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Get an availableTCP port.

npm install get-port

importgetPortfrom'get-port';console.log(awaitgetPort());//=> 51402

Pass in a preferred port:

importgetPortfrom'get-port';console.log(awaitgetPort({port:3000}));// Will use 3000 if available, otherwise fall back to a random port

Pass in an array of preferred ports:

importgetPortfrom'get-port';console.log(awaitgetPort({port:[3000,3001,3002]}));// Will use any element in the preferred ports array if available, otherwise fall back to a random port

Use theportNumbers() helper in case you need a port in a certain range:

importgetPort,{portNumbers}from'get-port';console.log(awaitgetPort({port:portNumbers(3000,3100)}));// Will use any port from 3000 to 3100, otherwise fall back to a random port

Returns aPromise for a port number.

Type:object

Type:number | Iterable<number>

A preferred port or an iterable of preferred ports to use.

Type:Iterable<number>

Ports that should not be returned.

You could, for example, pass it the return value of theportNumbers() function.

Type:string

The host on which port resolution should be performed. Can be either an IPv4 or IPv6 address.

By default, it checks availability on all local addresses defined inOS network interfaces. If this option is set, it will only check the given host.

Generate port numbers in the given rangefrom...to.

Returns anIterable for port numbers in the given range.

importgetPort,{portNumbers}from'get-port';console.log(awaitgetPort({port:portNumbers(3000,3100)}));// Will use any port from 3000 to 3100, otherwise fall back to a random port

Type:number

The first port of the range. Must be in the range1024...65535.

Type:number

The last port of the range. Must be in the range1024...65535 and must be greater thanfrom.

Clear the internal cache of locked ports.

This can be useful when you want the results to be unaffected by previous calls.

Please note that clearing the cache removes protection againstin-process race conditions.

importgetPort,{clearLockedPorts}from'get-port';constport=[3000,3001,3002];console.log(awaitgetPort({port}));//=> 3000console.log(awaitgetPort({port}));//=> 3001// If you want the results to be unaffected by previous calls, clear the cache.clearLockedPorts();console.log(awaitgetPort({port}));//=> 3000

There is a very tiny chance of a race condition if another process starts using the same port number as you in between the time you get the port number and you actually start using it.

In-process race conditions (such as when running parallel Jest tests) are completely eliminated by a lightweight locking mechanism where returned ports are held for 15-30 seconds before being eligible for reuse.

Multi-process race conditions are extremely rare and will result in an immediateEADDRINUSE error when attempting to bind to the port, allowing your application to retry.

• get-port-cli - CLI for this module