Remoboard (Swift)

Remoboard (远程输入法) lets you type in your computer's browser and have the text appear instantly on your phone, inside whatever app you're using. The phone runs a custom keyboard extension that hosts a tiny web server; you open the URL it shows, enter a pairing PIN, and start typing.

This is a ground-up Swift rewrite of the original Objective-C/C++ app. The legacy sources are preserved under ObjcVersion/ for reference.

What changed from the Objective-C version

• No C++ / Boost / mongoose. The HTTP + WebSocket relay is ~600 lines of Swift built on raw POSIX sockets and a single poll() loop (RemoboardKit/Sources/RemoServer.swift). Raw sockets are used deliberately — Network.framework's NWListener triggers the iOS local-network permission prompt, which can't be granted from a keyboard extension. This deletes the entire vendored boost_1_70_0 tree (~63k files).
• Versioned JSON protocol over WebSocket, replacing the command##rkb-…##content string separator. See RemoboardKit/Sources/Protocol.swift.
• PIN pairing. The keyboard shows a 6-digit PIN (stable for the session); a client must send it before any input is honored, and the server drops a connection after 5 wrong attempts, so a random person on the same Wi-Fi can't type into your phone.
• Rebuilt web UI (Svelte, single offline file): proper CJK/IME handling via composition events, live mirror of the phone's text field, robust exponential-backoff reconnect + heartbeat, quick-word management, clipboard, send history, light/dark (follows the system) and a responsive, mobile-friendly layout.
• Localized into 10 languages (English, 简体中文, 日本語, 한국어, Deutsch, Français, Español, Português, Русский, Italiano) across the web UI, host app, and keyboard.
• SwiftUI host app and a Swift/UIKit keyboard extension.
• Remote clipboard — push text to / pull text from the phone's system clipboard from the browser.
• Handoff — hand the connection URL to the host app, which publishes an Apple Continuity activity so you can resume on your Mac via Handoff.
• Bluetooth / legacy IP modes dropped.

Layout

RemoboardKit/        Shared framework (app + extension)
  Sources/
    Protocol.swift       JSON wire protocol + codec
    Settings.swift       App-group settings (quick words, etc.)
    LocalAddresses.swift IPv4 interface enumeration
    WebSocket.swift      RFC 6455 handshake + frame codec
    RemoServer.swift     POSIX-socket HTTP/WebSocket server + pairing
    SiteResources.swift  Loads the bundled web UI
  Resources/site/      Built web UI (index.html, favicon.ico)
keyboard/            RemoKeyboard extension (UIKit)
remoboard/           Host app (SwiftUI)
web/                 Svelte source for the browser UI
project.yml          XcodeGen project definition
ObjcVersion/         Original Objective-C/C++ app (archived)

Building

Prerequisites: Xcode 15+, XcodeGen (brew install xcodegen), Node 18+ (only to rebuild the web UI).

# 1. (only if you changed web/) rebuild the browser UI into the framework bundle
cd web && npm install && npm run deploy && cd ..

# 2. generate the Xcode project from project.yml
xcodegen generate

# 3. open and run on a real device (keyboard extensions are limited in the simulator)
open Remoboard.xcworkspace 2>/dev/null || open Remoboard.xcodeproj

Command-line build check (simulator, no signing):

xcodebuild -project Remoboard.xcodeproj -scheme Remoboard \
  -sdk iphonesimulator -destination 'generic/platform=iOS Simulator' \
  CODE_SIGNING_ALLOWED=NO build

On device: enable Remoboard in Settings → General → Keyboard → Keyboards, turn on Allow Full Access, switch to the Remoboard keyboard, then open the shown http://<phone-ip>:7777 URL on your computer and enter the PIN.

Protocol (v1)

Client → phone: {"v":1,"t":"hello","pin":"482103"}, {"t":"input","text":"…","seq":7}, {"t":"delete","seq":8}, {"t":"move","dir":"left","seq":9}, {"t":"clip-set","text":"…"}, {"t":"clip-get"}, {"t":"handoff","text":"…"}, {"t":"ping"}.

Phone → client: {"t":"paired"}, {"t":"deny","reason":"pin"}, {"t":"context","before":"…","after":"…"}, {"t":"quickwords","items":[…]}, {"t":"clip","text":"…"}, {"t":"info","message":"…"}, {"t":"pong"}.

Developer packages

Client libraries that drive the keyboard from code (see packages/). All published and speak the same WebSocket protocol:

Package	Install	Docs
remoboard (Node.js)	npm install remoboard	packages/node
remoboard (Python)	pip install remoboard	packages/python
remoboard-mcp (MCP server)	npx -y remoboard-mcp	packages/mcp

// Node
import { RemoboardClient } from 'remoboard'
const rb = new RemoboardClient({ host: '192.168.1.20', pin: '482103' })
await rb.connect()
await rb.type('Hello 世界 👋')
await rb.enter()

# Python
from remoboard import RemoboardSync
with RemoboardSync(host='192.168.1.20', pin='482103') as rb:
    rb.type('Hello 世界 👋')
    rb.enter()

The MCP server lets an AI assistant (Claude, …) type into your phone — add it with npx -y remoboard-mcp and REMOBOARD_HOST / REMOBOARD_PIN; see packages/mcp.

License

MIT. See LICENSE.