java.lang.NullPointerException: Cannot invoke "java.lang.CharSequence.length()" because "seq" is null

[SpigotRCE]

java.lang.NullPointerException: Cannot invoke "java.lang.CharSequence.length()" because "seq" is null
at io.netty.buffer.ByteBufUtil.utf8Bytes(ByteBufUtil.java:1103) ~[velocity.jar:3.4.0-SNAPSHOT (git-99aaf3ce-b439)]
at ua.nanit.limbo.protocol.ByteMessage.writeString(ByteMessage.java:98) ~[?:?]
at ua.nanit.limbo.protocol.packets.login.PacketLoginSuccess.encode(PacketLoginSuccess.java:48) ~[?:?]
at ua.nanit.limbo.protocol.PacketSnapshot.encode(PacketSnapshot.java:50) ~[?:?]
at ua.nanit.limbo.protocol.PacketSnapshot.of(PacketSnapshot.java:85) ~[?:?]
at ua.nanit.limbo.connection.PacketSnapshots.(PacketSnapshots.java:119) ~[?:?]
at ua.nanit.limbo.server.LimboServer.start(LimboServer.java:96) ~[?:?]
at org.nexuscraft.corevelocity.misc.LimboManager.createLimboServer(LimboManager.java:55) ~[?:?]
at org.nexuscraft.corevelocity.misc.ServerHandler.onLimboRequest(ServerHandler.java:42) ~[?:?]
at org.nexuscraft.corevelocity.listener.PlayerServerListener.onConnectionRequest(PlayerServerListener.java:51) ~[?:?]
at org.nexuscraft.corevelocity.listener.Lmbda$42.execute(Unknown Source) ~[?:?]
at com.velocitypowered.proxy.event.UntargetedEventHandler$VoidHandler.lambda$buildHandler$0(UntargetedEventHandler.java:56) ~[velocity.jar:3.4.0-SNAPSHOT (git-99aaf3ce-b439)]
at com.velocitypowered.proxy.event.VelocityEventManager.fire(VelocityEventManager.java:676) ~[velocity.jar:3.4.0-SNAPSHOT (git-99aaf3ce-b439)]
at com.velocitypowered.proxy.event.VelocityEventManager.lambda$fire$5(VelocityEventManager.java:541) ~[velocity.jar:3.4.0-SNAPSHOT (git-99aaf3ce-b439)]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144) ~[?:?]
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642) ~[?:?]
at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]

[Zffu]

what caused this error?

[bivashy]

1. Client version?
2. Is client modded (Fabric/Forge/NeoForge or anything else)
3. ViaVersion on proxy?
4. Steps to reproduce

[SpigotRCE]

1.21.1
Fabric
no
idk

when using the config it works fine but with API this happens

[bivashy]

Try with vanilla Minecraft, Fabric could be the cause of the bug.

[SpigotRCE]

I don't think so, I tried with vanilla too but didn't work, when creating a limbo from config, it works fine for both vanilla and fabric but not with the API

[SpigotRCE]

That's what I am asking

[bivashy]

Your config #getPingData()#getVersion() returns null.

It tries to write "username" into PacketLoginSuccess, see:

NanoLimboPlugin/api/src/main/java/ua/nanit/limbo/protocol/packets/login/PacketLoginSuccess.java

Line 48 in ed238e7

msg.writeString(username);

It writes null, but it should be declared here:

NanoLimboPlugin/api/src/main/java/ua/nanit/limbo/connection/PacketSnapshots.java

Line 91 in ed238e7

loginSuccess.setUsername(username);

[bivashy]

Solution: Config should declare username instead of simply returning new PingData()

[SpigotRCE]

Ok it worked, but what do I set in protocol version?

[bivashy]

I know that but how does it sets the protocol version if the limbo is created from the config?

https://github.com/bivashy/NanoLimboPlugin/blob/main/api/src/main/java/ua/nanit/limbo/protocol/packets/status/PacketStatusResponse.java

[SpigotRCE]

I have seen that but idk why it didn't work for me, I even tried to set the protocol version to the Player's protocol version but didn't work

[SpigotRCE]

any update?

[bivashy]

any update?

i don't have idea why it doesn't work, but you could try ask nan1t, or elsewhere

[SpigotRCE]

I legit don't know too, but if I do the same thing but with a config file, it works fine, maybe we can hop on discord and try fix this?

