WEBVTT

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Hello, this is Youngho Lee

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In this unit, we'll learn take pistol and release pistol actions

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Unlike single play

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we'll use actor replication

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when character takes or releases pistol

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on network, and how to sync the data between players

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The first thing we'll study is taking pistol

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To do this

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you'll use owner setting, server RPC and NetMulticast RPC

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And to sync the take pistol animation

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we'll learn how to use property replication

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Secondly, we'll learn release pistol

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Similarly, we'll use RPC

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and separate the logic that the server will process and

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the one that the client will

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Take pistol

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First is take pistol

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Let's see

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We'll first learn Standalone

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that is, single player, and then multiplayer

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We'll divide it into these two situations

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The one on the left is Standalone

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single player

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On Standalone, you'll get an input

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for take pistol

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then you'll set the owner

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and will actually take the pistol

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With the take pistol input

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owner setting takes place

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and lastly attaching

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so that the pistol is attached to me

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This is what we'll do on Standalone

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single game situations

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But in network

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when there are server and client coexisting, take pistol can

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have errors if it uses this flow

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What might happen is the client took a pistol

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but other clients

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or the server might not be able to know

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that this client took a pistol

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This is Standalone

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Then let's expand this

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to multiplayer

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network mode where many players can join

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It's the diagram on the right

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Client, similar

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to Standalone, gets input

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They get input first

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and then with this input, they'll request

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the server using server RPC to take a pistol

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Different right?

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On Standalone,

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they just set owner and took the pistol themselves

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but here, the client isn't taking the pistol themself

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but requesting the server to do that

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Then the server will receive the request from the client

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and do owner setting

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and after that's done

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tell's them that they can take the pistol

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so they will attach

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the pistol to the hands of

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the client which is done

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by the client

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Why? Because that's a visual aspect

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This part, the server can't do

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and the client must

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So the server's role is

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to get the input from the client

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and to test range

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and set owner

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Owner setting must be done in the server

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I've been telling you this

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but if owner setting is done by clients

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the server or other client can't know about that

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so communication is impossible

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Owner setting must be done by the server

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so that the owner's

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net connection object can communicate

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The server receives request and sets owner

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then to all clients

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it will send take pistol request saying 'this person's going to take a pistol'

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Then all clients will

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get this message

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and do the logic that makes that client take a pistol

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The overall flow is like this

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Then let's make this using codes and

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Unreal Engine editor

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First let's go to Visual Studio

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On Visual Studio

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until now, we used this NetActor for RPC

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and property replication

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but now we'll

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learn about NetTPSCharacter multiplayer

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So first, on Visual Studio

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let's go to NetTPSCharacter

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We'll go to the header file

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Go to NetTPSCharacter header file

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and on the very bottom

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It says network related member here

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Here, to separate

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I'll add public

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We're going to add the part that sends the take pistol message with a server RPC

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UFUNCTION, and we needed to put server option for server RPC

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Then take pistol must be performed

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So we'll put reliable

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void, ServerRPC, TakePistol

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You can put an underscore between the serverRPC

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and TakePistol or not, it doesn't really matter

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You can do as you want

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For the function name, we just need to say that

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it's a server RPC function

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Then when we build

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on the generated header file

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server RPC function implementation is added

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And what we actually need to implement

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is not the ServerRPC TakePistol

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but ServerRPCTakePistol_Implementation

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This is the one

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So on NetTPSCharacter.cpp, ServerRPC TakePistol_Implementation

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We need to put the function name like this

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Then internally, ServerRPC TakePistol function is implemented

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and in that function, this implementation

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will be called

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Like this, implementation is added

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Then, with this ServerRPC TakePistol part

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we need to move the take pistol parts

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I'll move this function's placement first so that it can be close to

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TakePistol function

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I'll move it next to the TakePistol function

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I'll put it under it here

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so that it's easier to see

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Here, this part down here

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If we have a pistol or not

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can be checked here

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This doesn't need to be given to the server

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That could waste packets

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So under here, if one has a pistol

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we return and not perform anything

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and when one doesn't

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this part down here is subject to checking

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So it will be the part of taking a pistol

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This part all moves to where?

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To ServerRPC TakePistol

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I'll cut this part

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from TakePistol

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and paste it here on ServerRPC TakePistol

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Then it will be moved to

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ServerRPC TakePistol Implementation

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Then on TakePistol

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This is a function that is called when input is received

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It requests to the server when that happens

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Like I explained with the diagram

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now we're on request to server

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so it has to request to the server saying

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'I'm going to take a pistol'

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This is ServerRPC TakePistol

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So the request code here

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will be ServerRPCTakePistol

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If we directly call using Implementation

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This isn't from client to server

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but when it is the server, calling itself

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it being the server itself

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Server can call with its own function

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But when this is a client

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when processing an input from a client

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it isn't the server itself so it can't call this function

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If it's called

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internally

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if server RPC interally works

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calling this function

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then this function will be

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internally called

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so if we call it here directly

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from the client

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this can cause a problem, why?

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Because this isn't the server

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This is a client, so it can't call a server's function

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It has to be using an RPC function to call

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and this function being called inside the RPC

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Now, the client has sent

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a request to the server

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We're here

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Client requesting the server

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This part just took place

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Then the server must do the logic of

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setting the owner and

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sending message to all clients

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Then take pistol

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the attach part

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must be done in the client

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The server only requests to attach

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Right?

