Basics of Replication | Instances, RepNotify, RPC's | Multiplayer Tutorial Series | UE5

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In this video we take a look at the basics of replication. We will cover the concept of replication and what it takes to replicate the server instance to the client instances to keep everyone in sync.
We also take a look at how we set an actor to replicate, we look at Replicated and RepNotify variables, and we take a look at Remote Procedure calls, also known as RPC's. The events Run on Owning Client, Run on Server, and Multicast.
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Here is what we cover in this video:
00:00 - Intro
00:40 - What is replication?
01:47 - Applied replication example (Instances)
06:31 - Replication, Replicated Variables/RepNotify, RPC's
10:07 - Taking a look at Replicated and RepNotify variables
13:20 - Taking a look at RPC's
17:10 - Taking a look at a replicated actor example
21:20 - Outro
#UnrealEngine #Multiplayer #Sessions
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[@Kekdot]

Hey guys, 👨‍🏫 My Patreon link: www.patreon.com/kekdot Download Project Files | Premium Tutorials | Courses 💦 Get our Game on Steam | Kekdot Center: store.steampowered.com/app/1487180/Kekdot_Center/

[@OnionCutter64]

I usually don't comment but HOLY JESUS this is the easiest and most beginner-friendly explanation I've ever heard about replication. Thank you SO MUCH for providing this easy to understand guidance

[@SomeoneOnlyWeKnow.]

I'm a native English speaker but I love how you even explained what the word itself means to increase accessibility to those who may not know!

[@spectrecular9721]

I like how every time he said "The two balls on top of the guys head", he tried not to laugh

[@Kekdot]

Hehehe

[@RDD87z]

omg i recommend to watch this video to anyone who wanna understand what replication is and how multiplayer works. THIS IS SO WELL DONE AND EXPLAINED, thank you so much!

[@LJ_Dev]

Is nice to have clean videos like this on this topic. Thanks!!

[@RobinDale50]

For RepNotify when it changes, it should be noted that, in addition to that special function being called, the changed state is *automatically synced to the clients* as well. It sounds obvious, but its good to make that clear. So, for instance, if you only need that variable to be updated to all, and no code processing, you just change it on the server and it reflects to all, and you don't even need to put any code in the special function

[@francoisclement416]

I loved the presentation, makes learning so much faster!

[@PandaCubed]

Just came across your videos and wow, they are so useful. Love the explanations and examples. I have been wracking my brain on when to use the different replications and how all this multiplayer stuff works. Great video

[@HeartsintheWind]

You are the only person that got me to understand the RPC issue. Thanks man

[@Kodamaaaa]

This really helped me understand replication. Thank you!

[@3BEEZ]

Brilliant Tutorial 👏🏾

[@bibCorp]

Fantastic video. Very well explained!

[@HuwRees]

This is amazing, thank you. If everyone explained things as well as this, my game would be finished in a month!

[@pushthetempo3125]

Thank you for this tutorial, helped a lot

[@elmonsieur9905]

you are a beast , i understood every single seconds in this video, its because of your way of speaking its super good, this is by far the first video i saw after 30000 that i understood the repnotify finally, thank you so much

[@elmonsieur9905]

but then i have one question, you said the switch authority will run only on server, why we use it then if we can simply just apply the replication so we send it to all clients, why we are using the switch authority please

[@Kekdot]

Hey Monsieur, The switch has authority node has two pins: ‘Remote’ and ‘Authority’. Since some events are run on both the client and the server, for example a Multicast or a RepNotify, a Switch has Authority can be very useful. For example: Let’s say you have a RepNotify that spawns a particle. But then in that same RepNotify you want the server, and server only, to also do some additional logic, maybe add some score when the RepNotify fires. Then in that scenario you can use a Switch has Authority to run certain code only on the ‘Authority’ and not on the ‘Remote’ aka client, within that same RepNotify. ‘Authority’ = Server ‘Remote’ = Client

[@elmonsieur9905]

@@Kekdot ohhh i got it now!! thank you a lot for taking your time to explain to me, appreciate it a lot 💖

[@Dieselbird]

Great video it really helped clear some things up for me on replication!

