vscode-http-jsonrpc

NPM module to implement bidirectional communication between a jsonrpc client and server over HTTP + SSE.
Server can send request too.

Installation

pnpm add vscode-http-jsonrpc

Usage

This package is designed as a full-duplex transport: request/notification traffic flows over HTTP POST, while responses and server push messages flow over SSE.

Server (node.js)

import { Hono } from 'hono';
import { serve } from '@hono/node-server';
import { createHttpServerMessageConnection } from 'vscode-http-jsonrpc';

//rpcApp is a hono app
const { app: rpcApp, connection } = createHttpServerMessageConnection();
const app = new Hono()
app.route('/xxx', rpcApp);// or app.mount('/xxx',rpcApp.fetch)
serve({ fetch: app.fetch, port: 3000 });


connection.onRequest("ping", async () => {
  const result = await connection.sendRequest("ping")
  console.log(result)
  return "pong from server"
})
connection.listen();

Client (browser/node.js)

import { createHttpClientMessageConnection } from 'vscode-http-jsonrpc';

const connection = createHttpClientMessageConnection('http://localhost:3000/xxx/');
connection.onRequest('ping', () => 'pong from client');
connection.listen();

const result = await connection.sendRequest("ping")
console.log(result)

Notes

• Mount path: The client baseUrl must match where you mounted the RPC sub-app (e.g. http://localhost:3000/xxx or http://localhost:3000/xxx/). With or without a trailing slash is fine—the client normalizes the base URL before resolving rpc and sse endpoints.
• listen() once: Call connection.listen() exactly one time per MessageConnection. Calling it again throws Connection is already listening.
• Register handlers before listen(): You must register onRequest / onNotification before listen(). This ordering is required so every inbound request and notification from the peer is handled correctly; registering handlers afterward is unsafe.
• Full-duplex example: The ping snippet shows both sides issuing requests over the same connection.