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Great

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Then let's first build

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and see how it turns out

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We can easily guess what that would be

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Input comes in

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Then it requests to the server

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It'll say 'I want to take a pistol'

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Then the server will call this function internally

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and the take pistol will take place

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Then let's think about the case where there are two clients

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Let's say one's here

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and another one's here

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Then

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This client is

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in the server

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We'll call this one C1

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and this one C2

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This one is in the server

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Here, let's say that C2

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requests ServerRPCPistol

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Right, then this screen

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where these two are in, no matter the server or client

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will show both of them

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When in this situation

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ServerRPC is requested

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For C1, taking pistol code

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will be performed

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So it will take a pistol

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But for C2

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this thing is perfromed in the server

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but it hasn't sent the request

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to other clients yet

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so this guy, even though

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this C2 is going to take the pistol can it take it or no?

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It can't

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The re-request hasn't come yet

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The server will already have

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performed the things down here

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so it will take the pistol

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But the client, even though

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it requested to the server

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hasn't received the request from the server

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telling it to take a pistol

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so it can't take the pistol

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So when we run it

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the character in the server will take a pistol

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but will client's screen show it taking the pistol?

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It won't

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Let's check that

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Let's run two of these

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Great

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First, look at the server screen

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To perform both of them

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I'll check on New Editor Window

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Not Selected Viewport

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Let's do New Editor Window

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Then, on the window

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it says server

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This is the server window

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and let me open a client window

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next to it

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Let me do that

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The one on the left is the server

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and the right is the client

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Let me take the pistol from the server screen

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Then to the client, it should show the server character taking the pistol

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but as I told you

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client doesn't receive any RPC

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so the server character taking a pistol

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will show on the client's screen or no?

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It won't

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On the other hand on the server's screen

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you can see it

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Right

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But the client

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can't see anything

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The server shows taking the pistol

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but on the client window on the right

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it doesn't show the server character taking anything

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Why? On the server

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the take pistol logic was performed

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but a request to the client to take a pistol

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was not sent

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so this problem occurs

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So now let's solve that

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For that, for every character to take pistols

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we'll use a

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NetMulticast RPC

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Go to NetTPSCharacter's header file

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and under server RPC

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we'll put NetMulticastRPC

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This time, instead of server, we'll have NetMulticast

285
00:15:12.520 --> 00:15:15.960
and then void Multicast

286
00:15:15.960 --> 00:15:20.960
Then MulticastRPC_TakePistol

287
00:15:20.960 --> 00:15:27.039
And here, const a actor pistol actor

288
00:15:27.039 --> 00:15:29.119
I'll put that here

289
00:15:31.039 --> 00:15:34.479
Why? This part needs to tell the clients

290
00:15:34.479 --> 00:15:36.159
what pistol to take

291
00:15:36.159 --> 00:15:38.800
so we're going to have a parameter here

292
00:15:40.960 --> 00:15:46.200
We'll add implementation under the server RPC

293
00:15:46.200 --> 00:15:52.919
Under server RPC, NetMulticastRPC TakePistol is implemented

294
00:15:52.919 --> 00:15:57.159
There's also _implementation as well

295
00:15:57.159 --> 00:15:58.000
for the same reason

296
00:15:59.960 --> 00:16:01.840
Great

297
00:16:01.840 --> 00:16:06.960
Then the server RPC calls this MulticastRPC

298
00:16:06.960 --> 00:16:08.810
and MulticastRPC

299
00:16:08.810 --> 00:16:12.400
needs taking pistol part

300
00:16:12.400 --> 00:16:13.900
As you see in the screen

301
00:16:15.000 --> 00:16:18.080
the taking pistol part

302
00:16:18.080 --> 00:16:21.400
isn't here but in the server

303
00:16:21.400 --> 00:16:23.700
So like in this diagram

304
00:16:24.840 --> 00:16:27.520
after the owner setting part

305
00:16:27.520 --> 00:16:28.919
and the taking pistol part

306
00:16:28.919 --> 00:16:31.880
actually attaching the pistol to the actor

307
00:16:31.880 --> 00:16:36.000
and such must be done by the clients with Multicast

308
00:16:36.000 --> 00:16:37.580
We'll move those here

309
00:16:40.280 --> 00:16:45.200
So on MulticastRPC, we'll add

310
00:16:47.680 --> 00:16:48.799
attach pistol, this part

311
00:16:48.799 --> 00:16:52.080
We need this part not here, but under here

312
00:16:52.080 --> 00:16:53.139
We'll do that

313
00:16:54.639 --> 00:16:55.600
Attach pistol

314
00:16:57.140 --> 00:16:59.520
Above here, owner setting

315
00:16:59.520 --> 00:17:03.180
and data setting will be done where?

316
00:17:03.180 --> 00:17:05.280
On the server

317
00:17:06.880 --> 00:17:13.280
Under here, MulticastRPC TakePistol

318
00:17:13.280 --> 00:17:17.479
and we'll put what's to be attached

319
00:17:17.479 --> 00:17:20.880
That will be Pistol actor

320
00:17:20.880 --> 00:17:22.960
Put the pistol to be attached

321
00:17:22.960 --> 00:17:25.780
and the message will be sent to clients

322
00:17:27.840 --> 00:17:29.440
It looks like simply calling a function

323
00:17:29.440 --> 00:17:31.719
but communication happens internally

324
00:17:31.719 --> 00:17:36.079
So the server sends to clients

325
00:17:36.079 --> 00:17:38.920
MulticastRPC with the message telling

326
00:17:38.920 --> 00:17:42.199
to take pistol, TakePistol is internally sent

327
00:17:42.199 --> 00:17:45.440
Then the function is called in the client

328
00:17:47.920 --> 00:17:51.399
Let's build

329
00:17:52.119 --> 00:17:54.160
This is an RPC function

330
00:17:54.160 --> 00:17:56.680
so it's the server and a client

331
00:17:56.680 --> 00:17:57.880
It's both

332
00:17:57.880 --> 00:18:02.319
I did all this in the server and did Multicast

333
00:18:02.319 --> 00:18:05.719
It's the server and a client at the same time

334
00:18:05.719 --> 00:18:08.800
but they are logically separate

335
00:18:08.800 --> 00:18:11.439
Physically the server and client is together

336
00:18:11.439 --> 00:18:16.880
but logically, C1 and C2 are separate

337
00:18:16.880 --> 00:18:20.239
So now, C2 has RPC requested

338
00:18:20.239 --> 00:18:23.599
to the server saying 'I want to take a pistol'

