# Does the IPC protocol allow for double communication between two apps?

**URL:** <https://forum.legato.io/t/does-the-ipc-protocol-allow-for-double-communication-between-two-apps/5750>\
**Category:** Uncategorized\
**Created:** [May 11, 2021, 2:12pm UTC](https://forum.legato.io/t/does-the-ipc-protocol-allow-for-double-communication-between-two-apps/5750 "2021-05-11T14:12:16Z")\
**Posts on this page:** 1\
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**Author:** ![jyijyi](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.legato.io/jyijyi/32/822_2.png) [@jyijyi](https://forum.legato.io/u/jyijyi)\
**Post date:** [May 11, 2021, 3:02pm UTC](https://forum.legato.io/t/does-the-ipc-protocol-allow-for-double-communication-between-two-apps/5750/2 "2021-05-11T15:02:25Z")

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You can see this, we can register a callback for a server to call client:

> [@Cannot get callback between components (IPC) to work properly](https://forum.legato.io/t/cannot-get-callback-between-components-ipc-to-work-properly/4653/3):
>
> Thanks for the response [jyijyi](https://forum.legato.io/u/jyijyi)! I got the callback working based on your application. The reference code (as seen [here](https://docs.legato.io/latest/c_eventLoop.html#c_event_layeredPublishSubscribe)) is not correct, the following line: tempSensor\_ChangeHandlerRef\_t clientHandlerFunc = secondLayerHandlerFunc; has to be: tempSensor\_ChangeHandlerFunc\_t clientHandlerFunc = secondLayerHandlerFunc; Thanks again slight_smile

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