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.
Creates a new async handle. The handle is not active immediately. You have to use
This will increase the reference count of the async handle.
Main.run will wait until
send is called, if there are no other pendings tasks.
Wakeup the event loop and call the async handle's callback.
Warning: libuv will coalesce calls to
send, that is, not every call to it will yield an execution of the callback. For example: if
send is called 5 times in a row before the callback is called, the callback will only be called once. If
send is called again after the callback was called, it will be called again.