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.

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

- 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

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>

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.

Reported by Viet Nguyen Quoc.

Introduced the select() operation for backends as the WAIT_DATA macro
approach is not very extensible and causes trouble when adding platform-
specific codepaths.

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

There are several header files that are already included in modbus.h
and thus do not have to be included in the C files.

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

The send() and recv() functions of the backends might require more
information than just a file descriptor, therefore pass the complete
modbus_t structure.

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

In modbus_flush() we should return the return value of the backend's
flush() function.

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

Renamed error_print() to _error_print() in order to indicate it's a
private method and make it globally accessible so functions in
modbus-rtu.c and modbus-tcp.c can make use of it as well.

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

All private functions and constants are now prefixed by _.
The modbus protocol uses entry points to call specific functions.

If <sys/time.h> is not included before "modbus.h" as struct timeval
is not declared. This behavior was observed while building libmodbus
for QNX.

Signed-off-by: Matthias Weisser <weisserm@arcor.de>

Idea suggested by Hannu Vuolasaho

- return only useful data client side
- available in TCP when a gateway to RTU is used
- need to add isolated handling of indication/confirmation messages

- more coherent
- namespace
- opaque and smaller context
- usual wording

A new API will be committed to remove the slave in TCP communication.

Original patch by Sisyph (eric-paul).