Make all events happens in single thread to avoid class status error.
Trigger some events in new thread rather than processor thread.
Fix bug of cancel receiving file function.
Add checking logic for socketChannel status.
Fix bug of isClosed method of NioSessionProcessor.
Optimize memory-mapping file receiving process.
Remove unnecessary log output.
Optimize file transfer performance.
针对服务器连接新增了两个方法
Merge branch 'master' into lyj