package uwt

Handles are closed automatically, if they are not longer referenced from the OCaml heap. Nevertheless, you should nearly always close them with close, because:

• 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.

Prefer close or close_noerr to close_wait. close or close_noerr return immediately (there are no useful error messages, beside perhaps a notice, that you've already closed that handle).

close_wait is only useful, if you intend to wait until all concurrent write and read threads related to this handle are canceled.