BaseHandler

Documentation for Redweb 0.13.2. Install that exact version when following these examples.

Abstract message handler. Provide a name in the constructor; clients send { type: name, ... } to target JSON messages, while binary frames can be accepted and handled as raw Buffer payloads.

Explain it like I’m five

BaseHandler is a labeled mailbox. A message with the matching type goes directly into that mailbox, so your code does not need a switch statement.

When should I use it?

Create a small handler for each message type that deserves its own validation, authorization, rate policy, and behavior.

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.

const { BaseHandler } = require('redweb')

class UploadHandler extends BaseHandler {
  constructor() { super('upload') }

  onMessage(socket, message) {
    socket.sendJson({ type: 'upload:control', action: message.action })
  }

  acceptsBinary(socket, buffer) {
    return buffer.length > 0
  }

  onBinaryMessage(socket, buffer) {
    socket.sendJson({ type: 'upload:chunk', bytes: buffer.length })
  }
}

1. The handler name declares the message type it accepts.
2. SocketRoute performs dispatch before onMessage runs.
3. The handler validates the payload, changes authoritative state, and sends or broadcasts the result.

Methods and members

constructor(name)

Stores the handler name used by incoming messages.

handleMessage(socket, message)

Calls onMessage; override only if you need pre/post handling logic.

onMessage(socket, message)

Required; implement your message processing here. Throwing will close the socket with an error.

acceptsBinary(socket, buffer)

Optional selector used by SocketRoute to choose a handler for binary frames. Return true when this handler should receive the Buffer.

handleBinaryMessage(socket, buffer)

Calls onBinaryMessage. If onBinaryMessage is not implemented, Redweb sends a "Binary messages are not supported by this handler" error.

onBinaryMessage(socket, buffer)

Optional; override for normal binary-message handling. The second argument is the raw Buffer payload.

onInitialContact(socket)

Optional hook for first-touch logic (not used by default route).

What should I watch for?

Do not add a second message.action dispatcher inside one handler. That hides protocol operations and defeats type-based routing.