nm.setContent(new StringSource("<request>" + i + "</request>"));
me.setInMessage(nm);
Thread t = new ProviderThread(i, channel);
t.start();
long before = System.currentTimeMillis();
channel.sendSync(me, 5000);
long after = System.currentTimeMillis();
if (i % 2 == 1) {
// throttle sleep 4000ms for every 2 message, so
// the duration should > 4000ms
assertTrue(after - before > 4000);