From 96a4417bb9ba49607a58e97d0bc1f987c33184bb Mon Sep 17 00:00:00 2001 From: James M Snell Date: Thu, 18 Oct 2018 18:12:59 -0700 Subject: [PATCH] doc: document that addMembership must be called once in a cluster Fixes: https://github.com/nodejs/node/issues/12572 Refs: https://github.com/nodejs/node/pull/16240 PR-URL: https://github.com/nodejs/node/pull/23746 Reviewed-By: Refael Ackermann Reviewed-By: Luigi Pinca Reviewed-By: Trivikram Kamat --- doc/api/dgram.md | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/doc/api/dgram.md b/doc/api/dgram.md index 93a1d186e7c620..6553c4a0323ced 100644 --- a/doc/api/dgram.md +++ b/doc/api/dgram.md @@ -95,6 +95,24 @@ Tells the kernel to join a multicast group at the given `multicastAddress` and one interface and will add membership to it. To add membership to every available interface, call `addMembership` multiple times, once per interface. +When sharing a UDP socket across multiple `cluster` workers, the +`socket.addMembership()` function must be called only once or an +`EADDRINUSE` error will occur: + +```js +const cluster = require('cluster'); +const dgram = require('dgram'); +if (cluster.isMaster) { + cluster.fork(); // Works ok. + cluster.fork(); // Fails with EADDRINUSE. +} else { + const s = dgram.createSocket('udp4'); + s.bind(1234, () => { + s.addMembership('224.0.0.114'); + }); +} +``` + ### socket.address()