LAN List does not populate reliably

Yes - there is a firewall in settings on a Mac (came late in OSX development and many ask why) - no one use that - and as said - it's not on as default 'cause in Mac-universe no one cares about firewalls in OS (it's a Windows-thing).

Confirming: Direct Connect don't work. Gives:
java.net.ConnectionExeption: Connection refused.

I suppose you have Macs so you can see the real world yourself? Or is it only Win-machines in your lab?

I asked you because I was able to use direct connect on my Mac, confirming this is not a Mac issue and instead is a technical support issue! So, without further ado,

This is a technical support issue; this site is for bug reports only. For technical support please use the Mojang Support Center.

So - I'm able to play MC over LAN with 1.8 - but not 1.9. And it's not a bug as you say...then I suppose it's a JAVA-thing. Ditect Connect gives "java.net.ConnectionExeption: Connection refused". I just wait for an JAVA update then.

Note: I can connect to MC-servers on Internet (some have updated now). So - my JAVA is OK for connecting over Internet - but not over LAN.

Please force a crash by pressing F3 + C for 10 seconds while in-game and attach the crash report ([minecraft|http://hopper.minecraft.net/help/finding-minecraft-data-folder]/crash-reports/crash-<DATE>-client.txt) here.

This can be done in a single player world.

Crash report

Direct connect works! But as LAN gives random number every time you LAN out a world it's not practical...my kids don't fix this to have to enter IP plus port number every time.
So - my theory is that MC 1.9 don't scan for LAN'ed MC's on local network...no scanning at all...maybe it scans IP but not port numbers? I don't know. What I know is that 1.7 and 1.8 always do the job. But not 1.9.

Big news! I have both LAN and WiFi on all my Macs (WiFi for lication on maps etc). I turned off WiFi on both both Macs and now the other Macs find a LAN'ed world from one of the Macs!!!!
So - it's solved...though it's still a "bug" 'cause of course one should be able to have both LAN and WiFi on and that's no problem with MC 1.7 and MC 1.8.
So - when both LAN and WiFi connection of computers - at least Macs - the port scanning in MC is broken.

Is the implication that the Minecraft JVM isn't scanning all active network interfaces, just whatever one it deems (apparently incorrectly in many cases) to be the primary?

same issue, here are my details

---- Minecraft Crash Report ----
// But it works on my machine.

Time: 4/24/16 5:09 PM
Description: Manually triggered debug crash

java.lang.Throwable
	at bcf.az(SourceFile:1694)
	at bcf.t(SourceFile:1615)
	at bcf.av(SourceFile:962)
	at bcf.a(SourceFile:392)
	at net.minecraft.client.main.Main.main(SourceFile:124)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
	at bcf.az(SourceFile:1694)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bmt['notch_is_god'/1622, l='MpServer', x=-44.40, y=190.06, z=641.25]]
	Chunk stats: MultiplayerChunkCache: 441, 441
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (0,162,0), Chunk: (at 0,10,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 6558313 game time, 18000 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: adventure (ID 2). Hardcore: false. Cheats: false
	Forced entities: 1 total; [bmt['notch_is_god'/1622, l='MpServer', x=-44.40, y=190.06, z=641.25]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bku.a(SourceFile:365)
	at bcf.b(SourceFile:2515)
	at bcf.a(SourceFile:401)
	at net.minecraft.client.main.Main.main(SourceFile:124)

-- System Details --
Details:
	Minecraft Version: 1.9
	Operating System: Mac OS X (x86_64) version 10.11.4
	Java Version: 1.8.0_74, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 3440600256 bytes (3281 MB) / 4231266304 bytes (4035 MB) up to 4231266304 bytes (4035 MB)
	JVM Flags: 7 total; -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M -Xmx4048M -Xms4048M
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 1.9
	LWJGL: 2.9.2
	OpenGL: Intel(R) Iris(TM) Graphics 6100 GL version 2.1 INTEL-10.14.58, Intel Inc.
	GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because ARB_framebuffer_object is supported and separate blending is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

	Using VBOs: No
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: faithful32pack.zip (incompatible), Faithful 1.9 - 16w03a.zip
	Current Language: English (US)
	Profiler Position: N/A (disabled)
	CPU: 4x Intel(R) Core(TM) i5-5257U CPU @ 2.70GHz

direct connect does not work for me, says its trying, then gives up

Then its a different issue, possibly firewall or incorrect configuration of your router. This ticket is specifically about the LAN list not working.

