Created
March 5, 2026 05:48
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Free up a TCP port by killing all processes listening on it, properly
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| /** | |
| * Free-up a TCP port by killing all processes listening on it. | |
| * | |
| * - Sends SIGTERM, polls until dead or timeout | |
| * - Escalates to SIGKILL on timeout | |
| * - Returns array of killed PIDs, empty if none | |
| * | |
| * await unbind(3000) // => [] or [pid, ...] | |
| * await unbind(3000, { timeout: 5000 }) // longer grace period | |
| * await unbind(3000, { // slower polling | |
| * poll: { interval: 100 } | |
| * }) | |
| */ | |
| import { execFile } from 'node:child_process' | |
| import { promisify } from 'node:util' | |
| import { setTimeout as wait } from 'node:timers/promises' | |
| export const unbind = (port, { | |
| timeout = 3000, | |
| poll: { interval = 50 } = {} | |
| } = {}) => | |
| Promise.resolve(port) | |
| .then(port => Number.isFinite(port) && port >= 1 && port <= 65535 | |
| ? port | |
| : Promise.reject(new RangeError(`port: ${port}, must be 1 - 65535`))) | |
| .then(port => promisify(execFile)('lsof', ['-ti', `tcp:${port}`, '-sTCP:LISTEN'])) | |
| .then(({ stdout }) => stdout.trim().split('\n').map(Number).filter(Boolean)) | |
| .then(pids => pids.map(pid => (process.kill(pid, 'SIGTERM'), pid))) | |
| .then(function poll(pids, start = Date.now()) { | |
| const live = pids.filter(pid => { | |
| try { return process.kill(pid, 0), true } | |
| catch (err) { | |
| if (err.code === 'ESRCH') return false | |
| throw err | |
| } | |
| }) | |
| return !live.length ? pids : | |
| Date.now() - start >= timeout | |
| ? (live.forEach(pid => process.kill(pid, 'SIGKILL')), pids) | |
| : wait(Math.max(10, interval)).then(() => poll(pids, start)) | |
| }) | |
| .catch(err => err.code === 1 ? [] : Promise.reject(err)) |
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