Eric Golde – How to code a Minecraft PVP Client: Episode #19.2: Bukkit Communication – Server side packets!

Hello guys it is Eric here again um a little bit of time to make a video so in this video I’m going to be going over How to kind of write the base bucket plugin for sending packet and then next couple videos I’ll go over more in this but this is mainly just how to get the hello world packet we made last time to be sent from the client to the server from the server to the client sorry

How many join the server yeah um this is known could be like a bucket – I mean it is bucket but I’m not gonna die going into depth of bucket that’s yeah this is gonna be a very simple overview of bucket and more until like here’s how we

Register a packet of all that jazz and the framework for that first you’re gonna want download spigot 1.8 we need in protocol Lib you could use bucket if you want but I’m gonna use bigot since I already have it on me then we’re gonna need protocol and make sure you get the

One for 1.8 there’s different versions of it I’m just gonna make a new folder let’s call it server because I can’t come up with a better name both these in here and what I’m gonna do is make a new folder we’re going to call it plugins you already have a server

Setup you can track protocol it in there all good going to get a command prompt copy it oops I just need to say cb4 location run this and then it’s going to generate some files we need to agree to the EULA let’s do that real quick go

Back to here and again now we’re just going to just going to generate all the little files for us make a server probably if you already have a server for your client then just as I said put in the plugins folder but for those who don’t here’s overly simplified explanation of

Setting up a server well looks like an update for protocol or whatever yeah I’m using one pointy little bit out of date but that’s fine for this series um quote we have a server I’m gonna stop it for now since don’t need it this can really where

We’re gonna like test our plugin yeah now let’s actually go on to writing the plugin you probably can already tell I don’t have a script for this video so have time to write one really and I found some time on my roommates not here so yeah let’s call this example client

Plugin I don’t know so then what we want to do is right click say build path add external archives and we want to go to our folder which is minecraft or nowhere it’s just to my desktop called the server should have called their name and

We want to add spigot jar to it and then we also want to add our protocol lid plugin well not mine Norma downloading you gets a big package call what everyone let’s go just sample client dot server good good enough chirp it’s quite loop geez let’s quickly make main class file

And this is going to extend this note spell that rate at all import those alright now we’ve those imported just like every bucket plugin we’re gonna need our plugin yml so let’s make a new file we’re going to call pluggin dot yml now and it’s gonna open

In place it just didn’t want to now you got to see some stuff for my website cool yeah okay we’re gonna need name I said it’s not an extensive bucket tutorial so just call it the example client-server example clay plugin good enough i mean is going to be where i mean is for

Example coins dot server about main cuz we call them family not java version 1.0 i think what i’ll start need for book it’s been a while since I’ve done bucket I think you need an author we might not need an author and there’s also the description PSCR I Pete description

Example client login that does stuff and then we also need to say depend DEP you need to say depend on protocol always mess the spelling about it there’s our plugin super simple no let’s just make sure this works by saying get loggers info hello world so its export our

Plugin make sure this actually runs we’re going to say Jenner or no say Java jar file make sure you’re exporting to plug-in and it has the plugin women don’t export your client that’s plugin that’s not yeah not a good good let’s just call this example clan server plugins good enough have good names

Games or things let’s run our server again and we should see prints hello world hopefully look at that hello world it worked first time without a script that makes me happy okay I’m gonna stop this anymore yeah what are they doing closing okay so sorry I feel like I’m rushing this but

The my roommate is out right now and I’m just trying to like get this kind of done you know so I’m gonna make a new package called packets and just like the client we’re gonna make one called ec packet I’m just gonna be the base class and we are going to say implements

Packet and then we’re gonna import net minecraft server now when I add the unimplemented method you’ll see they’re called a piece you know a a and B because the server is off you skated the functions in they’re all named a and B and stuff it’s you know it’s fine but

It’s not great when writing a plugin I feel like because I get confused well what’s the dead between a and B how do I know which one is right and read and all that stuff so I’m gonna make this abstract and I’m going to add a few functions this is the public abstract

Avoid read packet data it’s gonna have package data pack it data serializer call it data oh I forgot I’m stressed so I can’t do that all right I’m gonna want one that’s 4 write data or a great packet data and then I want another one called handle and it’s going to take

