String contentKey = NetworkTestUtil.randomString();
// create a message with target node B
TestDirectMessageWithReplyMaxSending message = new TestDirectMessageWithReplyMaxSending(nodeB
.getConnection().getPeer().getPeerAddress(), contentKey);
// create and add a callback handler
TestCallBackHandlerMaxSendig callBackHandler = message.new TestCallBackHandlerMaxSendig(nodeA);
message.setCallBackHandler(callBackHandler);
// send message
assertTrue(nodeA.getMessageManager().sendDirect(message, getPublicKey(nodeB)));