Fix Global Socket write()

[clauspruefer]

Current Result Processing

• 1 Thread processes writes in serial order for 1 client socket

Review

This processing works and does not harm anything.

Problem(s)

• Non blocking write() (how currently implemented) can in very seldom (heavy network processing) cause partial data processing (returns the processed byte count) if the underlaying send-buffer has only limited space
• The current implementation takes only care of EAGAIN and not EWOULDBLOCK, both must be checked => bug 🐛!
• On partial write(), write() call has to be repeated (but how? man pages do not help), this has to be tested, i assume only a repeated write() call without data (similar to sendfile() call)

[clauspruefer]

See refactoring: an additional epoll() with EPOLLOUT in the servers refactored main incoming and outgoing process will do much better.