This is still an issue in 1.10.

Is this still an issue in the latest snapshot 16w44a? If so please update the affected versions.

This is an automated comment on any open or reopened issue with out-of-date affected versions.

Yes, this is still an issue in 16w44a. I do not have permission to update the versions affected, or I would do so.

If both Macs are ONLY on wired LAN = OK. If one or both Macs also have WiFi on = issue occurs.

Has there been a resolution for this issue yet?

When using Minecraft 1.9 or later (1.10, 1.11) on any version of Mac OSX, Open to LAN yields no results when Scanning for games on local network.

This happens ONLY on WIFI, when all Mac computers wired on ethernet, LAN servers can be found.

Works on all versions of Minecraft 1.8.9 and earlier.

Direct Connect works.

I have tried:

• quitting and restarting Minecraft

• restarting computer

• power cycling modem and router

• re-installing Minecraft on all computers.

• Confirmed Firewall is OFF

• turned firewall ON on all computers and then turned OFF

• restarted all computers again

• all this, no love

I have spent hours searching the internet for a solution and have only found the Direct Connect option. This is not practical as each time the user opens the single player game to LAN, the Port changes. So even if the IPv4 address is static, new information has to be provided to every other player each time the fame is restarted.

There are two reasons I can think of that wifi would matter:

(1) If the Mac has multiple NICs, then the discovery system is tying its broadcasts to a specific NIC, which means they're not going out in the first place on wifi.
(2) If the response (UDP I assume again) is somehow not being sent out on the NIC it came in on, meaning that the response is bound to an unconnected NIC, so the packet is being thrown away.

I've written discovery services before. It's not hard. I've even had to design one to ensure that the response went out on the same NIC it came in on for purposes of fail over when both NICs were on the same subnet. This required that I bind a listener to each NIC (separately for eth0, eth1 on Linux), but that was a special case, and in general, the NIC and subset don't need to be considered, because the OS will route a datagram to the NIC set up for the IP address of the recipient. (My point is that I know that a listening port CAN be bound to a specific NIC, and I know that this is not the default situation, and it was much harder than the normal thing to do.)

For the protocols I developed, they were all client-initiated. The clients (written in Java, BTW) would send out broadcasts (to 255.255.255.255). The datagrams included source IP address (implicitly) and the port number on which the client is listening. This would get picked up by the servers, which would respond by sending a datagram back directly to the client specifically (single recipient) at the requested port. Macs were involved in this testing, and although I didn't test this intentionally, I have done so with both wifi and wired ethernet.

So other than some kind of weird decision to bind a UDP transmission of listening port to a specific NIC, rather than a specific subnet, I can't imagine why Minecraft is having this problem. I simply never ran into this kind of problem.

Without knowing if Minecraft uses server-initiated discovery or client-initiated discovery, I can't speculate further. Someone more experienced with wireshark could tell us.

The bug can be fixed by adding "-Djava.net.preferIPv4Stack=true" to your JVM arguments in the launcher.

I tried Greg's recommendation but can't seem to get this working either.
I can direct connect just fine, but I have to specify ip:port, my kids aren't going to be able to do that 😞. I've made sure that we are on the same network and Wifi band (both are on the 2.4 band). I would suspect the ability to direct connect negates any basic networking issues.

How does Minecraft broadcast a game? I can run a network trace and see what is happening.

Edit: Just grabbed a network capture and while Minecraft had a LAN enabled game running, the hosting PC sends out over UDP 64445 to 4445, to multicast address 224.0.2.60. This is received by my other PC, but still nothing shows in the games list.