Packet listener let’s call it listener now i st listener all right I’m gonna move this up here just listen to me Listener and we’re just going to call read packet from a data rate packet handle as listener this way that it’s a little extra work but this way when we have like s hello world we can have the same name schemes as we do as we do

In the client to make it easier or at least from my brain at least to comprehend you can leave it as a and be more but I find it easier to do that way now what I want to do is excuse me make two packages server client just like

Last time any packets that are sent from server going here any packets that are sent from the client going there so we’re going to say s packet is going to extend EC packet and this is also gonna be abstract I need to slow down a minute whoo okay we’re gonna override handle

And we’re going to override read packet data no way it’s just advanced so for handle it’s and just a note for myself sent from servers will be getting won’t be getting messages back basically I won’t be lumpy reading data the only are interested in the right function then for the client

See you packet all right you know I can I check the box it’s abstract give me some keystrokes extend EC packet and this one is going to be right sent from the client we don’t actually need to write any data we’re just going to read send from client right

PETA all reminders pretty much now let’s make our hello world packet so s packet hello world so simple server same naming scheme then best packet the unimplemented method and we’re actually not going write any data to this packet because on the client side of things if we look back you can see

We’re not actually reading any data we’re just printing out server says hello hard coded so no need to send any data and we can be lost or not you can read it I’ll be covering more extensive packets and sending and receiving different types of data in the next

Couple of tutorials but this is gonna be the simple packet you’re sending s packet hello world next thing we need let’s make another class called packet at ease now if you remember from my last video I told you to remember this number for me at 74 it might be different for

You we need to remember that we’re gonna write it down to here we’re gonna say public static final int that’s a packet hello world equals 74 now the reason we have to do this is the way I am registering my packets I have to tell minecraft the the server what packet ID

It should get the client and the server normally when registering in just the order you register things in but since I can’t edit the server jar well you okay for this tutorial I’m not going to edit the server jar I’m gonna write a plug-in that can work with any

1.8 jar but you yeah you theoretically could do it the other way but I never never mind forget the past things I said I should edit this out we just need to know the ID so when we tell the server hey this packet exists here’s the ID

Here’s the class and then it figures it out so I’m going to close all these I don’t need them open now let’s make hard class which is going to be custom mr. hanket manager this is gonna handle everything with registering custom packets and sending custom packets and all that jazz

I’m gonna try to go slow for this because this is gonna be a complicated piece of poetry so we’re gonna say private static final Hirshman a class of a wild card extends you see packet it’s not gonna looking import things for a little bit and then we’re gonna say

Packet type which is a protocol of classes they pack it too tight equals new I guess we could just copy this friend paren semicolon role shift o imports everything make this bigger now we want a public static void register free GI 3G is register packets but I do

It P ACK I say one word and then I type another one yeah alrighty so here comes kind of the main bulk of it we’re just going to the private static void register packet class a wild card extends EC packet packet class in packet Aidid senders an import sender from

Protocol it we’re going to say packet type in packet type good enough equals new packet type we are going to say protocol dot play because I’m sending all my packets over play you know then we want to say sander is that current ID is going to be a packet ID legacy ad you

Can set to negative one we want to then say packet to type packet to know this I could you type dot put the package class I guess they were going to say let’s see final I guess this could be finalized I don’t want that to change

When I say final inna row to call from tocall equals enum protocol plank now that I think about it I’m actually going to that here we’re gonna change this to protocol this is never gonna change oh man I’m dumb you know they’re both named play different things yeah I got

Mixed up I need to cut that out we need to say final protocol direction all Direction equal package rendering in line if statement packet type talk is client question mark you know protocol direction not server down calling me non-pro to call direction dot clean now let’s do a try-catch and accept its

Legal argument exception or illegal access exception uh operators so we’re going to say basically what we’re going to try to do is we need to we need to call up protocol a punch packet ID in the package that’s what we want to do but a protocol by a isn’t actually

Public so we need to do a little magic here I’ll call it in order to put it to the correct place in heat in protocol direction so it’s just like what we’re doing our client accept a lot more complicated in in the way of doing it so

We’re going to say map an enum protocol direction you know protocol direction come a by map of integer to class of a wild card that extends ext env a packet that the wild card is just a wild card limit equals cast of this of field definitely yield utils dot read field

And we want to read a field forget which one is that we want to do we want to I guess yeah we just want to say sorry read field um let’s see that would be protocol J as the object truth and I believe it is the