[SpigotRCE]

`package org.nexuscraft.corevelocity.misc;

import com.velocitypowered.api.proxy.ProxyServer;
import com.velocitypowered.api.proxy.server.ServerInfo;
import org.nexuscraft.corevelocity.Core;
import org.slf4j.Logger;
import ua.nanit.limbo.configuration.LimboConfig;
import ua.nanit.limbo.server.Command;
import ua.nanit.limbo.server.CommandHandler;
import ua.nanit.limbo.server.LimboServer;
import ua.nanit.limbo.server.data.BossBar;
import ua.nanit.limbo.server.data.InfoForwarding;
import ua.nanit.limbo.server.data.PingData;
import ua.nanit.limbo.server.data.Title;

import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Random;

public class LimboManager {
private final ProxyServer proxyServer;
private final Core plugin;
private final Logger logger;
private final HashMap<LimboServer, Integer> limboServers; // Limbo Instance, port number
private final Random random;

public LimboManager(ProxyServer proxyServer, Core plugin, Logger logger) {
    this.proxyServer = proxyServer;
    this.plugin = plugin;
    this.logger = logger;
    this.limboServers = new HashMap<>();
    this.random = new Random();

    logger.info("Started LimboManager");
}

public HashMap<LimboServer, Integer> getLimboServers() {
    return limboServers;
}

public LimboServer createLimboServer() {
    int port = 0;
    while (port == 0) {
        port = random.nextInt(65535) + 1024;
        if (!limboServers.containsValue(port) && port != 25565 && port != 19132) {
            break;
        }
    }

    LimboServer limboServer = new LimboServer(new Config("local-limbo-" + port, port), new CommandHandler_(), getClass().getClassLoader());
    limboServers.put(limboServer, port);
    try {
        limboServer.start();
    } catch (Exception e) {
        logger.error("Failed to start Limbo Server", e);
        return null;
    }
    proxyServer.registerServer(
            new ServerInfo("local-limbo-" + port,
                    (InetSocketAddress) limboServer.getConfig().getAddress()
            )
    );

    logger.info("Created Limbo Server: {}, on port {}", limboServer.getConfig().getBrandName(), port);
    return limboServer;
}

public void destroyLimboServer(LimboServer limboServer) {
    int port = limboServers.get(limboServer);
    limboServer.stop();
    limboServers.remove(limboServer);
    logger.info("Destroyed Limbo Server: {}, on port {}", limboServer.getConfig().getBrandName(), port);
}

private static class Config implements LimboConfig {
    private final String name;
    private final int port;
    private final InfoForwarding infoForwarding;
    private final PingData pingData;

    public Config(String name, int port) {
        this.name = name;
        this.port = port;
        this.infoForwarding = new InfoForwarding();
        this.pingData = new PingData();
        this.pingData.setDescription("NexusLimbo");
        this.pingData.setProtocol(-1);
        this.pingData.setVersion("1.0");
    }

    @Override
    public SocketAddress getAddress() {
        return new InetSocketAddress("0.0.0.0", port);
    }

    @Override
    public int getMaxPlayers() {
        return -1;
    }

    @Override
    public PingData getPingData() {
        return pingData;
    }

    @Override
    public String getDimensionType() {
        return "THE_END";
    }

    @Override
    public int getGameMode() {
        return 3;
    }

    @Override
    public InfoForwarding getInfoForwarding() {
        return infoForwarding;
    }

    @Override
    public long getReadTimeout() {
        return 30000;
    }

    @Override
    public int getDebugLevel() {
        return 0;
    }

    @Override
    public boolean isUseBrandName() {
        return true;
    }

    @Override
    public boolean isUseJoinMessage() {
        return false;
    }

    @Override
    public boolean isUseBossBar() {
        return false;
    }

    @Override
    public boolean isUseTitle() {
        return false;
    }

    @Override
    public boolean isUsePlayerList() {
        return false;
    }

    @Override
    public boolean isUseHeaderAndFooter() {
        return false;
    }

    @Override
    public String getBrandName() {
        return name;
    }

    @Override
    public String getJoinMessage() {
        return "";
    }

    @Override
    public BossBar getBossBar() {
        return null;
    }

    @Override
    public Title getTitle() {
        return null;
    }

    @Override
    public String getPlayerListUsername() {
        return "";
    }

    @Override
    public String getPlayerListHeader() {
        return "";
    }

    @Override
    public String getPlayerListFooter() {
        return "";
    }

    @Override
    public boolean isUseEpoll() {
        return true;
    }

    @Override
    public int getBossGroupSize() {
        return 1;
    }

    @Override
    public int getWorkerGroupSize() {
        return 4;
    }
}


private static class CommandHandler_ implements CommandHandler<Command> {
    @Override
    public Collection<Command> getCommands() {
        return List.of();
    }

    @Override
    public void register(Command command) {
    }

    @Override
    public boolean executeCommand(String s) {
        return false;
    }
}

}
`

`
public void onLimboRequest(Player player) {
LimboServer server = plugin.getLimboManager().createLimboServer();
if (server == null) {
player.disconnect(Component.text("Unable to create limbo server! (Very Bad)"));
return;
}

    server.getConfig().getPingData().setProtocol(player.getProtocolVersion().getProtocol());
    server.getConfig().getPingData().setVersion(player.getProtocolVersion().getVersionIntroducedIn());

    player.createConnectionRequest(proxyServer.getServer(server.getConfig().getBrandName()).get()).fireAndForget();
}
`

`
[17:55:57 ERROR]: [connected player] Milkthedev (ip): disconnected while connecting to local-limbo-19257: Unsupported client version
`