I have a Netgear R7000 and both PCs are Windows 10, Minecraft versions are the same - 1.12.2

I tried the JVM arguments fix but it still doesn't work for me. I can't even get a direct connection to work. It times out. I am trying to connect Mac OS 10.11.6 to Mac OS 10.13.2 on wifi through a Motorola router. Using Minecraft version 1.12.2

i can confirm: this is completely broken. Mac server, windows 10 client, both connected to dumb 100BASE-TX hub. mac firewall is ON. windows defender firewall is OFF, network type is 'private'. PC can connect to mac OK with 'Direct Connect' host:port, but game does NOT appear in 'Scanning' list. both Minecraft 1.12.2

In my experience the issue is caused by having multiple network interfaces either on hosting or on client side. Minecraft apparently transmits/listens to UDP broadcasts only on one of the available network interfaces, based on wireshark captures. If you want to make sure that the two (or more) computers can see each other, disable the unneeded interfaces temporarily before launching the game.

I hope, that this workaround can help you out until the issue is fixed.

Affects 18w22c

I think this one just needs someone to take a look at the logic on how the LAN list gets populated. In all cases I've seen where the multicast traffic is actually getting to the client, the only time the game doesn't show up is when there's other network interfaces (or ipv6 interfaces) involved. True you could disable them, but people have legitimate needs for multiple interfaces (Wifi/wired docking stations, VPN interfaces, etc). So maybe the best way is to just listen for 224.0.2.60:4445 announcements on all available (or up) interfaces.

This has been an issue for quite some time (since 1.8 I believe) and will affect most OSX users by default because of the way ipv6 is enabled by default (which is why you need the JVM options). But even with those options enabled, you can still run into issues if you have multiple interfaces (like me).

The core of the problem is that the game seems to just pick some arbitrary interface to listen on, and if the announcement doesn't come in via that specific interface, then it's no dice.

I have three Macs and none of them can play a LAN game out of the box.

For each computer and for each Minecraft version (e.g. snapshot versus latest) we must go into the launch options and configure -Djava.net.preferIPv4Stack=true

I've outlined my struggles with this process here: https://gaming.stackexchange.com/a/320864/199492

At the time of writing this, it has 10 upvotes, so this fix is very important for the Java Edition on Mac to be usable.

But that's the good news.  The bad news is that I've recently purchased a 2017 MacBook and the above workaround has stopped functioning.  I believe it's due to this bug MC-98598.

In all cases I've seen where the multicast traffic is actually getting to the client, the only time the game doesn't show up is when there's other network interfaces (or ipv6 interfaces) involved. True you could disable them, but people have legitimate needs for multiple interfaces (Wifi/wired docking stations, VPN interfaces, etc). So maybe the best way is to just listen for 224.0.2.60:4445 announcements on all available (or up) interfaces.

This is my fear... The MacBook pro appears to ship with iBridge interface (en5 on my machine) and I have a feeling it's conflicting as I've done all of the standard troubleshooting that's worked on the other Macs.  Interestingly enough, this en5 has no option to disable.  A reddit forum states it's used for the touch-bar and keyboard, so forcing it off may be a bad idea anyway.  https://www.reddit.com/r/MacOS/comments/8bzk6k

I determined iBridge using the following command:

cat /Library/Preferences/SystemConfiguration/NetworkInterfaces.plist | grep en5

Which returns (scroll to the far right to see iBridge)

<string>en5</string>
			<string>IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/XHC1@14/XHC1@14000000/HS03@14100000/iBridge@14100000/NCM Data@5/AppleUSBNCMData/en5</string>

Direct connection technically works as a viable workaround but it's not a practical workaround since the server port changes each time we fire up a LAN game.

Perhaps some logic could be added to try to locate the "internet" interface?  https://stackoverflow.com/questions/8462498

I'm very interested in seeing this bug to completion and if needed, offering testing and debug logs to the developers.

There is another possible workaround for this problem: explicitly specify which network interface the system should use for multicast. Under linux, just add a route for network 224.0.0.0/4 with the following command:

route add -net 224.0.0.0 netmask 240.0.0.0 dev interface_name

where interface_name is the name of the network interface to use for multicast traffic.

Under windows, change the metric of the interface in question to the lowest value among all of them. Open the Advanced TCP/IP settings dialog under IPv4 settings of the interface, uncheck automatic metric, then enter 1 for interface metric. The value of 1 will beat every other interfaces with automatic metric enabled, because the lowest value assigned automatically is 5.

I hope that this little tweaking resolves your problems.

