The tcp-port-used npm package is a utility for checking the status of TCP ports. It allows you to determine if a specific port is in use, wait for a port to become available, or wait for a port to be used. This can be particularly useful for network-related tasks, such as ensuring that a server has started or stopped correctly.

What are tcp-port-used's main functionalities?

Check if a port is in use

This feature allows you to check if a specific TCP port is currently in use. The code sample demonstrates how to check if port 8080 is in use and logs the result.

const tcpPortUsed = require('tcp-port-used');

const port = 8080;
tcpPortUsed.check(port)
  .then(inUse => {
    console.log(`Port ${port} is ${inUse ? 'in use' : 'free'}`);
  })
  .catch(err => {
    console.error('Error on check:', err.message);
  });

Wait for a port to become available

This feature allows you to wait until a specific TCP port becomes available. The code sample demonstrates how to wait until port 8080 is free, checking every 500ms for up to 30 seconds.

const tcpPortUsed = require('tcp-port-used');

const port = 8080;
tcpPortUsed.waitUntilFree(port, 500, 30000)
  .then(() => {
    console.log(`Port ${port} is now free`);
  })
  .catch(err => {
    console.error('Error on waitUntilFree:', err.message);
  });

Wait for a port to be used

This feature allows you to wait until a specific TCP port is in use. The code sample demonstrates how to wait until port 8080 is in use, checking every 500ms for up to 30 seconds.

const tcpPortUsed = require('tcp-port-used');

const port = 8080;
tcpPortUsed.waitUntilUsed(port, 500, 30000)
  .then(() => {
    console.log(`Port ${port} is now in use`);
  })
  .catch(err => {
    console.error('Error on waitUntilUsed:', err.message);
  });

Other packages similar to tcp-port-used

tcp-port-used

A simple Node.js module to check if a TCP port is currently in use. It returns a deferred promise from the q library.

Installation

npm install tcp-port-used

Examples

To check a port's state:

var tcpPortUsed = require('tcp-port-used');

tcpPortUsed.check(44201, '127.0.0.1')
.then(function(inUse) {
    console.log('Port 44201 usage: '+inUse);
}, function(err) {
    console.error('Error on check:', err.message);
});

To wait until a port on localhost is available:

tcpPortUsed.waitUntilFree(44203, 500, 4000)
.then(function() {
    console.log('Port 44203 is now free.');
}, function(err) {
    console.log('Error:', err.message);
});

To wait until a port on a host is available:

tcpPortUsed.waitUntilFreeOnHost(44203, 'some.host.com', 500, 4000)
.then(function() {
    console.log('Port 44203 on some.host.com is now free.');
}, function(err) {
    console.log('Error:', err.message);
});

To wait until a port on localhost is accepting connections:

tcpPortUsed.waitUntilUsed(44204, 500, 4000)
.then(function() {
    console.log('Port 44204 is now in use.');
}, function(err) {
    console.log('Error:', err.message);
});

To wait until a port on a host is accepting connections:

tcpPortUsed.waitUntilUsedOnHost(44204, 'some.host.com', 500, 4000)
.then(function() {
    console.log('Port 44204 on some.host.com is now in use.');
}, function(err) {
    console.log('Error:', err.message);
});

To wait until a port on a host is in specific state:

var inUse = true;   // wait until the port is in use
tcpPortUsed.waitForStatus(44204, 'some.host.com', inUse, 500, 4000)
.then(function() {
    console.log('Port 44204 on some.host.com is now in use.');
}, function(err) {
    console.log('Error:', err.message);
});

API

check(port [, host])

Checks if a TCP port is in use by attempting to connect to the port on host. If no host is specified, the module uses '127.0.0.1' (localhost). When the promise is resolved, there is a parameter inUse, when true means the port is in use and false means the port is free.

Parameters:

Number|Object port The port you are curious to see if available. If an object, must contain all the parameters as properties.
String host The host name or IP address of the host. Default, if not defined: '127.0.0.1'

Returns: