Code files

Chapter05/creating-an-smtp-server/smtp-server/index.js

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+'use strict'
+
+const fs = require('fs')
+const path = require('path')
+const smtp = require('smtp-protocol')
+const hosts = new Set(['localhost', 'example.com'])
+const users = new Set(['you', 'another'])
+const mailDir = path.join(__dirname, 'mail')
+
+function ensureDir (dir, cb) {
+  try { fs.mkdirSync(dir) } catch (e) {
+    if (e.code !== 'EEXIST') throw e
+  }
+}
+
+ensureDir(mailDir)
+for (let user of users) ensureDir(path.join(mailDir, user))
+
+const server = smtp.createServer((req) => {
+  req.on('to', filter)
+  req.on('message', (stream, ack) => save(req, stream, ack))
+  req.on('error', (err) => console.error(err))
+})
+
+server.listen(2525)
+
+function filter (to, {accept, reject}) {
+  const [user, host] = to.split('@')
+  if (hosts.has(host) && users.has(user)) {
+    accept()
+    return
+  }
+  reject(550, 'mailbox not available')
+}
+
+function save (req, stream, {accept}) {
+  const {from, to} = req
+  accept()
+  to.forEach((rcpt) => {
+    const [user] = rcpt.split('@')
+    const dest = path.join(mailDir, user, `${from}-${Date.now()}`)
+    const mail = fs.createWriteStream(dest)
+    mail.write(`From: ${from} \n`)
+    mail.write(`To: ${rcpt} \n\n`)
+    stream.pipe(mail, {end: false})
+  })
+}

Chapter05/creating-an-smtp-server/smtp-server/package.json

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+{
+  "name": "smtp",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "David Mark Clements",
+  "license": "MIT",
+  "dependencies": {
+    "smtp-protocol": "^2.4.7"
+  }
+}