koot/libs/get-free-port.js

const portfinder = require('portfinder')

/**
 * 获取可用端口
 * @async
 * @param {Number|Number[]|Object} 正在使用、被占用或保留的端口
 * @returns {Number}
 */
module.exports = async (portUsed) => {

    const portStart = 3000
    const portEnd = 65535

    /** @type {Array[]} 使用 portfinder 检查的端口号范围组 */
    const ranges = [
        [portStart, portEnd]
    ]

    // console.log('portUsed', portUsed)

    /** @type {Number[]} 忽略的端口号 */
    const portsIgnore = []
    if (isNumber(portUsed)) {
        portsIgnore.push(parseInt(portUsed))
    } else if (Array.isArray(portUsed)) {
        portUsed.filter(value => isNumber(value))
            .forEach(port => portsIgnore.push(parseInt(port)))
    } else if (typeof portUsed === 'object') {
        Object.values(portUsed)
            .filter(value => isNumber(value))
            .forEach(port => portsIgnore.push(parseInt(port)))
    }

    // console.log('portsIgnore', portsIgnore)

    // 如果存在忽略的端口号，修改 ranges 为多组模式
    if (portsIgnore.length) {
        ranges.shift()
        let lastPort = portStart
        portsIgnore.forEach(port => {
            ranges.push([lastPort, port - 1])
            lastPort = port
        })
    }

    // console.log('ranges', ranges)

    for (let [start, end] of ranges) {
        const result = await getFreePort(start, end)
        // console.log(result)
        if (result)
            return result
    }
}

const isNumber = (value) => Boolean(
    typeof value === 'number' ||
    !isNaN(value)
)

/**
 * 获取范围内可用的端口
 * @param {Number} start 
 * @param {Number} end 
 * @returns {Number}
 */
const getFreePort = async (start, end) =>
    portfinder.getPortPromise({
        port: start,    // minimum port
        stopPort: end   // maximum port
    })
        .then((port) => {
            //
            // `port` is guaranteed to be a free port
            // in this scope.
            //
            return port
        })
        .catch((/*err*/) => {
            //
            // Could not get a free port, `err` contains the reason.
            //
        })