[@BAMBAMBAMBAMBAM-]

This is such a cool way to do a tutorial. Thank you for posting! Just a tip for future videos, white text does not work well on light-blue backgrounds

[@danielgbat89]

Best explanation I've ever seen.

[@moejahi3d3]

There are many Replication tuts on the net..but none the Kekdot way haha. This was such a wholesome and awesome vid. Really loved the presentation! got my sub at least!

[@unrealdevop]

Great video, very well done.

[@arjanb7158]

Great content! Bedankt!

[@meijinjake3611]

you earned my sub

[@abraarbala]

Great Stuff!

[@rifat.ahammed]

Thank you soo much

[@PraxisOff]

OMFG thank you soooooo much. It's really clear. You take the time to explain everything. All the other videos I've seen is examples and tutorial but they don't explain how the tools works (well yes) but in their context.

[@ComfortZoneComic]

im new but this : != KEK .... this==POG.....subd

[@psyco4452]

quick question, did you made an exemple of a displayer of infos, i mean by that, im using advanced session plugin for UE5, i got thoses extra features link to my instance when creating the session then it's inject into it the info i want ( aka is privatematch, should advertise, ect,ect) . now the infos are stored into the game session, problem im having is neither the infos neither the steam player infos show up on clients ( i can't make the basics infos like currents players and stuff ( using your onlog/logout shematic) ) do you plan to do a complex lovvy server displayer later on ? been 4 weeks i try to fix that hell. but i got werid stuff happening, like my player displayer doesn't works only the las onpost login event... all they others clients see the update occur.

[@phantomabid]

BALLZ !

[@taigabit]

I have a question regarding dedicated server and game project. I can change the functions and what not to be "run on the server" to process specific logic on the server. But.. how does it work with a dedicated server. Is it a copy of the game project package running on another machine that is running? Do I have to view it as two unreal projects that I have to manage separately? Like a viewer/client side and the server side? Would it mean I have to "split" my game logic at the end of it all for a dedicated server before packaging to define what code and blueprint belongs to the server and what to the client? I cant get this into my head and would greatly appreciate a nudge into the right direction of thought.

[@ruellerz]

Loce this video style

[@bobslop9136]

This is some next level explanation! Outstanding!😍

[@stormolflak]

Nice

[@Nanu_art]

Please help Please help I made a pickup system in which client and server can pick up the object easily but problem comes here that when server picked up object,client can see this in his window that server has a object but when client pick up object server can't see this and from server's view the object placed on ground only...but when server press E (input action for pickup) then client get object in his hand and now server can see client has object ( if client already has object but not show in server screen but when server press E client get object which he has already in his hand before What I do ?

[@plasid2]

I hear deafult character movement is useless in multiplayer becouse is problem jitter and synchronization, that why better idea is use GMC pluging but is very expensive it is true?

[@PapaBearFreddy]

You should do a udemy or a course for step by step to build a multiplayer RPG game

[@BlizzardZGaming]

Could you show how to replicate the rotation movement component for a spinning platform, I've followed the steps but the client side jitters

[@Kekdot]

Hey Blizzard, Yeah in my next video’s i’m going more in depth and I’ll show examples like the one you’re asking. And to be clear, I have not yet covered the steps that you’d need to undertake to fix your issue in this video, hence your setup is still incomplete and jittering. This video is the pure basics of replication, in order to achieve fully stable/reliable replication there is a lot more that has to be combined then what is shown in this basic video.

[@YndarX]

@@Kekdot Any updates on when the "next" video's are going to be coming with more information on these topics? Been 9 months since this comment was made and don't get me wrong I love the videos and how well they are explained. Just looking to further my understanding of these topics. Much appreciated!

