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.

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
> {}

Examples

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 });

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);

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);

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);

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);
  },
};

`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}`);

`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);

Chrome Extension Example

`background.ts`

import { ChromeBackgroundIO, RPCChannel } from "kkrpc";
import type { API } from "./api";
 
// Store RPC channels for each tab
const rpcChannels = new Map<number, RPCChannel<API, {}>>();
 
// Listen for tab connections
chrome.runtime.onConnect.addListener((port) => {
  if (port.sender?.tab?.id) {
    const tabId = port.sender.tab.id;
    const io = new ChromeBackgroundIO(tabId);
    const rpc = new RPCChannel(io, { expose: backgroundAPI });
    rpcChannels.set(tabId, rpc);
 
    port.onDisconnect.addListener(() => {
      rpcChannels.delete(tabId);
    });
  }
});

`content.ts`

import { ChromeContentIO, RPCChannel } from "kkrpc";
import type { API } from "./api";
 
const io = new ChromeContentIO();
const rpc = new RPCChannel<API, API>(io, {
  expose: {
    updateUI: async (data) => {
      document.body.innerHTML = data.message;
      return true;
    },
  },
});
 
// Get API from background script
const api = rpc.getAPI();
const data = await api.getData();
console.log(data); // { message: "Hello from background!" }

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