Protocol
This protocol draws inspiration from the JSON-RPC specification, encoded in a binary format.
Currently, the browser initiates communication with the server via
WebSocket using the specified
subprotocol "websocket.io-rpc-v0.1".
Frame
Each frame begins with an opcode (u8), indicating the frame type.
| Op Code (u8) | Frame Type | Description |
|---|---|---|
| 1 | Notify | Sent by the client or server to indicate an event with no Response expected. |
| 2 | Request | Sent only by the client to initiate an RPC call and expect a Response. |
| 3 | Reset | Sent only by the client to cancel an ongoing RPC call. |
| 4 | Response | Sent only by the server to return the result of a Request. |
Notify Frame
A Notify is a Request frame without an id field. A Request frame that is
a Notify signifies the Client's lack of interest in the corresponding
Response frame, and as such no Response frame needs to be returned to the
client. The Server MUST NOT reply to a Notify.
| Notify Frame | Type |
|---|---|
| Op Code | 1 (u8) |
| Event Name Size | u8 |
| Event Name | UTF8 |
| Payload | &[u8] |
- Event Name Size: The length of the event name, represented as
u8. So maximum event name (utf8 encoded) length is 255 bytes. - Event Name: A String (UTF8 encoded) containing the name of the method to be invoked.
- Payload: Application encoded data in bytes.
Request Frame
A rpc call is represented by sending a Call Frame to a Server.
| Call Frame | Type |
|---|---|
| Op Code | 2 (u8) |
| ID | u32 |
| Event Name Size | u8 |
| Event Name | UTF8 |
| Payload | &[u8] |
- ID: A unique identifier for the RPC call, encoded in big-endian byte order.
The remaining fields are encoded in the same manner as Notify frame.
Reset Frame
The Reset Frame is used to terminate the processing of an ongoing RPC call,
such as in the case of a timeout. If the server has already processed the RPC
call, the Reset frame has no effect.
| Reset Frame | Type |
|---|---|
| Op Code | 3 (u8) |
| ID | u32 |
- ID: The unique identifier (encoded in big endian byte order) of the RPC call to cancel.
Response Frame
When a rpc call is made, the Server MUST reply with a Response, except for in
the case of Notify.
| Response Frame | Type |
|---|---|
| Op Code | 4 (u8) |
| ID | u32 |
| Payload | &[u8] |
- ID: A unique identifier (
u32), encoded in big endian byte order. It MUST be the same as the value of theidfield in theRequestframe. - Payload: Application encoded data in bytes.