[@baker_dev]

do u know are u great man

[@Kekdot]

Ah it's 1080p now!

[@nicksparrow009]

Why not use Replicate Movement?

[@SuperVillianStudios]

Hey, So how would you replicate from client to server?

[@Kekdot]

Client fires of a 'Run On Server' Event, then the Server can choose how it replicates it back to the clients. A commonly used way to replicate back to the clients is to then Multicast or set a RepNotify.

[@SuperVillianStudios]

@@Kekdot Ahhh, I see. Many Thanks

[@cyqry]

@@Kekdot This. In the case of a networked game only the server should have authority. Dedicated servers would not have an attached client, and I believe a listen-server (which would have a client) would execute all the "run on server" anyways. A client should never be directly messaging *other* clients.

[@Kekdot]

A client can’t directly message another client. Not sure what you mean. Only client-server communication exists. Client to client communication does not exist.

[@cyqry]

@@Kekdot Sorry I misread what SuperVillain meant, thought they were asking about having a client send the message directly.

[@hiramhill1305]

Can you seamlessly switch between multiplayer and single-player? Can you make a world initially single-player but decide to make it multiplayer or invite guests later? Can listen server based multiplayer games work offline and function like single-player? Would a multiplayer game acting like single-player, still work with sessions? Would you need to save the world before ending a session so that you can have multiple single-player worlds?

[@jacobfoster]

From my understanding, any multiplayer logic will additionally work in a standalone offline version of the game. This is why Unreal Docs recommend implementing replication from the start of a single-player project just incase you do decide to make it multiplayer later on - because it will work for single-player too. I believe this is because in an offline standalone game, Unreal treats the computer as if it is the server.

[@Kekdot]

True, and in an online game, Unreal also treats the computer (host, session creator) as the server.

[@eclecticgamer5144]

This top is *incredibly* difficult to find any information on... Thanks.

[@pwnermies1]

I don't mean to be an a-hole, but basically all of this information is in the unreal docs. It's just not as easily understandable.

[@eclecticgamer5144]

@@pwnermies1 Yep, still an A-Hole. So, let me clarify. It's *incredibly* difficult to find any *USEFUL* information on... I've read the docs. It never worked right. I've watched tutorials before. Followed step by stem. *never* worked even slightly. This is the first one that gave me *any* progress. Once I made some progress I could figure out the rest on my own. It's not that I didn't understand the docs. It flat out didn't work. Ever. I didn't spend a whole lot of time, as multiplayer has always been of minimal importance in my earlier projects, but I've tried many times over the years to zero progress. On top of all that, you're belittling the contribution of the authors video. So, ya, you should probably just delete your sh**y comment.

[@ruellerz]

Ugh i gotta review how to replicate movement. I did multicast and its super laggy. Not reliable set

[@God0fTime]

use the built in stuff within the character movement component don't multicast it yourself... their framework with prediction is AAA

[@Kekdot]

I think he’s talking about switching speed in runtime, like sprinting in multiplayer. Well if that’s the case @ruellerz: Simply change the movement on both the owning client, and on the server. If you’re the client simply locally change the speed, then call an rpc that changes your speed on the server. Now client and server are perfectly in sync and no multicast is required. Your lagginess is caused by not directly setting the speed on the local client first causing the client to be fully depedant on the server update, thus resulting in laggy movement. If you’re the server however, simply only change your speed locally. (As you already have full authority and only exist locally anyways, rest sees you as a proxy so is smooth by default)

[@jojoblaze]

Nice video, but why do you move pawn and camera all the time? It's a bit annoying. :(

[@michaelsparkson]

Looks like 1080p.

[@Kekdot]

It's 1080p now haha, but it will be 4k in probably 1 hour!

[@pippa0154]

@@Kekdot IT TAKES THAT LONG TO UPLOAD A 4K VIDEO?

[@Kekdot]

@@pippa0154 ITS 4k NOW! but yeah that stuff takes like 1 day lel