kkrpc

A TypeScript-first RPC library that enables seamless bi-directional communication between processes. Call remote functions as if they were local, with full TypeScript type safety and autocompletion support.

• JSR Package
• NPM Package
• Documentation by JSR
• Typedoc Documentation

Supported Environments

• stdio: RPC over stdio between any combinations of Node.js, Deno, Bun processes
• web: RPC over postMessage API and message channel between browser main thread and web workers, or main thread and iframe
  • Web Worker API (web standard) is also supported in Deno and Bun, the main thread can call functions in worker and vice versa.
• http: RPC over HTTP like tRPC
  • supports any HTTP server (e.g. hono, bun, nodejs http, express, fastify, deno, etc.)
• WebSocket: RPC over WebSocket

The core of kkrpc design is in RPCChannel and IoInterface.

• RPCChannel is the bidirectional RPC channel
• LocalAPI is the APIs to be exposed to the other side of the channel
• RemoteAPI is the APIs exposed by the other side of the channel, and callable on the local side
• rpc.getAPI() returns an object that is RemoteAPI typed, and is callable on the local side like a normal local function call.
• IoInterface is the interface for implementing the IO for different environments. The implementations are called adapters.
  • For example, for a Node process to communicate with a Deno process, we need NodeIo and DenoIo adapters which implements IoInterface. They share the same stdio pipe (stdin/stdout).
  • In web, we have WorkerChildIO and WorkerParentIO adapters for web worker, IframeParentIO and IframeChildIO adapters for iframe.

In browser, import from kkrpc/browser instead of kkrpc, Deno adapter uses node:buffer which doesn't work in browser.

interface IoInterface {
	name: string
	read(): Promise<Buffer | Uint8Array | string | null> // Reads input
	write(data: string): Promise<void> // Writes output
}

class RPCChannel<
	LocalAPI extends Record<string, any>,
	RemoteAPI extends Record<string, any>,
	Io extends IoInterface = IoInterface
> {}
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Examplesr

Below are simple examples.

Stdio Example

import { NodeIo, RPCChannel } from "kkrpc"
import { apiMethods } from "./api.ts"

const stdio = new NodeIo(process.stdin, process.stdout)
const child = new RPCChannel(stdio, { expose: apiMethods })
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import { spawn } from "child_process"

const worker = spawn("bun", ["scripts/node-api.ts"])
const io = new NodeIo(worker.stdout, worker.stdin)
const parent = new RPCChannel<{}, API>(io)
const api = parent.getAPI()

expect(await api.add(1, 2)).toBe(3)
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Web Worker Example

import { RPCChannel, WorkerChildIO, type DestroyableIoInterface } from "kkrpc"

const worker = new Worker(new URL("./scripts/worker.ts", import.meta.url).href, { type: "module" })
const io = new WorkerChildIO(worker)
const rpc = new RPCChannel<API, API, DestroyableIoInterface>(io, { expose: apiMethods })
const api = rpc.getAPI()

expect(await api.add(1, 2)).toBe(3)
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import { RPCChannel, WorkerParentIO, type DestroyableIoInterface } from "kkrpc"

const io: DestroyableIoInterface = new WorkerChildIO()
const rpc = new RPCChannel<API, API, DestroyableIoInterface>(io, { expose: apiMethods })
const api = rpc.getAPI()

const sum = await api.add(1, 2)
expect(sum).toBe(3)
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HTTP Example

Codesandbox: https://codesandbox.io/p/live/4a349334-0b04-4352-89f9-cf1955553ae7

api.ts

Define API type and implementation.

export type API = {
	echo: (message: string) => Promise<string>
	add: (a: number, b: number) => Promise<number>
}

export const api: API = {
	echo: (message) => {
		return Promise.resolve(message)
	},
	add: (a, b) => {
		return Promise.resolve(a + b)
	}
}
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server.ts

Server only requires a one-time setup, then it won't need to be touched again. All the API implementation is in api.ts.

import { HTTPServerIO, RPCChannel } from "kkrpc"
import { api, type API } from "./api"

const serverIO = new HTTPServerIO()
const serverRPC = new RPCChannel<API, API>(serverIO, { expose: api })

const server = Bun.serve({
	port: 3000,
	async fetch(req) {
		const url = new URL(req.url)
		if (url.pathname === "/rpc") {
			const res = await serverIO.handleRequest(await req.text())
			return new Response(res, {
				headers: { "Content-Type": "application/json" }
			})
		}
		return new Response("Not found", { status: 404 })
	}
})
console.log(`Start server on port: ${server.port}`)
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client.ts

import { HTTPClientIO, RPCChannel } from "kkrpc"
import { api, type API } from "./api"

const clientIO = new HTTPClientIO({
	url: "http://localhost:3000/rpc"
})
const clientRPC = new RPCChannel<{}, API>(clientIO, { expose: api })
const clientAPI = clientRPC.getAPI()

const echoResponse = await clientAPI.echo("hello")
console.log("echoResponse", echoResponse)

const sum = await clientAPI.add(2, 3)
console.log("Sum: ", sum)
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