[MC-101244] Can't scan for LAN worlds on macOS

For whatever reason, Minecraft on macOS can't scan for LAN worlds because of an error: "Unable to start LAN server detection"

[18:13:53] [Render thread/INFO]: Environment: authHost='https://authserver.mojang.com', accountsHost='https://api.mojang.com', sessionHost='https://sessionserver.mojang.com', servicesHost='https://api.minecraftservices.com', name='PROD'
[18:13:54] [Render thread/INFO]: Setting user: CatObsession
[18:13:55] [Render thread/INFO]: Backend library: LWJGL version 3.2.1 build 12
[18:14:00] [Render thread/INFO]: Reloading ResourceManager: Default
[18:14:16] [Render thread/INFO]: OpenAL initialized.
[18:14:16] [Render thread/INFO]: Sound engine started
[18:14:18] [Render thread/INFO]: Created: 1024x1024x4 minecraft:textures/atlas/blocks.png-atlas
[18:14:18] [Render thread/INFO]: Created: 256x128x4 minecraft:textures/atlas/signs.png-atlas
[18:14:18] [Render thread/INFO]: Created: 1024x512x4 minecraft:textures/atlas/banner_patterns.png-atlas
[18:14:18] [Render thread/INFO]: Created: 1024x512x4 minecraft:textures/atlas/shield_patterns.png-atlas
[18:14:18] [Render thread/INFO]: Created: 256x256x4 minecraft:textures/atlas/chest.png-atlas
[18:14:18] [Render thread/INFO]: Created: 512x256x4 minecraft:textures/atlas/beds.png-atlas
[18:14:18] [Render thread/INFO]: Created: 512x256x4 minecraft:textures/atlas/shulker_boxes.png-atlas
[18:14:22] [Render thread/INFO]: Created: 256x256x0 minecraft:textures/atlas/particles.png-atlas
[18:14:22] [Render thread/INFO]: Created: 256x256x0 minecraft:textures/atlas/paintings.png-atlas
[18:14:22] [Render thread/INFO]: Created: 256x128x0 minecraft:textures/atlas/mob_effects.png-atlas
[18:14:34] [Render thread/WARN]: Unable to start LAN server detection: Can't assign requested address
[18:20:31] [Render thread/INFO]: Stopping!

Workaround
Find your internal IP address (Windows, macOS) on the computer hosting the world, then on the other computer(s) go to the Multiplayer screen in Minecraft and click Direct Connect. Then on the hosts computer start the LAN world and take note of the message that says "LAN world hosted on Port xxxx". Then, on the other computer, in the Direct Connect field, put the internal IP address of the host computer followed by a colon ( : ) and then the number in the "LAN World hosted on Port xxxx" so for example 0.0.0.0:123456. You should now be able to connect.

Linked issues

is duplicated by 7

MC-101406 Unable to start LAN detection Resolved

MC-101855 LAN not connecting in Minecraft 1.9 Resolved

MC-113671 Cannot find LAN server Resolved

MC-119895 "io.netty.channel.AbstractChannel$AnnotatedConnectException: ConnectionRefused" while using LAN Resolved

MC-121113 "io.netty.channel.AbstractChannel$AnnotatedConnectException: ConnectionRefused" Resolved

2 more links

relates to 1

MC-98598 LAN List does not populate reliably Reopened

Attachments

latest.log

Comments 22

Yoshi83X 2016-11-21T23:03:59Z

Affects 1.11

Andy Molloy 2016-12-10T13:05:17Z

I was able to resolve this on my Mac (in 1.11) by forcing the JVM to use IPv4 by adding

-Djava.net.preferIPv4Stack=true

to the JVM arguments field in my profile.

Nancy OBrien 2016-12-16T00:50:25Z

This is driving me nuts! I have researched for days. Changed the java settings on the launcher window per a recommendation. Can we PLEASE FIX THIS??? Thank you.

Nancy OBrien 2016-12-17T05:43:41Z

Thank you. After the edit, this is what happens:
Unrecognized VM option 'Djava.net.preferIPv4Stack=true:-UseAdaptiveSizePolicy'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

I have spent so very long looking for answers for this!

Thorhallur 2017-07-15T22:41:19Z

This is still happening in 1.12.

Could you please fix this in code so we don't need to disable ipv6, or at the very least include the parameter mentioned by Andy Molloy above to the launcher defaults.

12 more comments

[Mod] violine1101 2017-10-13T16:32:28Z

The fix for MC-98598 might work here as well.

wobst.michael 2019-11-12T17:11:52Z

Please check if that's still an issue for you in the latest 1.14.4 stable release or the latest 1.15 development snapshot.

Ethan Foley-Lewis 2019-11-12T22:02:04Z

I'm am experiencing the same issue on snapshot 19w45b.

CreeperMagnet_ 2020-02-07T01:06:51Z

I can confirm this issue for the latest 1.16 snapshot, 20w06a. Same old issue.

Unable to start LAN server detection: Can't assign requested address

Winston Li 2020-04-21T02:23:45Z

The problems back. It first appeared while I was on 1.15.2. Thought it was either my firewall or my Java update. Came back 1 month later and it's still unresolved.

SpikeZarkSpike 2020-04-21T21:45:06Z

Still an issue on Java Edition 1.15.2 on Mac clients.

As this is easily fixed in the post.info why hasn't Mojang fixed it in the installer? It's beyond the technical ability of many users but trivial for the developer to fix.

SpikeZarkSpike 2020-04-21T21:53:06Z

In fact the scope of this is any Mac acting as a client. Even two Macs can't play with each other without the workaround to prefer IPv4 being set on all clients.

Winston Li 2020-04-21T22:38:03Z

ikr

James Rourke 2020-05-26T03:43:38Z

Whens it gonna be fixed

Winston Li 2020-06-23T23:06:31Z

1.16 is also affected. This better get fixed

Dot Burnett 2020-07-18T01:32:29Z

1.16.1 is also affected by this.

SpikeZarkSpike 2020-09-29T13:37:35Z

In terms of OS and models of Mac affected, it's going to affect all MacOSes other than truly ancient ones, and also certain Linux distros, because the root cause is the OS preferring IPv6 by default.

This is so easy to fix, the Minecraft launcher just needs to specify the Java option to force IPv4. Since LAN games only ever work over IPv4 (now and for the foreseeable future) I don't see any downside to just implementing this immediately. Certainly for the Mac launcher and probably across-the-board for all platforms would be totally fine.

ava gambhir 2020-11-03T21:22:34Z

This issue is still happening for me but I am not sure if it is the same.

So I want to join a LAN world and the person who has the LAN world is on a Macbook as am I. But no matter what I have done I cannot seem to join it. The world just will not show up and I have tried to change the current IPv6 to IPv4 but I am not sure how and when I try to type -Djava.net.preferIPv4Stack=true into JVM arguments it doesn't work. I have looked for how to enable JVM arguments but I can't find it. When I search the internet for answers anything remotely close to what I need is very outdated and unhelpful. This is the best thing I have found yet no resolution has been given.

Southpaw1496 2020-11-04T10:16:55Z

Did you try the workaround that I outlined in the bug's description?

SandmanDP 2021-05-13T20:16:41Z

Not sure if this has been the experience for everyone, but this problem appears to be resolved for me as of 21w19a. Possibly related to Java 16?

SPGoding 2021-05-20T23:06:21Z

Can someone still reproduce this issue in the latest development version?

[Mod] markderickson 2021-11-20T13:28:25Z

I can confirm that this has been fixed in 21w19a. 🙂