Peter M. Groen / libmodbus

- check conversion
- display IP in in IPv6

Thank you @pboettch for initial proposal.

Useful functions when you are confronted with equipment which does
not respect the protocol, which behaves strangely or when you wish
to move away from the standard.

Thank you @mhei for the great initial version.

previous test would fail if one byte was non zero.

- allocate exact memory required to store node and service strings
  instead of around 1kb of static memory.
- accept NULL value of service to use default Modbus port number (502)
- unit test updated

The new documentation will be updated in another commit.

Thanks to @peternewman

Since SPDX release 3.0 LGPL-2.1+ became LGPL-2.1-or-later. Hence
replace the deprecated identifiers.

Signed-off-by: Richard Genoud <richard.genoud@gmail.com>

fixed small typo

Current code could dereference NULL pointer in case an inner
malloc fails. Check for this and exit gracefully.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

The socket management belongs to the application.

The return code was missing in modbus_tcp_pi_accept().

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

This replaces the lengthy license text headers with a short
and standardized license tag. See http://spdx.org for details.

This is useful e.g. for license compliance tools which scan
through files and generate a report of the licenses used
in a project.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

Thank you Petr Gladkiy and MarjanTomas.
Sorry for the delay...

From Michael Heimpold:
Just a nitpick: the INADDR_* macros are defined in host byte order,
compare INADDR_LOOPBACK. So it would be reasonable to wrap this with
htonl(INADDR_ANY). However, every experienced socket programmer should
know that INADDR_ANY equals 0.0.0.0, passing it through htonl does not
have any effect.

- protect against NULL IP address BTW
- update documentation

- allow an empty string or NULL for node argument
- protect against NULL in service argument
- new test for NULL service
- update documentation

Thanks to Perry Kundert for bug report and initial patches.

- change return argument from void to int
- update documentation