[Solved] Client-side event when joining a server

[Blackop778]

I want to send a packet to a server whenever I join it. What event should I subscribe to to know when to send the packet? It would be okay if it triggered while joining a single player world too.

 

I considered using an EntityJoinWorldEvent but I only want to trigger it for myself and not for loading other players (would that happen?).

Edited March 3, 2017 by Blackop778

[Draco18s]

What are you sending a packet for?

There's already an event on the server for when a player joins: why is that not sufficient?

[Choonster]

23 minutes ago, Blackop778 said:

I want to send a packet to a server whenever I join it. What event should I subscribe to to know when to send the packet? It would be okay if it triggered while joining a single player world too.

 

Try using FMLNetworkEvent.ClientConnectedToServerEvent. Keep in mind that this is fired on a network thread rather than the main thread, so you need to schedule a task to run on the main thread before you can safely interact with normal Minecraft classes.

 

I'm not entirely sure whether a SimpleNetworkWrapper can be safely used from multiple threads at once.

 

Quote

I considered using an EntityJoinWorldEvent but I only want to trigger it for myself and not for loading other players (would that happen?).

 

You could check that the event's entity is the client player before sending the packet.

[Blackop778]

18 minutes ago, Draco18s said:

What are you sending a packet for?

There's already an event on the server for when a player joins: why is that not sufficient?

 

[Blackop778]

50 minutes ago, Choonster said:

 

Try using FMLNetworkEvent.ClientConnectedToServerEvent. Keep in mind that this is fired on a network thread rather than the main thread, so you need to schedule a task to run on the main thread before you can safely interact with normal Minecraft classes.

 

I'm not entirely sure whether a SimpleNetworkWrapper can be safely used from multiple threads at once.

 

 

You could check that the event's entity is the client player before sending the packet.

Using the code:

@SubscribeEvent
    public void onPlayerJoinedServer(FMLNetworkEvent.ClientConnectedToServerEvent event) {
	Minecraft.getMinecraft().addScheduledTask(new Runnable() {
	    @Override
	    public void run() {
		NETWORKWRAPPER.sendToServer(new HasModMessage());
		MineCalc.LOGGER.info("Joined a server");
	    }
	});
    }

The Logger works but the message never gets received on the server. When I left the server an error is thrown in the client:

Spoiler

[23:59:52] [Client thread/FATAL]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NullPointerException
	at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_121]
	at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_121]
	at net.minecraft.util.Util.runTask(Util.java:26) [Util.class:?]
	at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:1108) [Minecraft.class:?]
	at net.minecraft.client.Minecraft.run(Minecraft.java:406) [Minecraft.class:?]
	at net.minecraft.client.main.Main.main(Main.java:118) [Main.class:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_121]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_121]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_121]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_121]
	at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
	at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_121]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_121]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_121]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_121]
	at net.minecraftforge.gradle.GradleStartCommon.launch(GradleStartCommon.java:97) [start/:?]
	at GradleStart.main(GradleStart.java:26) [start/:?]
Caused by: java.lang.NullPointerException
	at net.minecraft.network.play.server.SPacketEntityStatus.getEntity(SPacketEntityStatus.java:56) ~[SPacketEntityStatus.class:?]
	at net.minecraft.client.network.NetHandlerPlayClient.handleEntityStatus(NetHandlerPlayClient.java:1082) ~[NetHandlerPlayClient.class:?]
	at net.minecraft.network.play.server.SPacketEntityStatus.processPacket(SPacketEntityStatus.java:50) ~[SPacketEntityStatus.class:?]
	at net.minecraft.network.play.server.SPacketEntityStatus.processPacket(SPacketEntityStatus.java:12) ~[SPacketEntityStatus.class:?]
	at net.minecraft.network.PacketThreadUtil$1.run(PacketThreadUtil.java:15) ~[PacketThreadUtil$1.class:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_121]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_121]
	at net.minecraft.util.Util.runTask(Util.java:25) ~[Util.class:?]
	... 15 more

 

 

Edited March 2, 2017 by Blackop778

[Choonster]

It looks like FMLNetworkEvent.ClientConnectedToServerEvent may be too early to send packets, so you should probably use EntityJoinWorldEvent instead.

 

 

19 minutes ago, Blackop778 said:

Caused by: java.lang.NullPointerException
	at net.minecraft.network.play.server.SPacketEntityStatus.getEntity(SPacketEntityStatus.java:56) ~[SPacketEntityStatus.class:?]
	at net.minecraft.client.network.NetHandlerPlayClient.handleEntityStatus(NetHandlerPlayClient.java:1082) ~[NetHandlerPlayClient.class:?]
	at net.minecraft.network.play.server.SPacketEntityStatus.processPacket(SPacketEntityStatus.java:50) ~[SPacketEntityStatus.class:?]
	at net.minecraft.network.play.server.SPacketEntityStatus.processPacket(SPacketEntityStatus.java:12) ~[SPacketEntityStatus.class:?]

 

 

Something is sending an SPacketEntityStatus when there's no client World. Set a breakpoint in the SPacketEntityStatus(Entity, byte) constructor to see where the packet is being sent from.

[Blackop778]

Works great using EntityJoinWorldEvent. I also had that event unregister itself to reduce computation (probably by a minuscule amount) and added it back with 

@SubscribeEvent
    public void onPlayerLeftServer(ClientDisconnectionFromServerEvent event) {
	Minecraft.getMinecraft().addScheduledTask(new Runnable() {
	    @Override
	    public void run() {
		MinecraftForge.EVENT_BUS.register(new ClassThatContainsEntityJoinWorldEventMethod());
	    }
	});
    }