# RPC Call Reply

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Sends response to the RPC Call originator. All incoming RPC requests are passed through Rule Chain as Messages. Also all RPC requests have request ID field. It is used for mapping requests and responses. Message Originator must be a **Device** entity because RPC response is initiated to the Message Originator.

Node configuration has special request ID field mapping. If the mapping is not specified, **requestId** metadata field is used by default.

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RPC request can be received via different transports:

* MQTT
* HTTP
* CoAP

Message will be routed via **Failure** chain in the following cases:

* Inbound Message originator is not a **Device** entity
* Request id is not present in the Message metadata
* Inbound Message payload is empty