This one yeah this is a by map I import everything not all should be fine now that stupid long thing just to get the map now we’re going to say by map keep Singh by like dy by map integer and TE by map of integer comma class a wild card sends

Packets of a wild card by map get Oh what I could a map not get and we want to pass it in directions this is supposed to be integer then we want to say bye man put the integer of our packet ID and then the packet class and

Now this is going to error out and we’re just going to say cast it then we’re gonna save them at bot putts direction climate that it should be it for that bride now we’re going to say map of class of wild card you know protocol was appalled

Better name for it equals cast this excess sores don’t get filled access or you know protocol class map doc class through oops supposed to be that one there we go that’s spelt right then we’re gonna say map put package class who don’t that one now we just got

Another couple of things more – right I know so we want to say public static void send custom packet to the bucket player will do s packet we want to send import the bucket player you want to send to any type of that’s packet so I mean I guess all these technically

Actually well no yeah no yeah we need to register client packets too but for sending we just want to send into that so we’re going to say package container sorry I’m being a little bit confused it’s just because we don’t have a script in it really sure written one container

Equals new equal hello the equals new packet container packet type packet to type get packet hit class pama packet we’re going to say try and we were just going to catch innovation in I in OB I can’t with belt I and the location target exception then we’re just going

To print stack trace and while I’m at it actually to do check to make sure the plant is is an example client right before sending I will cover that in future tutorial but problem is if you send a packet that the client doesn’t know it’ll just be disconnected from the server and we

Don’t want necessarily you might not want people to be disconnected from the server if if they’re not using your client so yeah I mean want vanilla clients to be able to play as well but then if we want to we can kick vanilla clients and only allow our claim if we

So choose so yeah if we so choose to word waited my 40 networking okay so we’re going to do miss a protocol library that get protocol manager send server packet player is gonna be player that’s gonna be container should be good for this thing and then I’m also going

To work a public static packet tight get custom packet type give it a class wild car that extends easy packet plans We’re just gonna return packet packet to type now all that’s over just gonna cross our fingers and hope it works um few more things we got to do though big vocalist has done them we need to actually register our packets we’re willing to say register packet packet is

Going to be s packet hello world dot class packet ID is going to be in class packet I eased aspect hello world and of the sender is server server you’re sending packet that makes sense now in our main thing we are going to say we want to initialize all the packets we’re

Going to say some packet manager doc register packets and then what I’m gonna do is when the player joins the server we’re just going to send them a HelloWorld packet so I’m going to say at event handler player join or the player join event yeah it’s

Been a while since I’ve done some actual bucket stuff so you know what I want to also do is let’s do player P equals get player oh this temporarily for my testing server I’m going to say set game mode to be game mode creative and I’m going to P

Dot set off through can off myself as well every time I join because it’s an offline server you still need to do that now we’re gonna say a custom packet manager send custom packet player and new s packet hello world so I called it peanut player okay now let’s export our thing we’re

Gonna say export this finish yes three another thing we have to do though is we have to make our server offline mode for testing so I’m going to say what says online mode false I personally want to be peaceful mode and I guess I can be creative by default that’s about it you

Really need to do now let’s start our server and hope it doesn’t crash because that would be unfortunate what did I do wrong class caps accession default fields accessor cannot be cast a map okay well I’ll be back and I’ll just edit this all out well I

Found my bug I’ve heard to say it yet and passed protocol okay let’s try this again so we’re going to export it and then we’re going to say finish and let’s start server backup and hopefully should not error this time haha look at that we didn’t error perfecto

So now what we’re gonna do is click on our client package and run it I really didn’t help all this works because I’m not sure how much more time we’re going to have before my roommate comes on in and then it’s can’t really record because it’s just super loud in here and

Stuff alright let’s go to multiplayer we should see our server we say join and we don’t see our we don’t see it oh you know what might be the problem now that I’m thinking about it um what is it like it plugins manager what is it register

Maybe I’m just wrong no I want to say register their events this this rate that’s how bucket works I have to register my listener ok let’s export or plugin again you know this is why I should really write a script for things oh yeah see if this

Works and we should see in here ha ha ever says hello we go to a packet whoo-hoo-hoo okay it’s gonna be if this tutorial next one hopefully you’ll have a script or I might just record it right now with my roommate still out you know Okay yeah oh thanks for watching I’ll see you guys in the next video