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From: Andreas Leitgeb <avl@logic.at>
Newsgroups: comp.lang.java.programmer
Subject: Re: server-side Socket does not recognize broken connection.
Date: Wed, 29 May 2019 14:50:14 -0000 (UTC)
Organization: A noiseless patient Spider
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Joerg Meier <joergmmeier@arcor.de> wrote:
> On Wed, 29 May 2019 11:03:18 -0000 (UTC), Andreas Leitgeb wrote:
>> PS: The real code does more interesting stuff while no input is available,
>> so it cannot wait blockingly.  The real code also has other exits from the
>> loop (based on input received), but that's not relevant for this SSCCE.
> In addition to Erics excellent answer,

Thanks also to Eric!

> I would like to add that I'm pretty
> certain that you can not write code like that without resorting to
> blocking.

Watching the Java server with strace (on linux), I see that Java calls
the system:
  ioctl(6, FIONREAD, [0])     = 0

Now I'm going to read up on why this syscall wouldn't report a broken socket,
and what other syscall (short of actually reading and risking to block)
would allow me to tell idle from broken.

Calling "lsof" on the Java process' pid shows that the OS does know the
socket is broken:
java    29340  avl    6u  IPv6          113368285       0t0       TCP
   localhost:65432->localhost:58500 (CLOSE_WAIT)

> You may want to look at NIO or higher level frameworks if you can
> not astract the blocking aspect away on your own for some reason.

A separate thread to read blockingly and shovel the results into a 
Queue (as Eric suggested) is plausible, assuming that it works. 
Trying to replace inputStreams by nio is also on my "TO CHECK" list.

Thanks anyway for pointing me in the direction that available() alone
just isn't designed to recognize broken sockets.

I consider my question answered. Thanks!