339
00:18:23.599 --> 00:18:25.599
Then the server

340
00:18:25.599 --> 00:18:27.959
does all this

341
00:18:27.959 --> 00:18:29.280
and sends a Multicast

342
00:18:29.280 --> 00:18:31.959
How? It sends this

343
00:18:31.959 --> 00:18:34.199
to all clients

344
00:18:34.199 --> 00:18:37.119
Although this is physically here together

345
00:18:37.119 --> 00:18:41.160
but this is ultimately like this logically

346
00:18:41.160 --> 00:18:43.400
So from server to client

347
00:18:43.400 --> 00:18:45.799
message is sent with Multicast

348
00:18:46.402 --> 00:18:47.402
Got it?

349
00:18:49.599 --> 00:18:53.340
Then the client will perform take pistol

350
00:18:55.400 --> 00:18:57.699
Let's build

351
00:19:04.319 --> 00:19:06.800
And we'll run

352
00:19:06.800 --> 00:19:09.239
but let's think about what problem might happen

353
00:19:09.239 --> 00:19:10.519
when we run it

354
00:19:13.102 --> 00:19:14.102
Play

355
00:19:15.199 --> 00:19:18.459
Server open, and client as well

356
00:19:21.959 --> 00:19:25.400
I'll take the pistol from the server screen

357
00:19:25.400 --> 00:19:28.260
Then what will happen

358
00:19:29.520 --> 00:19:31.320
It suddenly stops

359
00:19:32.640 --> 00:19:34.759
and the editor shuts off

360
00:19:36.099 --> 00:19:39.119
Why? Analyzing the error message

361
00:19:42.839 --> 00:19:45.880
Here, it says NetTPS Crash Repoter

362
00:19:45.880 --> 00:19:47.520
Don't skip this

363
00:19:47.520 --> 00:19:50.199
It shows what errors happened

364
00:19:50.199 --> 00:19:54.040
Here, it says exception error

365
00:19:54.040 --> 00:19:57.419
Access violation, reading access, and then null

366
00:19:58.839 --> 00:20:01.560
A null subject

367
00:20:02.622 --> 00:20:04.961
There's no value in the pointer

368
00:20:04.961 --> 00:20:08.041
I entered that place so an error occured

369
00:20:08.062 --> 00:20:11.122
Look

370
00:20:11.122 --> 00:20:13.262
There was an error in show crosshair of mainUI

371
00:20:13.263 --> 00:20:16.642
and on the ninth line of mainUI cpp

372
00:20:16.642 --> 00:20:19.161
this occured

373
00:20:19.161 --> 00:20:23.981
Let's go to ninth of mainUI

374
00:20:25.562 --> 00:20:30.142
Go to ninth line of mainUI cpp

375
00:20:30.143 --> 00:20:33.902
Let's see what it is

376
00:20:33.902 --> 00:20:36.721
show cross needs to show this but

377
00:20:36.722 --> 00:20:39.661
there are no image crosshair

378
00:20:39.661 --> 00:20:43.881
Then we'll need to move to where it called these show crosshair

379
00:20:44.861 --> 00:20:47.760
That being nonexistent

380
00:20:51.420 --> 00:20:55.241
There was no problem here

381
00:20:55.241 --> 00:20:57.902
Where it called this

382
00:20:57.902 --> 00:21:00.762
That's AttachPistol

383
00:21:01.842 --> 00:21:06.662
It's this part

384
00:21:06.662 --> 00:21:11.601
It was going to receive Multicast, attach pistol and when doing that

385
00:21:11.602 --> 00:21:14.221
attach all these onto component

386
00:21:14.221 --> 00:21:19.561
and do this on the mainUI and show crosshair

387
00:21:19.562 --> 00:21:22.401
But looking here, mainUI

388
00:21:22.401 --> 00:21:25.721
is null so this part caused the error

389
00:21:25.742 --> 00:21:27.742
I'll put a breakpoint here

390
00:21:28.881 --> 00:21:31.820
Then we'll perform it on debug mode

391
00:21:40.240 --> 00:21:42.090
When working with Unreal

392
00:21:42.090 --> 00:21:45.520
performing debug mode on Visual Studio

393
00:21:45.521 --> 00:21:47.881
is pretty useful on finding runtime errors

394
00:21:47.881 --> 00:21:50.281
I'll play it again

395
00:21:50.282 --> 00:21:52.541
and also a client window

396
00:21:52.561 --> 00:21:57.841
I'll go forward and take with F, it says this

397
00:22:00.922 --> 00:22:03.761
Here, the error happened

398
00:22:03.781 --> 00:22:08.400
here on the Net Nulticast TakePistol

399
00:22:08.400 --> 00:22:11.321
On Net Nulticast TakePistol

400
00:22:13.842 --> 00:22:14.842
Right here

401
00:22:16.002 --> 00:22:18.662
This part was where the error happened

402
00:22:18.662 --> 00:22:22.462
So the mainUI

403
00:22:22.462 --> 00:22:23.462
there's no memory here

404
00:22:23.462 --> 00:22:26.642
which means it's null here

405
00:22:26.642 --> 00:22:29.001
so we need a code here

406
00:22:29.002 --> 00:22:31.152
Then why does this problem happen?

