feat: add reserved port validation

errors/reserved-port.mdx

@@ -0,0 +1,27 @@
+---
+title: Reserved Port
+---
+
+## Why This Error Occurred
+
+Server was started on a reserved port. For example, `4045` is reserved for the Network Paging Protocol (npp).
+
+```
+next start -p 4045
+```
+
+or
+
+```
+next dev --port 4045
+```
+
+Starting the server on a reserved port will result in an error.
+
+## Possible Ways to Fix It
+
+Change the provided port to ensure it's not listed in the [Port Blocking](https://fetch.spec.whatwg.org/#port-blocking) section of WHATWG's fetch spec.
+
+## Useful Links
+
+- https://fetch.spec.whatwg.org/#port-blocking

packages/next/src/cli/next-dev.ts

@@ -18,6 +18,10 @@ import uploadTrace from '../trace/upload-trace'
 import { startServer } from '../server/lib/start-server'
 import { loadEnvConfig } from '@next/env'
 import { trace } from '../trace'
+import {
+  getReservedPortExplanation,
+  isPortIsReserved,
+} from '../lib/helpers/get-reserved-port'
 
 let dir: string
 let config: NextConfigComplete
@@ -167,6 +171,11 @@ const nextDev: CliCommand = async (args) => {
   }
 
   const port = getPort(args)
+
+  if (isPortIsReserved(port)) {
+    printAndExit(getReservedPortExplanation(port), 1)
+  }
+
   // If neither --port nor PORT were specified, it's okay to retry new ports.
   const allowRetry =
     args['--port'] === undefined && process.env.PORT === undefined

packages/next/src/cli/next-start.ts

@@ -4,6 +4,10 @@ import { startServer } from '../server/lib/start-server'
 import { getPort, printAndExit } from '../server/lib/utils'
 import { getProjectDir } from '../lib/get-project-dir'
 import { CliCommand } from '../lib/commands'
+import {
+  getReservedPortExplanation,
+  isPortIsReserved,
+} from '../lib/helpers/get-reserved-port'
 
 const nextStart: CliCommand = async (args) => {
   if (args['--help']) {
@@ -31,6 +35,10 @@ const nextStart: CliCommand = async (args) => {
   const host = args['--hostname']
   const port = getPort(args)
 
+  if (isPortIsReserved(port)) {
+    printAndExit(getReservedPortExplanation(port), 1)
+  }
+
   const isExperimentalTestProxy = args['--experimental-test-proxy']
 
   const keepAliveTimeoutArg: number | undefined = args['--keepAliveTimeout']

packages/next/src/lib/helpers/get-reserved-port.ts

@@ -0,0 +1,96 @@
+/** https://fetch.spec.whatwg.org/#port-blocking */
+export const KNOWN_RESERVED_PORTS = {
+  1: 'tcpmux',
+  7: 'echo',
+  9: 'discard',
+  11: 'systat',
+  13: 'daytime',
+  15: 'netstat',
+  17: 'qotd',
+  19: 'chargen',
+  20: 'ftp-data',
+  21: 'ftp',
+  22: 'ssh',
+  23: 'telnet',
+  25: 'smtp',
+  37: 'time',
+  42: 'name',
+  43: 'nicname',
+  53: 'domain',
+  69: 'tftp',
+  77: 'rje',
+  79: 'finger',
+  87: 'link',
+  95: 'supdup',
+  101: 'hostname',
+  102: 'iso-tsap',
+  103: 'gppitnp',
+  104: 'acr-nema',
+  109: 'pop2',
+  110: 'pop3',
+  111: 'sunrpc',
+  113: 'auth',
+  115: 'sftp',
+  117: 'uucp-path',
+  119: 'nntp',
+  123: 'ntp',
+  135: 'epmap',
+  137: 'netbios-ns',
+  139: 'netbios-ssn',
+  143: 'imap',
+  161: 'snmp',
+  179: 'bgp',
+  389: 'ldap',
+  427: 'svrloc',
+  465: 'submissions',
+  512: 'exec',
+  513: 'login',
+  514: 'shell',
+  515: 'printer',
+  526: 'tempo',
+  530: 'courier',
+  531: 'chat',
+  532: 'netnews',
+  540: 'uucp',
+  548: 'afp',
+  554: 'rtsp',
+  556: 'remotefs',
+  563: 'nntps',
+  587: 'submission',
+  601: 'syslog-conn',
+  636: 'ldaps',
+  989: 'ftps-data',
+  990: 'ftps',
+  993: 'imaps',
+  995: 'pop3s',
+  1719: 'h323gatestat',
+  1720: 'h323hostcall',
+  1723: 'pptp',
+  2049: 'nfs',
+  3659: 'apple-sasl',
+  4045: 'npp',
+  5060: 'sip',
+  5061: 'sips',
+  6000: 'x11',
+  6566: 'sane-port',
+  6665: 'ircu',
+  6666: 'ircu',
+  6667: 'ircu',
+  6668: 'ircu',
+  6669: 'ircu',
+  6697: 'ircs-u',
+  10080: 'amanda',
+} as const
+
+type ReservedPort = keyof typeof KNOWN_RESERVED_PORTS
+
+export function isPortIsReserved(port: number): port is ReservedPort {
+  return port in KNOWN_RESERVED_PORTS
+}
+
+export function getReservedPortExplanation(port: ReservedPort): string {
+  return (
+    `Bad port: "${port}" is reserved for ${KNOWN_RESERVED_PORTS[port]}\n` +
+    'Read more: https://nextjs.org/docs/messages/reserved-port'
+  )
+}

