Handles are closed automatically, if they are not longer referenced from the OCaml heap. Nevertheless, you should nearly always close them with
- if they wrap a file descriptor, you will sooner or later run out of file descriptors. The OCaml garbage collector doesn't give any guarantee, when orphaned memory blocks are removed.
- you might have registered some repeatedly called action (e.g. timeout, read_start,...), that prevent that all references get removed from the OCaml heap.
However, it's safe to write code in this manner:
let s = Uwt.Tcp.init () in let c = Uwt.Tcp.init () in Uwt.Tcp.nodelay s false; Uwt.Tcp.simultaneous_accepts true; if foobar () then (* no file descriptor yet assigned, no need to worry about exceptions inside foobar,... *) Lwt.return_unit (* no need to close *) else ...
If you want - for whatever reason - keep a file descriptor open for the whole lifetime of your process, remember to keep a reference to its handle.
val close_noerr : t -> unit
close_wait is only useful, if you intend to wait until all concurrent write and read threads related to this handle are canceled.
val is_active : t -> bool
Returns non-zero if the handle is active, zero if it's inactive. What "active" means depends on the type of handle:
Async.thandle is always active and cannot be deactivated, except by closing it with uv_close().
Udp.t, etc. handle - basically any handle that deals with i/o - is active when it is doing something that involves i/o, like reading, writing, connecting, accepting new connections, etc.
Rule of thumb: if a handle of type
Uwt.Foo.t has a uv_foo_start() function, then it's active from the moment that function is called. Likewise, uv_foo_stop() deactivates the handle again.
val ref' : t -> unit
Reference the given handle. References are idempotent, that is, if a handle is already referenced calling this function again will have no effect.
val unref : t -> unit
Un-reference the given handle. References are idempotent, that is, if a handle is not referenced calling this function again will have no effect.
val has_ref : t -> bool
Returns non-zero if the handle is referenced, zero otherwise.
val sleep : int -> unit Lwt.t
sleep d is a thread that remains suspended for
d milliseconds and then terminates.
Timers, that are executed only once (repeat=0), are automatically closed. After their callback have been executed, their handles are invalid. Call
close to stop a repeating timer