wss-rpc2

WebSocket Server and Client implementation of the JSON RPC2 spec.
Powered by ws.

Basic functionality, according to the spec:

• Method call: client -> server (request/response)
• Notifications: client -> server (notification)

Extended functionality:

• Events: server -> client (to all / to some / to a single client)
• Reconnect and keep alive
• Stateful client connection
• The client works in both node and browser

Quick start

Installation:

npm i wss-rpc2

Backend / Server:

import { RPCServer, RPCEvent } from 'wss-rpc2'

const server = new RPCServer({ port: 3000 })

server.registerMethod('multiply', (params) => {
  return params[0] * params[1]
})

Frontend / Client:

import { RPCClient } from 'wss-rpc2'

const client = new RPCClient('ws://localhost:3000')
const result = await client.call('multiply', [3, 5])

See more examples.

RPCServer API

new RPCServer(options: IRPCServerOptions)

Parameters:

• options: IRPCServerOptions<State = any> extends ServerOptions
  • wss?: ws.WebSocketServer - existing WebSocketServer (ws) instance
  • keepAlive?: number - ping clients every N ms (default: 300000 // 5 min)
  • stateFactory?: () => State - initial state factory of the connected client
  • ...ServerOptions (see ws library)

---

RPCServer.registerMethod(name: string, method: IRPCMethod): void

Parameters:

• name: string - name of the RPC method
• method: IRPCMethod - RPC method function, see types

---

RPCServer.callMethod(name: string, params: IRPCParams): Promise<any>

Call a method explicitly

Parameters:

• name: string - name of the RPC method
• params: IRPCParams - params of the RPC method

---

RPCServer.getConnections(): RPCConnection[]

Returns active connection instances.

---

RPCServer.close(): Promise

Closes all active client's connections and stops the server.

---

RPCServer.on(eventName: string, listener: Function, once?: boolean): Function

Subscribe a listener to the event. Returns unsubscribe function.

RPCServer Events:

• listening (params: empty) - on server start
• connect (params: RPCConnection) - on client connect
• disconnect (params: RPCConnection) - on client disconnect
• request (params: RPCRequest) - on after request received
• response (params: RPCResponse) - on before response sent
• error (params: Error | unknown) - on server error
• close (params: empty) - on server stop

RPCClient API

new RPCClient(address: string, options?: IRPCClientOptions)

Parameters:

• address: string - URL of the RPCServer
• options: IRPCClientOptions
  • autoConnect?: boolean - if false, then use client.connect() (default: true)
  • reconnectIntervals?: number[] - reconnect intervals sequence. Example: [1000, 1500, 2000] will wait between reconnect: 1000ms, 1500ms, 2000ms, ..., 2000ms, until reconnectLimit is reached (default: [1000] - every 1000 ms)
  • reconnectLimit?: number - 0 - unlimited, -1 - disabled (default: 1000)
  • requestTimeout?: number - request timeout (default: 10000)

---

RPCClient.state: 'init' | 'connecting' | 'connected' | 'stopped'

Client connection state:

• init - before connect() has been called
• connecting - connection or reconnection is in process
• connected - active connection state
• stopped - if disconnect() has been called or reconnectLimit is reached

---

RPCClient.connected: Promise<void>

Connection promise. However, it is not necessary to wait for a connection, because requests will be queued up until the connection is established.

const client = new RPCClient()
await client.connected
// connected!

---

RPCClient.connect(): Promise<void>

Manual connect, if autoConnect = false

const client = new RPCClient({ autoConnect: false })
await client.connect()
// connected!

---

RPCClient.disconnect(): Promise<void>

Disconnects and stops a reconnect-observer.

---

RPCClient.call(method: string, params?: IRPCParams): Promise<RPCResponse>

Calls the method and waits for a response.

---

RPCClient.notify(method: string, params?: IRPCParams): void

Notifies the server without waiting for a response.

---

RPCClient.on(eventName: string, listener: Function, once?: boolean): Function

Subscribe a listener to the event. Returns unsubscribe function.

RPCClient Events:

• connect (params: empty) - on connect
• disconnect (params: empty) - on disconnect
• error (params: Error | unknown) - on error
• request (params: IRPCRequestObject) - on before request sent
• response (params: IRPCResponseObject) - on response received
• event (params: RPCEvent) - on server event received

RPCConnection <State = unknown> API

id: string

Connection identifier

---

ws: WebSocket

Browser WebSocket object (isomorphic-ws is used for the node client)

---

state?: State

Domain state of the connection, if defined by IRPCServerOptions.stateFactory (and State generic for TS).

---

lastActivity: number = 0

Last client's activity timestamp

---

RPCConnection.emit (event: RPCEvent, cb?: (e: Error) => void)

Emit an event to the client. Example:

const event = new RPCEvent({ event: 'hello', params: {} })
server.getConnections().forEach(connection => {
  connection.emit(event, e => console.error(e))
})

Types

interface IRPCServerOptions extends ws.ServerOptions {
  wss?: WebSocketServer
  keepAlive?: number
  stateFactory?: () => State
}

interface IRPCClientOptions {
  autoConnect?: boolean
  reconnectIntervals?: number[]
  reconnectLimit?: number
  requestTimeout?: number
}

type IRPCParams = { [key: string]: unknown } | unknown[]

type IRPCMethod<Req extends IRPCParams = any, Res = any, State = any>
        = (params: Req, connection: RPCConnection<State>) => Res

interface IRPCRequestObject {
  jsonrpc: '2.0'
  id?: string | number
  method: string
  params?: IRPCParams
}

interface IRPCResponseObject {
  jsonrpc: '2.0'
  id: string | number | null
  result?: any
  error?: IRPCError
}

interface IRPCError {
  code: number
  message: string
  data?: unknown
}

Typescript

Typescript support provides several useful features for typing request, responses and connection state.

import { RPCServer } from 'wss-rpc2'

const server = new RPCServer<IAppUserState>({
  stateFactory: () => ({ authorized: false })
})

server.registerMethod<IRpcLogin['request'], IRpcLogin['response']>('login', async (params, connection) => {
  const user = await auth(params)
  if (user) {
    connection.state.authorized = true
    connection.state.email = user.email
    connection.state.id = user.id
  }
  return user
})

interface IAppUserState {
  authorized: boolean
  email?: string
  id?: string
}

interface IRpcLogin {
  request: {
    login: string
    password: string
  }
  response: {
    user?: {
      id: string
      email: string
    }
  }
}

import { RPCClient } from 'wss-rpc2'

const client = new RPCClient(url)
const { error, result } = await client.call<{ user: IUser | null }>('login', { email, password })
console.log(result?.user?.id)

Examples

To be done
Also see tests