Certain chat messages exceed 32767 byte limit and disconnect clients

Can't reproduce in 14w08a.

Can still reproduce in 08a

No longer able to duplicate this issue. Closing as fixed.

Still in 14w21b:

Server

[22:42:11] [Server thread/INFO]: Starting minecraft server version 14w21b
...
[22:43:55] [Server thread/INFO]: [Kumasasa] Kumasasa, item.item.bone, item.item.arrow, Skeleton, Cow, Chicken, Pig, Cow,
 entity.MinecartRideable.name, Pig, Pig, Chicken, Chicken, item.item.bone, item.item.arrow, Chicken, Sheep, Chicken, Pig
, Cow, Cow, Chicken, Chicken, Chicken, Chicken, Pig, Cow, Cow, item.item.egg, Chicken, item.item.egg, Zombie, Chicken, S
quid, Slime, Cow, Zombie, Chicken, Cow, Sheep, Bat, Chicken, item.item.chickenRaw, Chicken, Pig, item.item.feather, Chic
ken, item.item.egg, Skeleton, Pig, Skeleton, Chicken, Pig, Cow, Chicken, item.item.egg, Cow, Cow, Cow, Cow, item.item.eg
g, Chicken, Cow, Spider, Cow, Chicken, Chicken, Pig, Chicken, Zombie, Cow, Pig, Slime, Cow, Cow, Chicken, item.item.egg,
 Creeper, Skeleton, Cow, Chicken, Cow, Zombie, Chicken, Pig, Pig, Cow, Pig, Pig, Chicken, Cow, Chicken, Bat, Chicken, it
em.item.rottenFlesh, Chicken, Pig, Chicken, Sheep, Pig, Chicken, Cow, item.item.egg, Chicken, Chicken, Skeleton, item.it
em.feather, item.item.chickenRaw, Sheep, Pig, Chicken, Cow, Chicken, Cow, Cow, Cow, Cow, Sheep, Pig, Pig, Chicken, Pig,
item.item.egg, Chicken, Pig, Pig, Chicken, Cow, Chicken, Bat, Pig, Chicken, Bat, Squid, Cow, Skeleton, Zombie, Chicken,
Creeper, Chicken, Cow, Pig, Chicken, Pig, Witch, Chicken, Chicken, Cow, Cow, Pig, Pig, item.item.arrow, Pig, Squid, Pig,
 item.item.bone, item.item.egg, Chicken, Pig, Chicken, Chicken, item.item.egg, Bat, Pig, item.item.egg, Pig, Cow, item.i
tem.bone, Skeleton, Cow, Pig, Cow, Cow, Pig, Cow, Zombie, Chicken, Zombie, Cow, Chicken, Skeleton, Cow, item.item.rotten
Flesh, item.item.arrow, Chicken, Chicken, Chicken, Skeleton, Pig, Cow, item.item.bone, Sheep, Zombie, Sheep, Chicken, Ch
icken, Creeper, Chicken, Zombie, Bat, Pig, Cow, Bat, Pig, Pig, Pig, Pig, Pig, Zombie, Enderman, Pig, Cow, Chicken, Pig,
Cow, Skeleton, Skeleton, Pig, Pig, Cow, Chicken, Chicken, Creeper, Chicken, Creeper, Cow, Cow, Sheep, Chicken, Zombie, Z
ombie, Zombie, Chicken, Pig, Skeleton, Bat, Cow, Pig, Pig, Chicken, Skeleton, Pig, Chicken, Bat, Squid, Pig, Bat, Cow, S
quid, Squid, Chicken, Chicken, Chicken, Bat, item.item.egg, Cow, Skeleton, Creeper, Zombie, Chicken, Skeleton, Creeper,
item.item.egg, Zombie, Cow, Chicken, Cow, Zombie, Bat, Cow, Cow, Chicken, Bat, Creeper, Pig, Creeper, Chicken, Pig, Pig,
 Cow, Chicken, Spider, Cow, Skeleton, Creeper, Chicken, Zombie, Creeper, Creeper, Chicken, Pig, Chicken, item.item.dyePo
wder.black, Skeleton, Chicken, Creeper, Pig, Skeleton, Skeleton, Creeper, Creeper, Cow, Creeper, Pig, Skeleton, Creeper,
 Bat, Cow, Skeleton, Creeper, Bat, Creeper, Cow, Pig, Creeper, Chicken, Sheep, Chicken, Creeper, Skeleton, Skeleton, Chi
cken, item.item.egg, Skeleton, Bat, Cow, Cow, Cow, Sheep, Spider, Cow, Skeleton, Pig, Pig, Cow, Zombie, Cow, Chicken, Sk
eleton, Pig, Pig, Pig, Chicken, Chicken, Cow, Chicken, Cow, Chicken, Sheep, Sheep, Chicken, Chicken, Cow, Chicken, Pig,
Cow, Sheep, Cow, Pig, Pig, Chicken, Cow, Pig, Chicken, Cow, Cow, Cow, Cow, Chicken, Cow, Cow, Pig, Chicken, Sheep, Pig,
Pig, Cow, Chicken, Cow, Pig, Chicken, Chicken, Cow, Pig, Pig, Pig, Pig, arrow, Pig, Cow, Cow, Pig, Pig, Cow, Cow, Chicke
n, Cow, Chicken, Pig, Cow, Cow, Pig, Cow, Chicken, Sheep, Pig, Sheep, Cow, Pig, Chicken, Pig, Chicken, Cow, Chicken, Cow
, Pig, item.item.egg, Cow, Chicken, Chicken, Pig, Pig, Cow, Pig, Sheep, Cow, Chicken, Pig, Sheep, Pig, Cow, Chicken, ite
m.item.egg, Cow, Chicken, Sheep, Cow, item.item.leather, Pig, Pig, item.item.beefRaw, Chicken, Cow, Cow, Cow, Pig, Cow,
Chicken, Cow, Sheep, Pig, Pig, Pig, Cow, Pig, Pig, Cow, Cow, Sheep, Pig, Cow, item.item.egg, Cow, Cow, Chicken, Cow, Pig
, Pig, Chicken, Pig, Chicken, Cow, Cow, Chicken, Pig, Cow, Pig, Pig, Cow, Cow, item.item.egg, Pig, Cow, Cow, item.item.e
gg, Chicken, item.item.egg, Cow, Chicken, Cow, Cow, Chicken, Chicken, item.item.egg, Chicken, Pig, Cow, Chicken, Sheep,
Cow, Chicken, Cow, Cow, Cow, Cow, Pig, Cow, Chicken, Chicken, Pig, Chicken, Cow, Pig, Pig, Sheep, Pig, Pig, item.item.eg
g, Cow, Chicken, Pig, Cow, Chicken, Chicken, Chicken, Chicken, Cow, item.item.egg, Cow, Sheep, Cow, Cow, Cow, Sheep, Pig
, Cow, Pig, Chicken, Pig, Pig, Cow, Pig, Pig, Cow, Cow, item.item.egg, Chicken, Chicken, Cow, Cow, Cow, Pig, Chicken, Ch
icken, item.item.egg, Chicken, Chicken, Chicken, Cow, Pig, Cow, Cow and Cow
[22:43:55] [Netty IO #2/ERROR]: java.io.IOException: String too big (was 111997 bytes encoded, max 32767)
[22:43:55] [Server thread/INFO]: Kumasasa lost connection: TextComponent{text='Disconnected', siblings=[], style=Style{h
asParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null,
insertion=null}}
[22:43:55] [Server thread/INFO]: Kumasasa left the game

