fixd: when restore command, "topics" no malloc.

fix issue that MQTTClient_connect hangs on network outage, for windows

Signed-off-by: LeonLi <liting6680@gmail.com>

Signed-off-by: ubyyj <wdyuanyoujun@163.com>

Remove shadow warning and improve consistency

Fix Socket_setnonblocking() for Windows (At least if build with MSVC …

Signed-off-by: Juergen Kosel <juergen.kosel@softing.com>

Partially revert commit a16cff63 for file
src/Socket.c

- Do not include errno.h for Windows build
- Use errno as a local variable in Socket_setnonblocking() for Windows
Signed-off-by: Juergen Kosel <juergen.kosel@softing.com>

Don't shadow already defined variable (data_size).
In addition, we are consistence with the case statement
above.
Signed-off-by: Niklas Johansson <niklas.johansson@prevas.dk>

Add support for selecting/enforcing a TLS version

SSL/TLS: Add support for enforcing a TLS version through a new sslVersion field in the MQTTClient_SSLOptions structure. This affects which *_client_method() function is called in SSLSocket.c: 0 (default) -> SSLv23_client_method(), 1 -> TLSv1_client_method(), 2 -> TLSv1_1_client_method(), 3 -> TLSv1_2_client_method()
Signed-off-by: Günter Obiltschnig <guenter.obiltschnig@appinf.com>