407
00:22:31.152 --> 00:22:33.881
Why is there nothing in here?

408
00:22:33.881 --> 00:22:36.100
That's because of these

409
00:22:37.921 --> 00:22:41.700
Let me use this picture to explain

410
00:22:45.040 --> 00:22:46.680
So here

411
00:22:49.180 --> 00:22:53.502
PC means player controller

412
00:22:53.502 --> 00:22:56.681
and this one also means player controller

413
00:22:56.681 --> 00:23:03.801
NetMulticast will be sent

414
00:23:03.801 --> 00:23:06.442
It will call

415
00:23:06.442 --> 00:23:12.022
I said that NetMulticast is Actor Replication

416
00:23:14.202 --> 00:23:17.682
This literally means actor

417
00:23:17.682 --> 00:23:22.361
It means that when the same object is in a world they can communicate

418
00:23:22.362 --> 00:23:23.781
with each other

419
00:23:23.781 --> 00:23:25.501
It means communicating using actor

420
00:23:25.502 --> 00:23:27.541
Actor replication

421
00:23:27.541 --> 00:23:33.401
Then looking at the mainUI

422
00:23:33.401 --> 00:23:38.040
what were the conditions of this being made

423
00:23:38.040 --> 00:23:39.721
Let's take a look at the code

424
00:23:42.120 --> 00:23:46.640
It says InitUIWidget

425
00:23:49.082 --> 00:23:51.262
From here

426
00:23:51.262 --> 00:23:54.302
Do not process if player is not controlling

427
00:23:54.302 --> 00:23:58.482
So if there's no player mainUI is not made

428
00:23:58.482 --> 00:24:02.581
Right? Do not process if player is not controlling

429
00:24:04.002 --> 00:24:05.602
Going back to the screen

430
00:24:06.942 --> 00:24:09.822
We sent a NetMulticast

431
00:24:09.822 --> 00:24:14.122
But the mainUI must have a player controller on that phone

432
00:24:14.122 --> 00:24:18.241
Only then the code logic runs

433
00:24:18.241 --> 00:24:22.360
We're saying that there are these two clients

434
00:24:22.360 --> 00:24:24.962
Both will show on the screen

435
00:24:24.962 --> 00:24:26.662
The top is

436
00:24:28.322 --> 00:24:30.702
what will show on the client's screen

437
00:24:30.703 --> 00:24:33.002
and the second like this

438
00:24:33.003 --> 00:24:35.962
The one below is the server

439
00:24:35.962 --> 00:24:38.281
From the server point of view, how would it look

440
00:24:38.282 --> 00:24:42.921
From the server, since the server has all player control

441
00:24:42.921 --> 00:24:46.082
Right? It has all player control

442
00:24:46.082 --> 00:24:48.662
so this problem will not happen there

443
00:24:49.502 --> 00:24:51.362
But from the client point of view

444
00:24:52.702 --> 00:24:55.662
Do I have player controller?

445
00:24:55.662 --> 00:24:58.281
I have mine but what about the other one's?

446
00:24:58.282 --> 00:25:01.821
No, it only has it's own player control

447
00:25:01.822 --> 00:25:03.241
So the other one

448
00:25:03.242 --> 00:25:05.061
Here, this SimulatedProxy

449
00:25:05.061 --> 00:25:07.840
character, the other one

450
00:25:07.841 --> 00:25:09.860
Not mine

451
00:25:09.860 --> 00:25:12.742
Does this one have player controller?

452
00:25:12.742 --> 00:25:14.882
On the client window, no

453
00:25:16.242 --> 00:25:17.822
Do you get it?

454
00:25:17.823 --> 00:25:20.261
I have player control over my character

455
00:25:20.261 --> 00:25:23.240
but for the other one

456
00:25:23.241 --> 00:25:26.300
is there player controller on the client's window? No

457
00:25:26.301 --> 00:25:28.760
Only the server has all player control

458
00:25:28.760 --> 00:25:31.960
the client only has its own player controller

459
00:25:31.961 --> 00:25:36.040
Then for this character which is a SimulatedProxy

460
00:25:36.040 --> 00:25:38.522
can there be a mainUI?

461
00:25:38.522 --> 00:25:41.162
No because there is no player controller

462
00:25:41.162 --> 00:25:44.381
but from our code logic

463
00:25:45.342 --> 00:25:48.582
when doing MulticastRPC

464
00:25:48.583 --> 00:25:50.281
It says attach pistol

465
00:25:50.281 --> 00:25:53.622
Up to here, it doesn't matter

466
00:25:53.622 --> 00:25:57.642
but here, it wants to call mainUI but

467
00:25:57.642 --> 00:26:00.681
mainUI is only made when there is player controller

468
00:26:01.422 --> 00:26:03.542
Right, but the counterpart

469
00:26:04.221 --> 00:26:07.120
Can there be a mainUI or no?

470
00:26:07.451 --> 00:26:08.451
No

471
00:26:09.031 --> 00:26:12.151
Why? Because there's no player controller

472
00:26:12.151 --> 00:26:17.022
So this attach pistol part

473
00:26:17.022 --> 00:26:19.882
can have a mainUI only when?

474
00:26:21.321 --> 00:26:25.282
When I'm controlling

475
00:26:25.282 --> 00:26:28.422
that is, when there is a player controller

476
00:26:28.702 --> 00:26:34.022
When there is player controller

477
00:26:34.022 --> 00:26:37.161
Because only then, mainUI can be made

478
00:26:37.161 --> 00:26:38.781
Using network terms

479
00:26:40.601 --> 00:26:41.601
autonomous

480
00:26:43.960 --> 00:26:47.980
Only when it is autonomous proxy

481
00:26:50.522 --> 00:26:51.362
it is possible

482
00:26:52.722 --> 00:26:54.122
Do you get it?

