Prevent SIGPIPE signal when writing to closed socket

[JohannesKauffmann]

By default, SIGPIPE will terminate the complete process. This is obviously not the ideal way to handle writing a closed socket. We already propagate EPIPE using the throw std::system_error. So, signal to the OS not to generate a signal.

The other option would be to install a signal handler for SIGPIPE, but that is not ideal inside a library.

[manter-international]

This only happens when the PLC closes the socket (for example when reprogrammed).
Fix tested, works. @JohannesKauffmann could you add some comments to the code?

[JohannesKauffmann]

Added some comments to explain what is being done.