net: add createPipe() and createSocketPair() by kingces95 · Pull Request #65094 · nodejs/node

kingces95 · 2026-08-07T00:55:51Z

Adds a node:pipe module with createPipe(), returning a readable and writable endpoint owned by the parent process.

The endpoints may be passed to child_process.spawn() stdio. This lets the parent lend a pipe endpoint to a child without turning the parent stream itself into child-owned stdio. The parent can then reclaim unread bytes or lend the same endpoint to a later child.

This is useful for bash-like partial consumption of long-lived streams. For example, a parent can keep ownership of a Server Sent Event stream while delegating bounded reads to external tools, then continue parsing from the exact byte where the child stopped.

Endpoints created by pipe.createPipe() are rejected by spawnSync(), and an endpoint may only be leased to one child process at a time.

After moving to net module, found socket pair to be a similarly untapped libuv export so included that. So now:

net.createPipe() exposes directional OS-backed endpoints: { readable, writable }.
net.createSocketPair() exposes symmetric duplex OS-backed endpoints: [left, right].
Pipe endpoints can be leased directly to child process stdio, because that maps cleanly to inherited pipe handles on both Unix and Windows.
Socket-pair endpoints are not accepted as stdio; instead, they use Node’s existing IPC handle-transfer path with subprocess.send(), which matches how socket-like handles already cross process boundaries.
The parent process owns the endpoint lifecycle, so docs now call out normal stream cleanup: end(), consumption, resume(), or destroy() as appropriate.

net.createPipe

Child process 'sips' just a single character from the pipe leaving parent to drain what's left.

const { spawn } = require('node:child_process');
const { createPipe } = require('node:net');
const { text } = require('node:stream/consumers');

const { readable, writable } = createPipe();
const child = spawn(process.execPath, ['-e', `
  const fs = require('node:fs');
  const buffer = Buffer.alloc(1);
  const count = fs.readSync(0, buffer, 0, 1, null);
  fs.writeSync(1, buffer.subarray(0, count));
`], {
  stdio: [readable, 'pipe', 'inherit'],
});

const output = text(child.stdout);
writable.end('abc');

child.on('close', async () => {
  console.log(await output); // Prints: a
  console.log(await text(readable)); // Prints: bc
});

net.createSocketPair()

Child process echos parent message over a socket pair.

const { spawn } = require('node:child_process');
const { createSocketPair } = require('node:net');

const [left, right] = createSocketPair();

const child = spawn(process.execPath, ['-e', `
  process.on('message', (message, socket) => {
    socket.on('data', (chunk) => {
      socket.write(chunk.toString().toUpperCase());
    });
    socket.resume();
    process.send('ready');
  });
`], {
  stdio: ['ignore', 'inherit', 'inherit', 'ipc'],
});

child.once('message', () => {
  left.write('hello');
});

left.once('data', (chunk) => {
  console.log(chunk.toString()); // Prints: HELLO
  left.destroy();
  child.kill();
});

child.send('socket', right, { keepOpen: false });

Thank you for considering my pull request!

marco-ippolito · 2026-08-07T12:23:52Z

I dont think we should create a new module

jasnell · 2026-08-07T12:57:29Z

+1, there's no justification for a new top-level module.

kingces95 · 2026-08-07T20:49:34Z

Yep. I'll move it to net.

kingces95 · 2026-08-09T06:07:27Z

I also pushed a small stacked follow-up branch that explores the adjacent uv_socketpair() primitive as net.createSocketPair():

kingces95/node@create-pipe...create-socket-pair

My immediate use case is net.createPipe(); I’m offering this for completeness if reviewers think these APIs should be considered as a small family.

The idea is that net.createPipe() exposes directional OS-backed endpoints, while net.createSocketPair() exposes symmetric duplex OS-backed endpoints, similar in shape to stream.duplexPair() but with real handles.

The follow-up has child-process support for fd >= 3, where the duplex nature is explicit.

kingces95 · 2026-08-10T00:41:59Z

I folded the socket-pair follow-up into the main change.

The updated version keeps both APIs in node:net:

net.createPipe() returns directional parent-owned endpoints.
net.createSocketPair() returns a symmetric duplex pair.
Both can be leased to child processes through stdio, with createSocketPair() limited to fd >= 3.
The bash/SSE sketch was removed from the test suite.

This should make the PR easier to review as one coherent “parent-owned OS endpoints” feature.

The removed sketch is preserved here as a userland workbook/example of the style of shell-like stream composition this API is meant to enable:

https://gist.github.com/kingces95/1e024a1e987ef3956c7ae3513e468c64

Signed-off-by: Chris King <kingces95@gmail.com>

kingces95 · 2026-08-10T07:32:18Z

I landed on a single coherent node:net feature shape:

net.createPipe() exposes directional OS-backed endpoints: { readable, writable }.
net.createSocketPair() exposes symmetric duplex OS-backed endpoints: [left, right].
Pipe endpoints can be leased directly to child process stdio, because that maps cleanly to inherited pipe handles on both Unix and Windows.
Socket-pair endpoints are not accepted as stdio; instead, they use Node’s existing IPC handle-transfer path with subprocess.send(), which matches how socket-like handles already cross process boundaries.
The parent process owns the endpoint lifecycle, so docs now call out normal stream cleanup: end(), consumption, resume(), or destroy() as appropriate.

So the PR is no longer “just create pipe.” It is a parent-owned OS endpoint proposal: pipes for directional stdio leasing, socket pairs for duplex cross-process communication.

nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. lib / src Issues and PRs related to general changes in the lib or src directory. needs-ci PRs that need a full CI run. labels Aug 7, 2026

kingces95 marked this pull request as ready for review August 7, 2026 01:52

kingces95 changed the title ~~net: add parent-owned pipe endpoints~~ net: add createPipe() Aug 7, 2026

kingces95 force-pushed the create-pipe branch 4 times, most recently from 83d8402 to db5d657 Compare August 7, 2026 20:33

kingces95 force-pushed the create-pipe branch from db5d657 to 84cfdb8 Compare August 7, 2026 21:14

kingces95 force-pushed the create-pipe branch from 84cfdb8 to 50be671 Compare August 10, 2026 00:36

kingces95 force-pushed the create-pipe branch 4 times, most recently from 3621fab to 3c6c2d0 Compare August 10, 2026 06:07

kingces95 marked this pull request as draft August 10, 2026 06:25

net: add parent-owned pipe and socket endpoints

cefffac

Signed-off-by: Chris King <kingces95@gmail.com>

kingces95 force-pushed the create-pipe branch from 3c6c2d0 to cefffac Compare August 10, 2026 07:29

kingces95 marked this pull request as ready for review August 10, 2026 07:33

kingces95 changed the title ~~net: add createPipe()~~ net: add createPipe() and createSocketPair() Aug 10, 2026

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net: add createPipe() and createSocketPair() - #65094

net: add createPipe() and createSocketPair()#65094
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