483
00:26:54.122 --> 00:27:00.400
So we need to test calling this mainUI

484
00:27:00.400 --> 00:27:01.300
What that is is

485
00:27:01.300 --> 00:27:06.441
if autonomous proxy, when I'm controlling

486
00:27:06.441 --> 00:27:10.160
This ultimately means is locally controlled

487
00:27:10.161 --> 00:27:13.211
Internally, when i'm the one locally controlling

488
00:27:13.211 --> 00:27:14.120
That's what if is for

489
00:27:14.120 --> 00:27:18.021
And when there is mainUI

490
00:27:18.021 --> 00:27:23.160
we'll call this

491
00:27:26.281 --> 00:27:30.041
Let's build

492
00:27:33.020 --> 00:27:35.480
and play

493
00:27:37.960 --> 00:27:40.660
Server window

494
00:27:40.661 --> 00:27:42.860
and a client window

495
00:27:42.860 --> 00:27:43.860
Let's see how it goes

496
00:27:43.860 --> 00:27:45.921
From the server, it takes a pistol

497
00:27:45.922 --> 00:27:49.881
On the client, it doesn't

498
00:27:49.882 --> 00:27:52.521
but let's see here

499
00:27:52.522 --> 00:27:54.701
Going closer

500
00:27:54.701 --> 00:27:58.240
on the client window

501
00:27:58.240 --> 00:28:02.960
you can see that the server character has the pistol in its hand

502
00:28:02.961 --> 00:28:06.760
Here, the server animation shows the animation too

503
00:28:06.760 --> 00:28:09.662
but the client just shows

504
00:28:09.662 --> 00:28:13.542
the pistol attached and the animation isn't synced

505
00:28:13.542 --> 00:28:18.080
So attach pistol is working properly

506
00:28:18.080 --> 00:28:22.562
but the animation isn't being synced

507
00:28:22.562 --> 00:28:25.202
Let's solve that

508
00:28:29.320 --> 00:28:35.180
Let's see how we sync animation

509
00:28:36.280 --> 00:28:40.640
On netpscharacter.cpp, bHasPistol

510
00:28:40.641 --> 00:28:43.680
it changes the pistol posession

511
00:28:43.681 --> 00:28:48.080
and puts this value to sync animation

512
00:28:48.081 --> 00:28:50.020
But look here

513
00:28:50.020 --> 00:28:54.081
ServerRPC function must be performed only where?

514
00:28:54.082 --> 00:28:55.582
Only in the server

515
00:28:56.022 --> 00:28:59.522
It's a code that's only performed in the server

516
00:29:00.361 --> 00:29:03.680
So it was true in server

517
00:29:03.681 --> 00:29:08.060
There's no way for the client to receive that this value is true

518
00:29:08.061 --> 00:29:12.400
So this value needs to by synced

519
00:29:12.400 --> 00:29:16.081
using property replication

520
00:29:16.601 --> 00:29:21.280
Let's go to bHasPistol implementation

521
00:29:21.281 --> 00:29:25.020
On netpscharacter.h bHasPistol is declared

522
00:29:25.020 --> 00:29:28.370
We'll add this option so that this part is

523
00:29:28.370 --> 00:29:30.201
synced on network

524
00:29:30.201 --> 00:29:34.181
u property, replicated

525
00:29:37.102 --> 00:29:39.452
We did this when we were doing property replication

526
00:29:39.452 --> 00:29:42.202
Then you'll know that

527
00:29:42.202 --> 00:29:45.120
to do this, the cpp file needs

528
00:29:45.121 --> 00:29:49.240
a function that starts with get lifetime

529
00:29:49.240 --> 00:29:55.360
void ANetTPSCharacter is already implemented

530
00:29:55.360 --> 00:30:02.961
GetLifetimeReplicatedProps function

531
00:30:02.962 --> 00:30:06.541
This function needs to be definedd

532
00:30:06.541 --> 00:30:11.720
Super, GetLifetimeReplicatedProps

533
00:30:11.720 --> 00:30:16.222
Call this and you need to do what?

534
00:30:16.222 --> 00:30:18.700
Register. Do

535
00:30:20.360 --> 00:30:22.340
REPLIFETIME

536
00:30:23.422 --> 00:30:27.623
and show the source. What from ANetTPSCharacter?

537
00:30:27.623 --> 00:30:32.080
Sync bHasPistol

538
00:30:34.040 --> 00:30:39.043
And this one has a red line, so on the very top

539
00:30:39.043 --> 00:30:41.083
we need to add include

540
00:30:42.401 --> 00:30:48.581
We have to put include the unreal network.h under net folder

541
00:30:50.401 --> 00:30:53.820
Let's build

542
00:30:56.240 --> 00:30:59.201
and see

543
00:31:01.763 --> 00:31:05.183
Just now, it was attached but the animation didn't show

544
00:31:05.183 --> 00:31:09.023
but now, both on the server and the client

545
00:31:09.023 --> 00:31:11.323
Look at the server screen

546
00:31:17.143 --> 00:31:20.383
The animation is showing

547
00:31:20.383 --> 00:31:21.903
and on the client screen as well

548
00:31:21.903 --> 00:31:24.063
the animation is playing properly

549
00:31:26.423 --> 00:31:28.883
Great

550
00:31:28.883 --> 00:31:30.863
Moving with the pistol

551
00:31:30.863 --> 00:31:35.461
the animation all works properly

552
00:31:38.660 --> 00:31:41.406
This was on take pistol

553
00:31:41.886 --> 00:31:44.520
Release pistol

554
00:31:47.263 --> 00:31:48.843
Next is release pistol

555
00:31:49.600 --> 00:31:52.950
For release pistol, similar to take pistol

556
00:31:52.950 --> 00:31:55.123
we will use RPC to

557
00:31:55.123 --> 00:31:58.183
sync on network

558
00:32:00.023 --> 00:32:03.363
As I mentioned, take pistol

559
00:32:03.363 --> 00:32:06.040
follows this flow

560
00:32:06.041 --> 00:32:08.100
On release pistol as well

561
00:32:08.100 --> 00:32:09.750
instead of TakePistol input

562
00:32:09.750 --> 00:32:12.600
a ReleasePistol input will come in

563
00:32:12.600 --> 00:32:17.361
and with the input it will request to server with server RPC

