What's MessageTypeId in OCPP request payload

May 24, 2022

In OCPP 1.6, the client (Charging Station) sends a CALL (similar to request in HTTP) to server (Charging Station Management Systems). All CALLs have a strict structure of 4 elements:

MessageTypeId (integer)
UniqueId (UUID, string)
Action (string)
Payload (JSON object containing the arguments relevant to the
Action.)

I have gone through the documentation but I cannot find MessageTypeId. So I want to know whether it is just a random number?

Example request payload:

[
  2,// <----- I want to know, where I can find this. 
  "a7caa7a1-c309-43bd-af3f-b5c1c4f9657e", 
  "Authorize",
  {
    "idTag": "${req.body.idTag}"
  }
]

>Solution :

MessageTypeId Defines the type of Message, whether it is Call, CallResult or CallError:

MessageType | MessageTypeId | Direction

CALL        |       2       | Client-to-Server

CALLRESULT  |       3       | Server-to-Client

CALLERROR   |       4       | Server-to-Client

You can read more on page 9 of This document .