The issue is not that the Mac looking to join isn't receiving the multicast traffic. In all cases, the multicast traffic gets to the client on the correct interface. It's the application that's not listening for it on the correct interface.

Gábor,

I tried your solution to add the default route for multicast, and it didn't seem to help.  For Mac the commands were:

sudo route delete 224.0.0/4
sudo route add -net 224.0.0.0 -netmask 240.0.0.0 -device en0

But it does not fix the problem for the one client – MacBook Pro – that fails to see the Minecraft LAN server.  The MacBook Air (with IPv4 workaround) and Windows 10 Dell XPS can connect but the MacBook pro cannot unless it is using the direct connect option. 

There are no solutions posted here that will work reliably. Gábor's solution will not work because it's not a problem with the network stack. The Java arguments will work as long as you don't have any other valid ipv4 interfaces that the minecraft application will choose (i.e. VPN interfaces).

My suspicion (as I've posted 3 times already), is that the minecraft application picks an arbitrary interface to listen for the multicast traffic on, but that is not always the interface the traffic arrives at. This is an application issue. If we knew what logic the application was using to pick the interface, we could come up with a workaround, but it doesn't seem that anyone with access to the source code is interested in looking at this painful regression that has existed since 1.9 was released.

IN ALL CASES, you can see the traffic arrive at your PC by running:

sudo tcpdump -A -n host 224.0.2.60

This will output something like this if another client is announcing a LAN game:

11:13:07.739601 IP 10.88.88.88.53383 > 224.0.2.60.4445: UDP, length 61
..^..<..@.-...E..Y........
Ed,...<...].E..[MOTD]Fire*** - ultimate survival[/MOTD][AD]59973[/AD]
^C

 This is proof that the traffic arrives at the network stack, it's just not processed by minecraft.

By the way, this is the technique I use when I want to use my Mac to connect to my kids LAN worlds using direct connect option. The number between the — [AD] /AD tags is the port. The IP is the source IP of the UDP packet (So in the above example you'd type in — 10.88.88.88:59973 for direct connect). But if it's your kid who has the Mac, good luck with that. They'll probably get frustrated and just play fortnite instead 😉

Still an issue in 19w06a

gs007, thank you. You finally pointed me in the right direction to fix this issue. Namely, I had several IPv4 network interfaces on my Win10 machine due to having things like Docker for Windows and Virtual Box installed. Disabling those network interfaces so that I only had a single IPv4 network interface left finally worked.

It definitely seems to be the case that the application simply ends up listening on the wrong interface

This issue also occurs on Windows when the computer has multiple active network interfaces. Minecraft chooses the interface with the highest priority (a.k.a. lowest metric). There are tools to change interface priorities, but the game should offer a list of interfaces to bind to. Non-technical users are stuck and must use "direct connect" which is not as easy as discovery.

> There are tools to change interface priorities

Can you provide some information on this? MacBook Pro with touchbar can't see lan about 50% of the time.

@Tres

I'm not sure there will be much you can do on your mac to reliably populate the game list until this bug is addressed by a developer. You can eliminate your wireless, network stack setup, etc, as the problem by running the tcpdump command above on the mac that wants to join the game. If you get an output showing the LAN announcement, your setup is fine. If you only use one interface for 'regular networking' i.e., you don't have any VPN interfaces, don't use virtualization software like VMware or Virtualbox, you may be able to solve it by:

Disabling the ipv6 on your interface at the OSX level:

List interfaces:

networksetup -listallnetworkservices

then (Let's say your interface is 'Wi-Fi' like most), turn off ipv6:{{}}

networksetup -setv6off Wi-Fi

Then you would have to make sure the interface you want is on the top of the priority list in the sidebar of Settings > Network (which looks like the below):

You can also do this with a Java option in the minecraft launcher or by modifying parameters for Java on your system framework directly. Both are a pain for various reasons and are outlined in detail here.

For what it's worth, I've tried to figure it out on mac-- messing with interface priority, etc, but there doesn't seem to be a consistent correlation where I can this working. I believe there is a logic, I just can't figure it out experimentally.

I am a network guy, not a developer. I've researched all network centric approaches, but the simple answer is, that with OSX, the logic that was used to do this was broken (regression) around 1.8 and no one bothered to fix it. To be fair, OSX has less marketshare, and the networking stack isn't the most fun to work with. I have issues with almost all vendors that develop cross platform networking solutions that include mac.

