code: @Test public void testHeartbeat() throws Exception {
    URL serverURL=URL.valueOf("header://localhost:55555?transporter=netty3");
    serverURL=serverURL.addParameter(Constants.HEARTBEAT_KEY,1000);
    TestHeartbeatHandler handler=new TestHeartbeatHandler();
    server=Exchangers.bind(serverURL,handler);
    System.out.println("Server bind successfully");
    client=Exchangers.connect(serverURL);
    Thread.sleep(10000);
    System.err.println("++++++++++++++ disconnect count " + handler.disconnectCount);
    System.err.println("++++++++++++++ connect count " + handler.connectCount);
    Assert.assertTrue(handler.disconnectCount == 0);
    Assert.assertTrue(handler.connectCount == 1);
  }
  