Undici aligns with the Node.js LTS schedule. The following table shows the supported versions:

| Version | Node.js | End of Life |

|---------|-------------|-------------|

| 5.x | v18.x | 2024-04-30 |

| 6.x | v20.x v22.x | 2026-04-30 |

| 7.x | v24.x | 2027-04-30 |

| Undici Version | Bundled in Node.js | Node.js Versions Supported | End of Life |

|----------------|-------------------|----------------------------|-------------|

| 5.x | 18.x | ≥14.0 (tested: 14, 16, 18) | 2024-04-30 |

| 6.x | 20.x, 22.x | ≥18.17 (tested: 18, 20, 21, 22) | 2026-04-30 |

| 7.x | 24.x | ≥20.18.1 (tested: 20, 22, 24) | 2027-04-30 |

## License

```js

import diagnosticsChannel from 'diagnostics_channel'

diagnosticsChannel.channel('undici:websocket:open').subscribe(({ address, protocol, extensions, websocket }) => {

diagnosticsChannel.channel('undici:websocket:open').subscribe(({

address, // { address: string, family: string, port: number }

protocol, // string - negotiated subprotocol

extensions, // string - negotiated extensions

websocket, // WebSocket - the WebSocket instance

handshakeResponse // object - HTTP response that upgraded the connection

}) => {

console.log(address) // address, family, and port

console.log(protocol) // negotiated subprotocols

console.log(extensions) // negotiated extensions

console.log(websocket) // the WebSocket instance

// Handshake response details

console.log(handshakeResponse.status) // 101 for successful WebSocket upgrade

console.log(handshakeResponse.statusText) // 'Switching Protocols'

console.log(handshakeResponse.headers) // Object containing response headers

})

```

### Handshake Response Object

The `handshakeResponse` object contains the HTTP response that upgraded the connection to WebSocket:

- `status` (number): The HTTP status code (101 for successful WebSocket upgrade)

- `statusText` (string): The HTTP status message ('Switching Protocols' for successful upgrade)

- `headers` (object): The HTTP response headers from the server, including:

- `upgrade: 'websocket'`

- `connection: 'upgrade'`

- `sec-websocket-accept` and other WebSocket-related headers

This information is particularly useful for debugging and monitoring WebSocket connections, as it provides access to the initial HTTP handshake response that established the WebSocket connection.

## `undici:websocket:close`

This message is published after the connection has closed.

'use strict'

const { kProxy, kClose, kDestroy, kDispatch } = require('../core/symbols')

const { URL } = require('node:url')

const Agent = require('./agent')

const Pool = require('./pool')

const DispatcherBase = require('./dispatcher-base')

}

/**

* @param {import('../types/proxy-agent').ProxyAgent.Options | string | URL} opts

* @param {import('../../types/proxy-agent').ProxyAgent.Options | string | URL} opts

* @returns {URL}

*/

#getUrl (opts) {

200, 203, 204, 206, 300, 301, 308, 404, 405, 410, 414, 501

]

// Status codes which semantic is not handled by the cache

// https://datatracker.ietf.org/doc/html/rfc9111#section-3

// This list should not grow beyond 206 and 304 unless the RFC is updated

// by a newer one including more. Please introduce another list if

// implementing caching of responses with the 'must-understand' directive.

const NOT_UNDERSTOOD_STATUS_CODES = [

206, 304

]

const MAX_RESPONSE_AGE = 2147483647000

/**

* @param {import('../../types/cache-interceptor.d.ts').default.CacheControlDirectives} cacheControlDirectives

*/

function canCacheResponse (cacheType, statusCode, resHeaders, cacheControlDirectives) {

// Allow caching for status codes 200 and 307 (original behavior)

// Also allow caching for other status codes that are heuristically cacheable

// when they have explicit cache directives

if (statusCode !== 200 && statusCode !== 307 && !HEURISTICALLY_CACHEABLE_STATUS_CODES.includes(statusCode)) {

// Status code must be final and understood.

if (statusCode < 200 || NOT_UNDERSTOOD_STATUS_CODES.includes(statusCode)) {

return false

}

// Responses with neither status codes that are heuristically cacheable, nor "explicit enough" caching

// directives, are not cacheable. "Explicit enough": see https://www.rfc-editor.org/rfc/rfc9111.html#section-3

if (!HEURISTICALLY_CACHEABLE_STATUS_CODES.includes(statusCode) && !resHeaders['expires'] &&

!cacheControlDirectives.public &&

cacheControlDirectives['max-age'] === undefined &&

// RFC 9111: a private response directive, if the cache is not shared

!(cacheControlDirectives.private && cacheType === 'private') &&

!(cacheControlDirectives['s-maxage'] !== undefined && cacheType === 'shared')

) {

return false

}

const CacheHandler = require('../handler/cache-handler')

const MemoryCacheStore = require('../cache/memory-cache-store')

const CacheRevalidationHandler = require('../handler/cache-revalidation-handler')

const { assertCacheStore, assertCacheMethods, makeCacheKey, normaliseHeaders, parseCacheControlHeader } = require('../util/cache.js')

const { assertCacheStore, assertCacheMethods, makeCacheKey, normalizeHeaders, parseCacheControlHeader } = require('../util/cache.js')

const { AbortError } = require('../core/errors.js')

/**

opts = {

...opts,

headers: normaliseHeaders(opts)

headers: normalizeHeaders(opts)

}

const reqCacheControl = opts.headers?.['cache-control']

> undici@7.13.0 build:wasm

> undici@7.14.0 build:wasm

> node build/wasm.js --docker

> docker run --rm --platform=linux/x86_64 --user 1001:118 --mount type=bind,source=/home/runner/work/node/node/deps/undici/src/lib/llhttp,target=/home/node/build/lib/llhttp --mount type=bind,source=/home/runner/work/node/node/deps/undici/src/build,target=/home/node/build/build --mount type=bind,source=/home/runner/work/node/node/deps/undici/src/deps,target=/home/node/build/deps -t ghcr.io/nodejs/wasm-builder@sha256:975f391d907e42a75b8c72eb77c782181e941608687d4d8694c3e9df415a0970 node build/wasm.js