On 5/08/2022 8:24 am, [email protected] wrote:
I suspect that this is the wrong list; please redirect me if so.
Redirected to net-dev
Cheers,
David
The docs for this method:
https://docs.oracle.com/en/java/javase/18/docs/api/java.base/java/net/InetAddress.html#getLocalHost()
<https://docs.oracle.com/en/java/javase/18/docs/api/java.base/java/net/InetAddress.html#getLocalHost()>
say that it “Returns the address of the local host. This is achieved by
retrieving the name of the host from the system, then resolving that
name into an InetAddress.”
This is true enough in simple cases, but horribly misleading in
non-trivial cases.
As far as I can tell it can’t return “the address” because the local
host may have multiple addresses.
Instead it returns “an address” of the local host. My laptop right now
has 3 addresses: IPv6 loopback, IPv4 from home WiFi, and IPv4 from
company network via VPN.
As far as I can tell (please correct me if I’m wrong!!) if there are
multiple addresses, the current implementation makes no effort to pick a
more “useful” one.
Instead, it takes whatever addresses it gets from the OS and returns the
first one.
Thus, in theory, and even in practice, it’s perfectly possible to get
into a situation where all of the following hold:
“It worked fine yesterday!”
“I didn’t change anything, honest!”
And yet, “nothing works today” (because, unbeknownst to mere mortals
like me, the OS happened to return things in a different order today.)
Again, please correct me if I’m wrong and there actually are some
guarantees, either by virtue of the spec, or by virtue of “it just so
happens that in practice you will tend to get XYZ”.
But if I’m right, then I suggest the following tweak to the documentation:
Returns the address of the local host. If the local host has multiple
addresses, an arbitrary one will be chosen and returned.
This is achieved by retrieving the name of the host from the system,
then resolving that name into a list of one or more `InetAddress`es and
then choosing an arbitrary address from that list.
(irrelevant but: really wish Javadoc had a lightweight notation for code
like markdown’s `code(blocks)`)
Just my two cents. Again, please redirect me if this is the wrong list,
and correct me if I’m wrong re: no guarantees about which address is
returned.
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