# WebSocket Protobuf

Consume typed Polyester realtime channels with Protobuf payloads alongside ConnectRPC.

WebSocket Protobuf is the realtime companion for typed ConnectRPC and SDK integrations. It uses binary Protobuf payloads over WebSocket while ConnectRPC continues to handle request-response calls.

> **This is not ConnectRPC streaming**
>
> The payloads use Protobuf message types, but connection tokens, subscriptions, and reconnects follow the [WebSocket session model](https://testnet.polyester.com/docs/developer-docs/shared-concepts/websocket-session-model).

## When to use Protobuf channels

Choose WebSocket Protobuf when:

- you use an official SDK realtime client
- your application already uses generated Protobuf message types
- compact typed payloads matter more than direct inspection
- the required stream is available only as Protobuf

Encoding support is channel-specific. A Protobuf channel does not guarantee an equivalent JSON channel.

## Channel implementation

1. Choose a Protobuf channel

   Use the official SDK product method or identify the exact channel and published message type for a custom client.

2. Decode with generated types

   Decode each binary publication with the message type assigned to that channel. Apply the integer and identifier conventions defined by the field contract.

> **Protobuf is not SBE**
>
> Do not decode realtime Protobuf frames with the [SBE WebSocket](https://testnet.polyester.com/docs/developer-docs/sbe-websocket/getting-started) schema. SBE WebSocket is a separate binary order-entry session.