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<?xml-stylesheet type="text/xsl" href="https://devzone.nordicsemi.com/cfs-file/__key/system/syndication/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:wfw="http://wellformedweb.org/CommentAPI/" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>Why are most services&amp;#39;s evt_handler in peripheral example  NULL, but central&amp;#39;s ones aren&amp;#39;t?</title><link>https://devzone.nordicsemi.com/f/nordic-q-a/40968/why-are-most-services-s-evt_handler-in-peripheral-example-null-but-central-s-ones-aren-t</link><description>Hello~ 
 I have finished a few easy peripheral project. 
 Now I tried to understand the structure of central example, ex: ble_hrs_c, ble_nus_c.... 
 I found that services of peripheral wouldn&amp;#39;t be provided evt_handler, except ble_nus. 
 What is the time</description><dc:language>en-US</dc:language><generator>Telligent Community 13</generator><lastBuildDate>Thu, 29 Nov 2018 12:14:51 GMT</lastBuildDate><atom:link rel="self" type="application/rss+xml" href="https://devzone.nordicsemi.com/f/nordic-q-a/40968/why-are-most-services-s-evt_handler-in-peripheral-example-null-but-central-s-ones-aren-t" /><item><title>RE: Why are most services's evt_handler in peripheral example  NULL, but central's ones aren't?</title><link>https://devzone.nordicsemi.com/thread/159540?ContentTypeID=1</link><pubDate>Thu, 29 Nov 2018 12:14:51 GMT</pubDate><guid isPermaLink="false">137ad170-7792-4731-bb38-c0d22fbe4515:168b9db6-0f09-45a5-955f-f54afe6d2cf2</guid><dc:creator>Vidar Berg</dc:creator><description>&lt;p&gt;Hello,&lt;/p&gt;
&lt;p&gt;For the NUS the application needs an event handler to know when data&amp;nbsp;has been received from the&amp;nbsp;client unlike the hr service where the app is only sending data. But you can use the event from hr service&amp;nbsp; if you want you app to get notified when the client has enabled or disabled notification. In other words, event handlers are optional as long required events are handled internally inside the service module. You can see what kind of events the event handler will notify the app about if you search for &amp;quot;evt_handler&amp;quot; inside the service module.&amp;nbsp;&lt;/p&gt;
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