564
00:32:17.362 --> 00:32:22.081
Then the server will work on the owner setting

565
00:32:22.082 --> 00:32:24.261
and tell the client to put the pistol down

566
00:32:24.261 --> 00:32:27.241
by sending another request

567
00:32:31.061 --> 00:32:36.401
Then let's make that following that flow

568
00:32:36.423 --> 00:32:38.303
On Visual Studio

569
00:32:39.301 --> 00:32:42.580
go to NetTPSCharacter header file

570
00:32:43.920 --> 00:32:48.860
On the  very bottom, this was take pistol

571
00:32:52.420 --> 00:32:56.200
and now we're going to add release pistol down here

572
00:32:57.940 --> 00:33:02.241
UFUNCTION, we'll make the same thing

573
00:33:05.040 --> 00:33:11.603
UFUNCTION, void ServerRPC_ and this time

574
00:33:11.603 --> 00:33:15.363
ReleasePistol

575
00:33:18.501 --> 00:33:22.280
It's the same as take pistol

576
00:33:22.280 --> 00:33:27.321
On release pistol as well, I'll add implementation

577
00:33:31.641 --> 00:33:37.501
I'll cut ServerRPC ReleasePistol

578
00:33:37.501 --> 00:33:41.800
and put it under the ReleasePistol function

579
00:33:45.100 --> 00:33:51.460
just to make it easier to work with

580
00:33:56.303 --> 00:34:00.703
If on this ReleasePistol, one doesn't have a pistol attached

581
00:34:00.703 --> 00:34:03.600
or reloading it, the logic is not performed

582
00:34:03.601 --> 00:34:06.520
and this is done by the client

583
00:34:06.520 --> 00:34:09.201
The server only changes data

584
00:34:09.202 --> 00:34:11.461
Where is that? It's right here

585
00:34:11.461 --> 00:34:13.861
When one has a pistol

586
00:34:13.861 --> 00:34:15.841
Where should we put this

587
00:34:15.841 --> 00:34:20.200
We'll cut this and paste it here on ServerRPC

588
00:34:23.600 --> 00:34:25.900
And on ReleasePistol

589
00:34:27.600 --> 00:34:31.880
the request will be ServerRPC ReleasePistol

590
00:34:35.000 --> 00:34:37.550
Do you get the flow?

591
00:34:37.550 --> 00:34:41.650
Here, client

592
00:34:41.650 --> 00:34:43.900
ReleasePistol is client

593
00:34:43.900 --> 00:34:45.423
On the client side

594
00:34:45.423 --> 00:34:49.323
only the input is here

595
00:34:49.323 --> 00:34:50.961
Only the input

596
00:34:50.961 --> 00:34:55.483
And then after that, from here to where?

597
00:34:55.483 --> 00:34:56.483
To the server

598
00:34:58.183 --> 00:35:01.183
It requests using server RPC

599
00:35:01.183 --> 00:35:05.240
It sends a ReleasePistol request

600
00:35:05.240 --> 00:35:10.342
Then the server receives that

601
00:35:10.343 --> 00:35:11.722
and does this part

602
00:35:11.722 --> 00:35:14.501
This is not done by the client but where?

603
00:35:14.501 --> 00:35:17.801
On the server, this logic

604
00:35:21.903 --> 00:35:24.201
And the action of releasing the pisstol

605
00:35:24.201 --> 00:35:27.501
DetachPistol is done where?

606
00:35:27.502 --> 00:35:28.902
On the client side

607
00:35:28.902 --> 00:35:30.802
So the server again

608
00:35:30.802 --> 00:35:34.181
sends a message to the client

609
00:35:36.561 --> 00:35:40.203
That's how it goes

610
00:35:40.203 --> 00:35:43.143
So we implemented this on the server

611
00:35:44.443 --> 00:35:46.623
And when the server does this

612
00:35:46.623 --> 00:35:50.120
This DetachPistol is not done in the server

613
00:35:50.121 --> 00:35:52.720
but by the client

614
00:35:52.721 --> 00:35:55.800
So to make that happen

615
00:35:55.800 --> 00:36:01.360
I'll add a code that sends NetMulticastRPC to clients

616
00:36:01.363 --> 00:36:02.983
Let's make a funciton

617
00:36:03.700 --> 00:36:08.120
Go to NetTPSCharacter header file and on the bottom

618
00:36:09.163 --> 00:36:12.443
copy this function we made on take pistol

619
00:36:12.443 --> 00:36:15.803
and paste it

620
00:36:15.803 --> 00:36:19.303
Then instead of TakePistol we'll make it

621
00:36:19.303 --> 00:36:20.560
ReleasePistol

622
00:36:25.563 --> 00:36:29.183
Then on the parameter, the code that

623
00:36:29.183 --> 00:36:32.200
detaches the pistol from the hand will perfrom

624
00:36:32.200 --> 00:36:34.450
We declared one function

625
00:36:34.450 --> 00:36:37.743
and now let's implement NetMulticastRPC

626
00:36:37.743 --> 00:36:43.103
On the cpp file, we'll add that function's implementation

627
00:36:44.543 --> 00:36:48.420
then there's ServerRPC and NetMulticastRPC

628
00:36:51.603 --> 00:36:56.023
DetachPistol goes where?

