denoland/deno · error · TypeError

Invalid port

Error message

Invalid port: '${maybePort}'

What it means

Thrown by Deno's port validator (validatePort in ext/net/01_net.js) when the port is a string that cannot be converted to a number: Number(maybePort) is NaN while the input itself is not NaN. It is a TypeError raised before any socket is created. Every port passed to Deno.connect, Deno.listen, Deno.connectTls, and Deno.listenDatagram goes through this check.

Solutions

1. Pass the port as a number: Deno.connect({ hostname, port: 5432 })
2. Coerce values from env/config at the boundary: const port = Number(raw); if (!Number.isInteger(port)) fail fast with a clear config error
3. If the value comes from a URL, extract it with new URL(str).port and Number() it before calling

Example fix

// before
Deno.connect({ port: Deno.env.get('PORT') }); // PORT='auto' -> Invalid port: 'auto'

// after
const raw = Deno.env.get('PORT') ?? '8080';
const port = Number(raw);
if (!Number.isInteger(port) || port < 1 || port > 65535) {
  throw new Error(`Invalid PORT value: ${raw}`);
}
Deno.connect({ port });

function parsePort(raw: unknown): number {
  if (typeof raw !== 'number' && typeof raw !== 'string') throw new TypeError('port must be number or string');
  if (raw === '') throw new TypeError('port must not be empty');
  const n = Number(raw);
  if (!Number.isInteger(n)) throw new TypeError(`Invalid port: ${String(raw)}`);
  return n;
}
// const port = parsePort(Deno.env.get('PORT')); Deno.connect({ port });

function isValidPortSpec(p: unknown): p is number | string {
  if (p === '' || p === null || p === undefined) return false;
  return Number.isInteger(Number(p));
}

try {
  await Deno.connect({ port });
} catch (e) {
  if (e instanceof TypeError && e.message.startsWith('Invalid port')) {
    throw new Error(`Bad port in configuration: ${JSON.stringify(portArg)}`);
  }
  throw e;
}

When it happens

Trigger: Deno.connect({ hostname: 'db', port: 'localhost' }) (hostname value placed in the port field); Deno.listen({ port: '8080a' }); Deno.listenDatagram({ transport: 'udp', port: 'auto' }) where a non-numeric env/config string is forwarded.

Common situations: Swapping hostname and port arguments; reading the port from an environment variable or config file that contains text like 'auto', 'default', or 'PORT'; passing a full URL string ('localhost:5432') instead of just the port component.

Related errors

• Invalid port
• Invalid port: ''
• Invalid port (out of range)
• The provided value " " is not a valid permission name
• Unsupported transport

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/65b0339961b5abc2. Report an issue: GitHub.

Appendix: source

Thrown at ext/net/01_net.js:651

      throw new TypeError(`Unsupported transport: '${transport}'`);
  }
}

function validatePort(maybePort, isServer = false) {
  // A missing port means "any available port" (port 0) for servers. Clients
  // must always specify a port to connect to, so a missing port is left as-is
  // and rejected below.
  if (isServer && (maybePort === null || maybePort === undefined)) {
    maybePort = 0;
  }
  if (typeof maybePort !== "number" && typeof maybePort !== "string") {
    throw new TypeError(`Invalid port (expected number): ${maybePort}`);
  }
  if (maybePort === "") throw new TypeError("Invalid port: ''");
  const port = Number(maybePort);
  if (!NumberIsInteger(port)) {
    if (NumberIsNaN(port) && !NumberIsNaN(maybePort)) {
      throw new TypeError(`Invalid port: '${maybePort}'`);
    } else {
      throw new TypeError(`Invalid port: ${maybePort}`);
    }
  } else if (port < (isServer ? 0 : 1) || port > 65535) {
    // Servers may bind to port 0 (OS-assigned), clients may not connect to it.
    throw new RangeError(`Invalid port (out of range): ${maybePort}`);
  }
  return port;
}

function createListenDatagram(udpOpFn, unixOpFn) {
  return function listenDatagram(args) {
    switch (args.transport) {
      case "udp": {
        const port = validatePort(args.port, true);
        const { 0: rid, 1: addr } = udpOpFn(
          {
            hostname: args.hostname ?? "0.0.0.0",

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