Client see screenshot.

Confirmed for 1.8pre2

The description of this bug is actually incorrect, because /say @e is not broken. The reason it kicks you is that there are so many entities that the text becomes too long to display in one chat message. Anything with an output of varying length could technically cause this. That's why it would be better to change the description of this bug to "Messages of more than 32767 characters kick the player".

A more appropriate title/description would be "Certain chat messages exceed 32767 character limit and disconnect clients."

15w49b

[16:18:22] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 2953ms behind, skipping 59 tick(s)
[16:19:14] [Server thread/INFO]: [Kumasasa] Horse, Horse, Horse, Horse, Kumasasa, Horse, Horse, Donkey, Horse, Horse, Horse, Horse, Horse, Horse, Hors
e, Horse, Horse, Horse, Horse, Horse, Horse, Horse, Horse, Horse, Horse, Horse, Horse, Donkey, Horse, Horse, Horse, Horse, Horse, Horse, Horse, Horse,
...
on, Squid, Bat, Skeleton, Skeleton, Squid, Sheep, Sheep, Spider, Skeleton, Sheep, Skeleton, Zombie, Zombie, Skeleton, Creeper, Skeleton, Creeper, Skel
eton, Squid, Zombie, Zombie, Squid, Squid, Sheep, Bat, Skeleton, Zombie, item.item.rottenFlesh, Witch, Bat, item.item.rottenFlesh, Bat, Bat, item.item
.bone, Creeper, item.item.arrow, Bat, Bat, Spider, Creeper, Creeper, Cow, Bat, Bat, Bat, Creeper, Enderman, Zombie, Skeleton, Creeper, Skeleton, Spide
r, Creeper, Sheep, Bat, Zombie, Creeper, item.item.egg, item.item.egg, Rabbit, Rabbit, Rabbit, Rabbit, item.item.seeds, item.tile.flower2.oxeyeDaisy,
Rabbit, Rabbit, Rabbit, item.item.seeds, item.item.seeds and item.item.seeds
[16:19:14] [Netty Server IO #2/ERROR]: io.netty.handler.codec.EncoderException: String too big (was 82327 bytes encoded, max 32767)
[16:19:14] [Server thread/INFO]: Kumasasa lost connection: TextComponent{text='Disconnected', siblings=[], style=Style{hasParent=false, color=null, bo
ld=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}
[16:19:14] [Server thread/INFO]: Kumasasa left the game