629
00:36:56.023 --> 00:36:58.841
It goes to MulticastRPC

630
00:37:00.023 --> 00:37:06.263
and then MulticastRPC call is done by ServerRPC

631
00:37:06.263 --> 00:37:09.920
Then there will be internal communication as I told you

632
00:37:10.880 --> 00:37:13.501
Then the client

633
00:37:15.563 --> 00:37:18.623
requested to the server using server RPC

634
00:37:19.703 --> 00:37:21.953
After the server has done its job

635
00:37:21.953 --> 00:37:24.900
it will use NetMulticast to request back to the clients

636
00:37:27.721 --> 00:37:32.601
and make them perfrom this code

637
00:37:32.601 --> 00:37:33.901
Do you get it?

638
00:37:35.961 --> 00:37:37.821
Great

639
00:37:37.822 --> 00:37:42.321
Then we need to put the parameter value for NetMulticastRPC

640
00:37:42.321 --> 00:37:45.361
Which one? ownedPistol

641
00:37:47.923 --> 00:37:52.663
Then the owned pistol is sent to network

642
00:37:52.663 --> 00:37:56.901
and it will receive this and the pistol will be detached

643
00:37:58.241 --> 00:37:59.741
The server will send that

644
00:37:59.741 --> 00:38:03.440
and reset all owner settings

645
00:38:07.823 --> 00:38:08.823
Great

646
00:38:08.823 --> 00:38:12.223
Again, if we play this it will crash

647
00:38:12.223 --> 00:38:13.203
Why?

648
00:38:13.203 --> 00:38:18.561
Because again on DetachPistol, it calls ShowCrosshair

649
00:38:18.561 --> 00:38:24.120
On mainUI, it will be there for the client itself

650
00:38:24.121 --> 00:38:28.800
but it also shows to other characters' screens

651
00:38:28.801 --> 00:38:31.220
That character has mainUI or no?

652
00:38:31.220 --> 00:38:36.100
It hasn't, why? Because it is made only under the condition that player controller exists

653
00:38:36.101 --> 00:38:40.080
So here, we make it not happen when there's no mainUI

654
00:38:40.080 --> 00:38:45.323
if IsLocallyControlled

655
00:38:45.323 --> 00:38:48.283
and only when there's a mainUI character

656
00:38:50.041 --> 00:38:54.460
we need to change this part so that it will be performed only in that case

657
00:38:54.460 --> 00:38:57.481
This is the same as AttachPistol

658
00:38:58.763 --> 00:39:00.743
Let's build

659
00:39:07.481 --> 00:39:11.531
Then let's run the server

660
00:39:11.531 --> 00:39:13.141
and a client

661
00:39:14.601 --> 00:39:20.200
Take a pistol, it works, and let me release it with Z

662
00:39:24.321 --> 00:39:28.280
Then there's another error, Null Point Exception

663
00:39:28.280 --> 00:39:34.083
There's an error on the character's 227th line of ReleasePistol

664
00:39:34.083 --> 00:39:35.743
What is it?

665
00:39:37.103 --> 00:39:39.521
I didn't put pistolActor

666
00:39:39.521 --> 00:39:42.321
put just copy pasted DetachPistol

667
00:39:42.322 --> 00:39:44.201
so it says ownedPistol

668
00:39:44.201 --> 00:39:48.560
We'll put pistolActor here

669
00:39:48.561 --> 00:39:51.011
Why? Because if it says ownedPistol

670
00:39:51.011 --> 00:39:53.480
this one needs to release the one it got from the server

671
00:39:53.480 --> 00:39:57.680
so it might try to release the ownedPistol which it doesn't even posess

672
00:39:57.681 --> 00:39:59.930
which might cause an error

673
00:39:59.930 --> 00:40:05.760
So we need to make it detach the data it got from here

674
00:40:05.760 --> 00:40:08.710
Only then this value will be processed properly

675
00:40:08.710 --> 00:40:09.741
Let's build again

676
00:40:21.523 --> 00:40:25.023
and play with a client added

677
00:40:25.023 --> 00:40:28.283
F, take pistol

678
00:40:28.284 --> 00:40:30.063
Z, release

679
00:40:30.063 --> 00:40:32.161
You can see the pistol falls to the ground

680
00:40:32.161 --> 00:40:37.283
Again, F, maybe release it here

681
00:40:37.283 --> 00:40:40.543
I released it here on a hill

682
00:40:41.481 --> 00:40:44.441
Here's the pistol

683
00:40:44.442 --> 00:40:47.841
From the client side, let's see if the pistol is indeed there

684
00:40:47.841 --> 00:40:49.340
Aha, it's here

685
00:40:51.583 --> 00:40:57.223
Let me try the same thing on the client side

686
00:40:57.224 --> 00:41:00.443
Put it down here

687
00:41:00.443 --> 00:41:03.920
It's being synced well

688
00:41:08.501 --> 00:41:10.761
But there's something I want to show you

689
00:41:12.423 --> 00:41:16.523
Let's see the pistol placement on the client's screen and the server screen

690
00:41:16.523 --> 00:41:20.321
On the client's screen, the one on the left

691
00:41:20.321 --> 00:41:23.480
It shows that the pistol is here

692
00:41:25.163 --> 00:41:28.163
And let's see the right screen

693
00:41:28.163 --> 00:41:30.841
On the server screen, where is the pistol?

