The failing test has a temporal post condition which may not hold true on a heavily loaded system.

    public void testTimedAccept7() throws IOException {
        try (ServerSocket ss = boundServerSocket()) {
            ss.setSoTimeout(30*1000);
            long delay = 2000;
            scheduleClose(ss, delay);
            long startMillis = millisTime();
            try {
                ss.accept().close();
                fail();
            } catch (SocketException expected) {
                checkDuration(startMillis, delay-100, delay+2000);
            }
        }
    }

It possible that the scheduled close my not be delivery in timely manner, such that the temporal constraint on the epoch for delivery is somewhat contrived.

The main semantics that is extracted from the test is that the close is delivered prior the timeout set on the serversocket.