Confirmed for 15w51b. Simple to reproduce: spawn 128 heavy weighted pressure plate items.

15w51b MP console log

[18:23:13] [Server thread/INFO]: [__null] __null, item.tile.weightedPlate_heavy, item.tile.weightedPlate_heavy, item.tile.weightedPlate_heavy, [...], item.tile.weightedPlate_heavy and item.tile.weightedPlate_heavy
[18:23:13] [Netty Server IO #3/ERROR]: io.netty.handler.codec.EncoderException: String too big (was 34076 bytes encoded, max 32767)
[18:23:13] [Server thread/INFO]: __null lost connection: TextComponent{text='Disconnected', siblings=[], style=Style{hasParent=false, color=null, bold=null, italic=null, underlined=null, obfuscated=null, clickEvent=null, hoverEvent=null, insertion=null}}
[18:23:13] [Server thread/INFO]: __null left the game

Confirmed for 16w02a.

Confirmed for 1.9.1-pre3.

/say @e @e @e @e @e ... with just a few entities in the world.

Summary should be changed to "Certain chat messages exceed 32767 byte limit", because the data needs to be 32767 bytes, not characters.

Please link to this comment in the description

The following is based on decompiled version of Minecraft 1.9 using MCP 9.24 beta. All method and class names are the names used in the decompiled version.

The problem is that the server is sending invalid packets. The method net.minecraft.network.NettyPacketEncoder.encode(ChannelHandlerContext, Packet<?>, ByteBuf) fails writing the packet data to the PacketBuffer, it prints the error message (in this case "String too big (was [X] bytes encoded, max 32767)") but sends the packet anyways. The packet contains now only the packet id. When the client tries to read the String from the packet it fails. I do not know how to prevent the server from sending the packet, however the client can probably catch exceptions which are thrown when the method net.minecraft.network.NettyPacketDecoder.decode(ChannelHandlerContext, ByteBuf, List<Object>) calls the method net.minecraft.network.Packet.readPacketData(PacketBuffer) and not add the packet to this list (which might contain read packets).

protected void decode(ChannelHandlerContext p_decode_1_, ByteBuf p_decode_2_, List<Object> p_decode_3_) throws IOException, InstantiationException, IllegalAccessException, Exception
{
    if (p_decode_2_.readableBytes() != 0)
    {
        PacketBuffer packetbuffer = new PacketBuffer(p_decode_2_);
        int i = packetbuffer.readVarIntFromBuffer();
        Packet<?> packet = ((EnumConnectionState)p_decode_1_.channel().attr(NetworkManager.attrKeyConnectionState).get()).getPacket(this.direction, i);

        if (packet == null)
        {
            throw new IOException("Bad packet id " + i);
        }
        else
        {
            // Replaced this
            //packet.readPacketData(packetbuffer);
            try {
                packet.readPacketData(packetbuffer);
            }
            catch (Exception exception) {
                logger.error(exception);
                return;
            }

            if (packetbuffer.readableBytes() > 0)
            {
                throw new IOException("Packet " + ((EnumConnectionState)p_decode_1_.channel().attr(NetworkManager.attrKeyConnectionState).get()).getId() + "/" + i + " (" + packet.getClass().getSimpleName() + ") was larger than I expected, found " + packetbuffer.readableBytes() + " bytes extra whilst reading packet " + i);
            }
            else
            {
                p_decode_3_.add(packet);

                if (logger.isDebugEnabled())
                {
                    logger.debug(RECEIVED_PACKET_MARKER, " IN: [{}:{}] {}", new Object[] {p_decode_1_.channel().attr(NetworkManager.attrKeyConnectionState).get(), Integer.valueOf(i), packet.getClass().getName()});
                }
            }
        }
    }
}

Confirmed for 1.9.3-pre3.

Confirmed for 1.9.4.

Confirmed for 16w20a.

Confirmed for 16w21a.

Confirmed for 16w21b.

Confirmed for 1.10-pre1.

Confirmed for 1.10-pre2.

Confirmed for 1.10.