694
00:41:34.260 --> 00:41:36.461
It's at a different spot

695
00:41:38.203 --> 00:41:40.003
So in the server, the pistol is here

696
00:41:40.003 --> 00:41:41.543
but it's somewhere different for the client

697
00:41:41.543 --> 00:41:43.440
This is an error

698
00:41:44.443 --> 00:41:47.883
So even when the server wants to take the pistol

699
00:41:47.883 --> 00:41:49.033
when performing that logic

700
00:41:49.033 --> 00:41:50.880
it's here for the client so even if it tries to take it

701
00:41:50.880 --> 00:41:53.130
if it's somewhere random

702
00:41:53.130 --> 00:41:55.220
then it can't take it

703
00:41:55.221 --> 00:41:57.640
because on the server, it says that it's here

704
00:41:57.640 --> 00:42:01.800
The location data isn't being synced

705
00:42:01.800 --> 00:42:04.481
Then what should we do

706
00:42:04.482 --> 00:42:08.321
We can activate Actor Replication that we learned

707
00:42:08.321 --> 00:42:11.421
There's this BP Pistol

708
00:42:11.421 --> 00:42:14.943
There's BP Pistol on NetTPS Blueprint

709
00:42:14.943 --> 00:42:16.223
Open this

710
00:42:17.401 --> 00:42:22.280
and let me search Replicate on BP Pistol's detail window

711
00:42:22.281 --> 00:42:25.380
Search Replicate

712
00:42:25.380 --> 00:42:27.230
and you'll see Replicate Movement

713
00:42:27.230 --> 00:42:28.860
and Replicate

714
00:42:28.860 --> 00:42:31.410
These aren't activated

715
00:42:31.410 --> 00:42:33.400
so it is not being synced

716
00:42:33.401 --> 00:42:35.760
So check on Replicate option

717
00:42:35.760 --> 00:42:38.704
and Replicate Movement as well

718
00:42:38.704 --> 00:42:42.004
and then the values on movements, within Unreal Engine

719
00:42:42.004 --> 00:42:43.104
will be synced

720
00:42:45.384 --> 00:42:49.104
If you say that you'll replicate, network sync

721
00:42:49.104 --> 00:42:52.040
on Blueprint, it automatically does that

722
00:42:52.040 --> 00:42:56.361
'Then on C++, not only that but

723
00:42:56.362 --> 00:42:57.862
property value needs to be synced

724
00:42:57.862 --> 00:43:02.024
and Get Lifetime Replicated, all these need to be done too'

725
00:43:02.024 --> 00:43:02.664
Right

726
00:43:04.264 --> 00:43:06.164
These parts too

727
00:43:06.164 --> 00:43:08.884
But on Blueprint, that part ins't needed

728
00:43:08.884 --> 00:43:10.860
It's simpler on Blueprint

729
00:43:10.861 --> 00:43:14.280
But when making these network codes and logic

730
00:43:14.280 --> 00:43:17.361
it's more efficient to work on C++

731
00:43:17.361 --> 00:43:19.811
It helps with management too

732
00:43:19.811 --> 00:43:22.900
but Blueprint has an easier structure

733
00:43:24.324 --> 00:43:26.544
Of course, when working on RPC and such

734
00:43:26.544 --> 00:43:28.024
if you keep going back and forth with Blueprint

735
00:43:28.024 --> 00:43:30.760
you can get very confused with the logic

736
00:43:30.760 --> 00:43:35.081
So usually, C++ does all of the network

737
00:43:36.241 --> 00:43:40.001
But here, the pistol ins't being synced

738
00:43:40.002 --> 00:43:43.721
so I just used these two Replicate options in the detail window

739
00:43:43.721 --> 00:43:47.860
to sync this pistol actor

740
00:43:49.160 --> 00:43:52.080
Let's go back and play

741
00:43:55.144 --> 00:43:59.344
Go, and Z, released

742
00:43:59.344 --> 00:44:03.520
Then for the server, it's on the ground

743
00:44:03.520 --> 00:44:05.320
From the client as well

744
00:44:05.320 --> 00:44:07.480
it's on the ground

745
00:44:07.481 --> 00:44:11.660
F, let's drop it somewhere else

746
00:44:11.660 --> 00:44:15.301
and the two on network

747
00:44:15.302 --> 00:44:18.142
are being synced

748
00:44:18.142 --> 00:44:20.441
The same location

749
00:44:20.441 --> 00:44:24.160
You can test this further

750
00:44:25.184 --> 00:44:28.964
and Blueprint can very simply

751
00:44:28.964 --> 00:44:30.864
sync movement

752
00:44:30.864 --> 00:44:33.561
and location value

753
00:44:33.561 --> 00:44:35.761
by activating Replicate options

754
00:44:35.761 --> 00:44:38.841
on network

755
00:44:38.842 --> 00:44:41.801
That will be it

756
00:44:41.801 --> 00:44:44.721
This was release pistol

757
00:44:46.481 --> 00:44:49.240
Let's summarize what we've learned in this unit

758
00:44:50.592 --> 00:44:51.592
Take pistol
RPC communication

759
00:44:51.593 --> 00:44:52.484
User only performs input and the logic is performed in the server using server RPC

760
00:44:52.485 --> 00:44:53.364
NetMulticast is used together to perform animation and visualization on all clients

761
00:44:53.365 --> 00:44:56.124
UI
It must work only on clients
Needs a logic to separate UI

762
00:44:56.125 --> 00:44:57.349
Animation
Uses property replication

763
00:44:57.349 --> 00:44:58.709
Release pistol
RPC communication

764
00:44:58.710 --> 00:45:01.729
Requests to server to release pistol using server RPC
Uses NetMulticast RPC to send result to all clients

765
00:45:01.729 --> 00:45:02.729
The End