMODEM transfers.  Restricting
	  the window size with a "-w8192" option provides terminal
	  input	at regular intervals even when no error	correction is
	  needed.  If problems persist,	try setting a packet length
	  (sz -l1024).

     NNNNOOOOTTTTEEEESSSS
	  Particular attention must be paid to flow control.  The
	  modem	and Unix must agree on the flow	control	method.	 Sz on
	  USG (SYS III/V) systems use XON/XOFF flow control.  Some
	  terminal servers do not provide working flow control.	 If
	  flow control cannot be properly set up,
	  Try a	"-w1024" option	(given to the sending program) to
	  enforce protocol level flow control.	Experiment with
	  different window sizes for best results.

	  Telebit modems must not be set to "spoof" UUCP, XMODEM,
	  YMODEM, or KERMIT.  Setting one of these spoofing modes
	  interferes with other	protocols.  Telebit's YMODEM spoofing
	  interferes with YMODEM transfers.

	  If a program that does not properly implement	the specified
	  file transfer	protocol causes	_s_b to "hang" the port after a
	  failed transfer, either wait for _s_b to time out or keyboard
	  a dozen Ctrl-X characters.  Every reported instance of this
	  problem has been corrected by	using ZCOMM, Pro-YAM, DSZ, or
	  other	program	with a correct implementation of the specified
	  protocol.



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     SSSSZZZZ((((1111))))		OOOOmmmmeeeennnn TTTTeeeecccchhhhnnnnoooollllooooggggyyyy	IIIINNNNCCCC ((((OOOOMMMMEEEENNNN))))		 SSSSZZZZ((((1111))))



	  Many programs	claiming to support YMODEM only	support	XMODEM
	  with 1k blocks, and they often don't get that	quite right.
	  XMODEM transfers add up to 127 garbage bytes per file.
	  XMODEM-1k and	YMODEM-1k transfers use	128 byte blocks	to
	  avoid	extra padding.

	  YMODEM programs use the file length transmitted at the
	  beginning of the transfer to prune the file to the correct
	  length; this may cause problems with source files that grow
	  during the course of the transfer.  This problem does	not
	  pertain to ZMODEM transfers, which preserve the exact	file
	  length unconditionally.

	  Most ZMODEM options are merely passed	to the receiving
	  program; some	programs do not	implement all of these
	  options.

	  Circular buffering and a ZMODEM sliding window should	be
	  used when input is from pipes	instead	of acknowledging
	  frames each 1024 bytes.  If no files can be opened, sssszzzz sends
	  a ZMODEM command to echo a suitable complaint; perhaps it
	  should check for the presence	of at least one	accessible
	  file before getting hot and bothered.

	  Unix Professional-YAM	provides higher	performance and	other
	  features not supported by _s_z.	Please contact Omen Technology
	  Inc for product information.

	  Omen Technology INC
	  503-621-3406
	  Post Office Box 4681
	  Portland OR 97208


     BBBBUUUUGGGGSSSS
	  On at	least one BSD system, sz would abend it	got within a
	  few kilobytes	of the end of file.
	  Using	the "-w8192" option fixed the problem.	The real cause
	  is unknown, perhaps a	bug in the kernel TTY output routines.

	  The test mode	leaves a zero length file on the receiving
	  system.













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