但是，如果不在该回调中编写要做某事的代码，则代码或应用程序客户机将得不到任何报告。
But if you don't write code to do something in that callback, nothing will get reported to your code or to the application client.
回调可为发布程序提供增强的功能性，这与我们的另一篇文章中所描述的客户机订阅类似。
Similar to the subscribing clients described in our other article, callbacks provide enhanced functionality for publishers.
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