Peter M. Groen / libmodbus

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).

The function was used only one time.

The ID used at init time will be the device ID of the caller and
the server ID in request functions is the target to reach.

The library is now simpler to include (only one <modbus.h>)
To avoid confusion MB_VERSION defines have been renamed to
LIBMODBUS_VERSION.

This reverts commit df0cf7927249954f15e0aa85b02d21b990fa9af9.
Use <modbus.h> in tests.

This time the change is definitive :)

Requests not to send SIGPIPE on errors on stream oriented sockets
when the other end breaks the connection.

The previous implementation dereferenced a type-puned pointer, which is
illegal according to ANSI C. Some newer versions of GCC will complain
about this. This implementation uses "memcpy" to avoid this problem.

- the return value is used to pass the message length
- remove the hack on exception check in modbus receive
- update tests