Peter M. Groen / libmodbus

Page 38 in the document Modbus_Application_Protocol_V1_1b.pdf:
6.17 23 (0x17) Read/Write Multiple registers

This function code performs a combination of one read operation
and one write operation in a single MODBUS transaction. The write
operation is performed before the read.

The unit test has been updated.

Original patch by Jason Oster

Win32 uses a specific function to close socket.
Reported by Petr Parýzek.

Reported by Ivo De Decker

Reported by Antti Manninen and according to Page6 in the document
"MODBUS Messaging on TCP/IP Implementation Guide V1.0b",
------------------------
Unit Identifier – This field is used for intra-system routing purpose.
It is typically used to communicate to a MODBUS+ or a MODBUS serial
line slave through a gateway between an Ethernet TCP-IP network and
a MODBUS serial line. This field is set by the MODBUS Client in the
request and must be returned with the same value in the response by
the server.
------------------------

Contributed by Dominic Storey.
- new function modbus_reply_exception
- unit test

- MODBUS_GET_INT32_FROM_INT16
- MODBUS_GET_INT16_FROM_INT8
- MODBUS_SET_INT16_TO_INT8
- check the trame length before indexing in unit-test-server

- new public function
- change unit-test-server.c to be transport layer independant (query
  and header_length)

The goal of this rewriting is to avoid the timeouts on the receiving
of exceptions and to be more robust on bad requests. Some devices
use the exception MODBUS_EXCEPTION_ACKNOWLEDGE to response to some
valid requests, so in this case, you'll really appreciate this
change!

- Slower! More system calls are used.
- The code is cleaner and easier to understand.
- Really faster when an exception occurs.
- Fix unit test of bad request in RTU

- removed comment not required anymore with -Wall -Werror

Reported by Ivan Giuliani <giuliani.v@gmail.com>
It was not possible to use libmodbus outside of projects without
config.h file.

The inclusion has been removed from the public header.

Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

First, it's $host_os which should be checked, not $target (remember,
'build' is where we build, host is where the program will be run, and
target is only for compiler - for which system the compiler will
generate code.

Second, correct OS pattern - e.g. on debian with i586-mingw32msvc-gcc,
host_os is mingw32msvc, so we better for *mingw32*.

Also, it's better to call AC_CANONICAL_* for normalizing variables.

Build tested with `configure --host=i586-mingw32msvc` on Debian
GNU/Linux 5.0 (Lenny).

Cc: Александр Сёмуха <sav@mns.spb.ru>
Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Stéphane Raimbault <stephane.raimbault@gmail.com>

These functions have no meaning in RTU so it's better to specialize
the names and remove them from the backend.

- remove the functions from the backend
- update tests to handle RTU mode (master and slave)
- add command line options to tests (rtu or tcp)

- check strlcpy in configure.ac
- test for empty device string
- test truncated device string

When unitialized the socket can be 0 and write calls success.

modbus_set_slave must be used to set the slave ID of the remote
device to talk in master mode and to set the internal slave ID in
slave mode.

If you talk to several devices, you need to call modbus_set_slave
each time the following requests must be sent to another device.

- move termios header in RTU backend
- move TCP headers in TCP backend
- use native serial on Win32 for Cygwin
- avoid too many defines

This change fixes a compilation problem in MinGW. As general rule,
each header must be as independent as possible.

I prefer to remove the check rather than to add the solution used
by Wine as we don't care about the associated define:

AC_CHECK_HEADERS([ \
    ...
    netinet/ip.h \
    netinet/tcp.h \
    ...
],,,[
    #ifdef HAVE_NETINET_IP_H
    # include <netinet/ip.h>
    #endif
])

This change is asked by Barry Grumbine to fix build on OpenBSD