test/integration/cli/test/index.test.js

@@ -19,6 +19,37 @@ import stripAnsi from 'strip-ansi'
 const dirBasic = join(__dirname, '../basic')
 const dirDuplicateSass = join(__dirname, '../duplicate-sass')
 
+const runAndCaptureOutput = async ({ port }) => {
+  let stdout = ''
+  let stderr = ''
+
+  let app = http.createServer((_, res) => {
+    res.writeHead(200, { 'Content-Type': 'text/plain' })
+    res.end('OK')
+  })
+
+  await new Promise((resolve, reject) => {
+    app.on('error', reject)
+    app.on('listening', () => resolve())
+    app.listen(port)
+  })
+
+  await launchApp(dirBasic, port, {
+    stdout: true,
+    stderr: true,
+    onStdout(msg) {
+      stdout += msg
+    },
+    onStderr(msg) {
+      stderr += msg
+    },
+  })
+
+  await new Promise((resolve) => app.close(resolve))
+
+  return { stdout, stderr }
+}
+
 const testExitSignal = async (
   killSignal = '',
   args = [],
@@ -208,6 +239,32 @@ describe('CLI Usage', () => {
         'Invalid keep alive timeout provided, expected a non negative number'
       )
     })
+
+    test('should not start on a port out of range', async () => {
+      const invalidPort = '300001'
+      const { stderr } = await runNextCommand(
+        ['start', '--port', invalidPort],
+        {
+          stderr: true,
+        }
+      )
+
+      expect(stderr).toContain(`options.port should be >= 0 and < 65536.`)
+    })
+
+    test('should not start on a reserved port', async () => {
+      const reservedPort = '4045'
+      const { stderr } = await runNextCommand(
+        ['start', '--port', reservedPort],
+        {
+          stderr: true,
+        }
+      )
+
+      expect(stderr).toContain(
+        `Bad port: "${reservedPort}" is reserved for npp`
+      )
+    })
   })
 
   describe('no command', () => {
@@ -464,37 +521,27 @@ describe('CLI Usage', () => {
 
     test('-p conflict', async () => {
       const port = await findPort()
+      const { stderr, stdout } = await runAndCaptureOutput({ port })
 
-      let app = http.createServer((_, res) => {
-        res.writeHead(200, { 'Content-Type': 'text/plain' })
-        res.end('OK')
-      })
-      await new Promise((resolve, reject) => {
-        // This code catches EADDRINUSE error if the port is already in use
-        app.on('error', reject)
-        app.on('listening', () => resolve())
-        app.listen(port)
-      })
-      let stdout = '',
-        stderr = ''
-      await launchApp(dirBasic, port, {
-        stdout: true,
-        stderr: true,
-        onStdout(msg) {
-          stdout += msg
-        },
-        onStderr(msg) {
-          stderr += msg
-        },
-      })
-      await new Promise((resolve) => app.close(resolve))
       expect(stderr).toMatch('already in use')
       expect(stdout).not.toMatch('ready')
       expect(stdout).not.toMatch('started')
       expect(stdout).not.toMatch(`${port}`)
       expect(stripAnsi(stdout).trim()).toBeFalsy()
     })
 
+    test('-p reserved', async () => {
+      const TCP_MUX_PORT = 1
+      const { stderr, stdout } = await runAndCaptureOutput({
+        port: TCP_MUX_PORT,
+      })
+
+      expect(stdout).toMatch('')
+      expect(stderr).toMatch(
+        `Bad port: "${TCP_MUX_PORT}" is reserved for tcpmux`
+      )
+    })
+
     test('--hostname', async () => {
       const port = await findPort()
       let output = ''