PHP - Manual: EventListener (官方文档)
(PECL event >= 1.5.0)
Represents a connection listener.
$cb) : void
Numeric file descriptor of the underlying socket. (Added in event-1.6.0 .)
By default Libevent turns underlying file descriptors, or sockets, to non-blocking mode. This flag tells Libevent to leave them in blocking mode.
If this option is set, the connection listener closes its underlying socket when the EventListener object is freed.
If this option is set, the connection listener sets the close-on-exec
flag on the underlying listener socket. See platform documentation for
for more information.
By default on some platforms, once a listener socket is closed, no other socket can bind to the same port until a while has passed. Setting this option makes Libevent mark the socket as reusable, so that once it is closed, another socket can be opened to listen on the same port.
Allocate locks for the listener, so that it’s safe to use it from multiple threads.