Revision 02e7f855cb4dcc54e2f1e1de41e8720cd1a9ed7f authored by pecornilleau on 04 April 2024, 16:11:12 UTC, committed by pecornilleau on 04 April 2024, 17:15:54 UTC
1 parent eaf7214
port.ml
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(* The trick for generating a fresh port relies on a non-POSIX but
standard behavior implemented by many operating systems, including
Linux and macOS.
[Unix.bind] binds the address (IP with port) given in parameters to
the socket. If the port of the address given is [0], a fresh port
is used, then the operating system actually replace the port with a
fresh port which is known not used by the operating
system. Consequently, to generate a fresh port, we open a socket,
bind it to a fake address with port [0]. Ask for the address of the
socket and return the port given by the operating system. Finally,
we close the socket.
*)
let fresh () =
let dummy_socket = Unix.(socket PF_INET SOCK_STREAM 0) in
Fun.protect ~finally:(fun () -> Unix.close dummy_socket) @@ fun () ->
Unix.bind dummy_socket Unix.(ADDR_INET (inet_addr_loopback, 0)) ;
let addr = Unix.getsockname dummy_socket in
match addr with ADDR_INET (_, port) -> port | _ -> assert false
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