# ProtocolClient

> Documentation for Redweb 0.13.3. Install that exact version when following these examples.

Dependency-free helper from redweb/client for opt-in versioned routes. It builds, sends, and validates stable envelopes from the same checked-in schema used by server constants and TypeScript declarations.

## Explain it like I’m five

ProtocolClient is a phrasebook shared with the browser. It puts outgoing messages into Redweb’s expected envelope and checks incoming envelopes before your code trusts them.

## When should I use it?

Use it for opt-in versioned routes when browser clients should share protocol constants, parsing, sequencing, and error handling with the server.

## Follow the example

This API pattern illustrates the named surface; it may require application-owned classes, credentials, or assets. Start from a complete recipe for a runnable application.

```js
const { ProtocolClient, ERROR_CODES } = require('redweb/client')

const socket = new WebSocket('wss://game.example/match?redwebVersion=1')
const client = new ProtocolClient(socket, '1')
client.send('move', { x: 4, y: 2 }, { sequence: 17 })
```

1. The client connects to the versioned route and creates a ProtocolClient for that version.
2. send builds a stable typed envelope containing payload and optional sequence metadata.
3. parse validates server messages so application code can respond to known errors such as rate limiting.

## Methods and members

### constructor(socket, version)

Wraps any socket-like object with send(data) and selects the envelope version.

### envelope(type, payload, metadata?)

Builds a stable versioned event with optional requestId and sequence.

### send(type, payload, metadata?)

Serializes and sends one versioned event through the wrapped socket.

### parse(value)

Parses and validates a protocol event or error envelope.

## What should I watch for?

Protocol validation is not domain validation. Continue checking payload shape, authorization, and game rules on the authoritative server.