Protocol

The API is based on JSON RPC of WebSocket protocol. Repeated subscriptions will be canceled for the same data type.

A rpc call is represented by sending a Request object to a Server. The Request object has the following members:

jsonrpc

A String specifying the version of the JSON-RPC protocol. MUST be exactly "2.0".

method

A String containing the name of the method to be invoked.

params

A Structured value that holds the parameter values to be used during the invocation of the method. This member MAY be omitted.

ID

An identifier established by the Client that MUST contain a String, Number, or NULL value if included. If it is not included it is assumed to be a notification. The value SHOULD normally not be Null [1] and Numbers SHOULD NOT contain fractional parts [2]

The Server MUST reply with the same value in the Response object if included. This member is used to correlate the context between the two objects.

[1] The use of Null as a value for the id member in a Request object is discouraged, because this specification uses a value of Null for Responses with an unknown id. Also, because JSON-RPC 1.0 uses an id value of Null for Notifications this could cause confusion in handling.

[2] Fractional parts may be problematic, since many decimal fractions cannot be represented exactly as binary fractions.

1.1 Notification

A Notification is a Request object without an "id" member. A Request object that is a Notification signifies the Client's lack of interest in the corresponding Response object, and as such no Response object needs to be returned to the client. The Server MUST NOT reply to a Notification, including those that are within a batch request.

Notifications are not confirmable by definition, since they do not have a Response object to be returned. As such, the Client would not be aware of any errors (like e.g. "Invalid params","Internal error").

1.2 Parameter Structures

If present, parameters for the rpc call MUST be provided as a Structured value. Either by-position through an Array or by-name through an Object.

• by-position: params MUST be an Array, containing the values in the Server expected order.

• by-name: params MUST be an Object, with member names that match the Server expected parameter names. The absence of expected names MAY result in an error being generated. The names MUST match exactly, including case, to the method's expected parameters.

When a rpc call is made, the Server MUST reply with a Response, except for in the case of Notifications. The Response is expressed as a single JSON Object, with the following members:

jsonrpc

A String specifying the version of the JSON-RPC protocol. MUST be exactly "2.0".

result

This member is REQUIRED on success.

This member MUST NOT exist if there was an error invoking the method.

The value of this member is determined by the method invoked on the Server.

error

This member is REQUIRED on error.

This member MUST NOT exist if there was no error triggered during invocation.

The value for this member MUST be an Object as defined in section 4.1.

id

This member is REQUIRED.

It MUST be the same as the value of the id member in the Request Object.

If there was an error in detecting the id in the Request object (e.g. Parse error/Invalid Request), it MUST be Null.

Either the result member or error member MUST be included, but both members MUST NOT be included.

2.1 Error object

When a rpc call encounters an error, the Response Object MUST contain the error member with a value that is a Object with the following members:

code

A Number that indicates the error type that occurred.

This MUST be an integer.

message

A String providing a short description of the error.

The message SHOULD be limited to a concise single sentence.

data

A Primitive or Structured value that contains additional information about the error.

This may be omitted.

The value of this member is defined by the Server (e.g. detailed error information, nested errors etc.).

The error codes from and including -32768 to -32000 are reserved for pre-defined errors. Any code within this range, but not defined explicitly below is reserved for future use.

code	message	meaning
-32700	Parse error	Invalid JSON was received by the server. An error occurred on the server while parsing the JSON text.
-32600	Invalid Request	The JSON sent is not a valid Request object.
-32601	Method not found	The method does not exist / is not available.
-32602	Invalid params	Invalid method parameter(s).
-32603	Internal error	Internal JSON-RPC error.
-32000 to -32099	Server error	Reserved for implementation-defined server-errors.