pear-docs/guide/making-a-pear-terminal-app.md

Making a Pear Terminal Application

This guide demonstrates how to build a peer-to-peer chat application.

It continues where Starting a Pear Terminal Project left off.

{% embed url="https://www.youtube.com/watch?v=UoGJ7PtAwtI" %} Build with Pear - Episode 04: Pear Terminal Applications {% embeded %}

Step 1. Install modules

For the chat part of the app, the same modules are needed as in Making a Pear Desktop Application, hyperswarm, b4a and hypercore-crypto.

Pear runs on Bare, a lightweight JavaScript runtime which is similar to Node.js but comes with very few internal modules. Almost all Bare functionality comes from dependencies. Pear Terminal Applications are Bare applications so we will need bare-readline and bare-tty to read user input.

npm i bare-readline bare-tty hyperswarm b4a hypercore-crypto

Step 2. JavaScript

Replace index.js with

import Hyperswarm from 'hyperswarm'
import b4a from 'b4a'
import crypto from 'hypercore-crypto'
import readline from 'bare-readline'
import tty from 'bare-tty'

const { teardown, config } = Pear
const key = config.args.pop()
const shouldCreateSwarm = !key
const swarm = new Hyperswarm()
const log = console.log
const rl = readline.createInterface({
  input: new tty.ReadStream(0),
  output: new tty.WriteStream(1)
})

swarm.on('connection', peer => {
  const name = b4a.toString(peer.remotePublicKey, 'hex').substr(0, 6)
  console.log(`[info] New peer joined, ${name}`)
  peer.on('data', message => appendMessage({ name, message }))
})
swarm.on('update', () => {
  console.log(`[info] Number of connections is now ${swarm.connections.size}`)
})

if (shouldCreateSwarm) {
  await createChatRoom()
} else {
  await joinChatRoom(key)
}

rl.input.setMode(tty.constants.MODE_RAW)
rl.on('data', line => {
  sendMessage(line)
  rl.prompt()
})
rl.prompt()

async function createChatRoom () {
  const topicBuffer = crypto.randomBytes(32)
  await joinSwarm(topicBuffer)
  const topic = b4a.toString(topicBuffer, 'hex')
  console.log(`[info] Created new chat room: ${topic}`)
}

async function joinChatRoom (topicStr) {
  const topicBuffer = b4a.from(topicStr, 'hex')
  await joinSwarm(topicBuffer)
  console.log(`[info] Joined chat room`)
}

async function joinSwarm (topicBuffer) {
  const discovery = swarm.join(topicBuffer, { client: true, server: true })
  await discovery.flushed()
}

function sendMessage (message) {
  const peers = [...swarm.connections]
  for (const peer of peers) peer.write(message)
}

function appendMessage ({ name, message }) {
  console.log(`[${name}] ${message}`)
}

Step 3. Run in dev mode

To test this chat app, in one terminal run pear dev ..

The app will output something similar to:

[info] Created new chat room: a1b2c35fbeb452bc900c5a1c00306e52319a3159317312f54fe5a246d634f51a

In another terminal use this key as input, pear dev . a1b2c35fbeb452bc900c5a1c00306e52319a3159317312f54fe5a246d634f51a.

The app will output:

[info] Number of connections is now 0
[info] New peer joined, 6193ec
[info] Number of connections is now 1
[info] Joined chat room

Type something in one of the applications. Two Terminal Applications are now connected peer-to-peer.

Next

• Sharing a Pear Application