However, it's my personal opinion, that if an individual minecraft developer with the right knowledge were to look at this, it would be an extremely quick fix.

On the bright side, my kids know how to run a packet capture and understand networking now. I guess that's a positive.

Also note that in terms of open issues, this one only has 2 less votes than the top voted open issue on MC Java Edition. If we could get more votes to put it on top, perhaps this long lasting issue could be resolved.

Thanks. Yeah the problem as I understand it is the touchbar has it's own active network interface which increases the chances of the problem occuring.

For what it's worth, I've tried to figure it out on mac-- messing with interface priority, etc, but there doesn't seem to be a consistent correlation where I can this working. I believe there is a logic, I just can't figure it out experimentally.

I'm a Java developer, and finding the primary interface 99% of the time is as simple as reaching to an internet endpoint and binding to that NetworkInterface instance.

The fact that this is a regression is particularly frustrating as the Mojang team already has the working code available. 

If it's possible, I think a very sane approach/fix for java edition in general (since it's cross platform) is to just listen on all active network interfaces for multicast traffic. It's a very simple solution to a problem that has been around for a long time.

1.15.2 Pre-Release 2 is affected.

Many years ago this worked on old versions. Been broken for ages. My kids are used to entering an IP address and port number in direct connect ... so there is an educational aspect 😃

Adding "-Djava.net.preferIPv4Stack=true" to the command line arguments in the client only (not game serving) worked for me - it appeared in the multi-player games list.

All my Macs are Wi-Fi, and have been for years. Obviously most of them have Ethernet as well. My machine does not have Ethernet but I have got and used a thunderbolt Ethernet adapter, and ifconfig and System Preferences network list 14 different network interfaces.

My network does not have IPv6, but obviously like all modern operating systems, IPv6 is configured by default - even if it's just local link-local.

My Wi-Fi connection on all machines is at the top of the list. Disabling other networks or IPv6 machine wide is not an option for me - and I don't think it's a good idea. 

I note from above: "This issue also occurs on Windows when the computer has multiple active network interfaces."

Has affected me since 1.15. Haven't played MC since then

I can confirm: By disabling all active network interfaces (except the current using one) on Windows, Minecraft will be able to discover local worlds. (at least on my case)

Disabling everything except for my primary interface and Bluetooth interface made Minecraft immediately recognize the open LAN game.

For a scanning tool meant to make LAN games more convenient to join, disabling all of my interfaces every time I want someone in my house to join my game is in no way convenient.

@gs007: I totally agree with you. This seems like it should be a really simple fix. As people have started using VPNs or Hamachi more regularly, Minecraft shouldn't be selecting a single interface to broadcast (or listen) on. I too remember having no issues with LANs automatically showing up in the server browser pre-1.9.

Having this issue on PC to PC connection.

Tried all of the above suggestions by others on the thread, but nothing allows me to connect to the other computer on same network. We tried connecting both directions. I can see the game from one computer but can't see it from the other computer.

This is only affecting us when we are on 1.17.1. We tried on 1.16.5 and it connected immediately. Unfortunately, the school project I am trying to help with is a 1.17.1 map.

I have just moved myself and my son over to Java edition and have the same issue as above on 1.17.1

I was able to access LAN easily on Bedrock even my 4yo could do it. 

But we are not able to see our world's in the LAN list. 

We can use IP/Port Direct Connection, but this is not viable for my son and daughter to do by themselves. 

Some quick stats on this issue:

• Just under 40 duplicate issues opened for this issue over 7 years. 

• The first mention of this bug was in 2015.

• It's still 9th on the list of issues people most want fixed by vote for MC Java Edition. After 7 years that's pretty impressive.

• Last version of MC Java that worked: 1.8

The solution is really simple: Have minecraft java app listen for multicast on ALL interfaces on the client. If you do that it will work.

As a note to bugfix PMs: Maybe 7 years open and reliably in top ten issues users vote on is enough to get the priority raised and have it assigned for a fix. I'm not saying there aren't more important issues out there, but this one keeps slipping through the cracks.