UE5- c++ websocket客户端写法

# 实现目标

ue5 c++ 实现socket客户端，读取服务端数据，并进行解析

#实现步骤

{projectName}.Build.cs里增加 "WebSockets","JsonUtilities", "Json"配置信息，最终输出如下：

using UnrealBuildTool;

public class myue521 : ModuleRules
{
	public myue521(ReadOnlyTargetRules Target) : base(Target)
	{
		PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;

		PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore"
        , "HeadMountedDisplay", "EnhancedInput"
        , "WebSockets","JsonUtilities", "Json"});
	}
}

说明，其中myue521是我的模块名，文件名为myue521.Build.cs。新增的模块："WebSockets","JsonUtilities", "Json"。

准备实现自己的webscoket_client。具体操作步骤如下：

在ue5中自定义类，父类设置为UGameInstance,我这命名为UUWebSocketGameInstance
在UUWebSocketGameInstance.h里新增如下方法。
1. 其中init和 Shutdown方法是在父类UGameInstance中定义的，我们这里覆盖它；
2. WebSocket用来标识我们代码生成的socket，计划在init里初始化，在Shutdown里销毁
3. OnConnected、OnConnectionError、OnClosed、OnMessage、OnMessageSent用来处理socket消息，具体看后买你的代码实现。

在UUWebSocketGameInstance.cpp里实现已经生命的方法。

// Fill out your copyright notice in the Description page of Project Settings.


#include "UWebSocketGameInstance.h"
#include "WebSockets/Public/WebSocketsModule.h"
#include "WebSockets/Public/IWebSocket.h"
#include "Templates/SharedPointer.h"


void UUWebSocketGameInstance::Init() {
	Super::Init();

	if (!FModuleManager::Get().IsModuleLoaded("WebSockets")) {
		FModuleManager::Get().LoadModule("WebSockets");
	}

	WebSocket = FWebSocketsModule::Get().CreateWebSocket("ws://127.0.0.1:8081/webSocketServer/ue");
	 
	WebSocket->OnConnected().AddUObject(this, &UUWebSocketGameInstance::OnConnected);
	WebSocket->OnConnectionError().AddUObject(this, &UUWebSocketGameInstance::OnConnectionError);
	WebSocket->OnClosed().AddUObject(this, &UUWebSocketGameInstance::OnClosed);
	WebSocket->OnMessage().AddUObject(this, &UUWebSocketGameInstance::OnMessage);
	WebSocket->OnMessageSent().AddUObject(this, &UUWebSocketGameInstance::OnMessageSent);

	WebSocket->Connect();

}
 

void UUWebSocketGameInstance::Shutdown() {

	if (WebSocket->IsConnected()) {
		WebSocket->Close();
	} 
	Super::Shutdown();
}



void UUWebSocketGameInstance::OnConnected()
{
	UE_LOG(LogTemp, Warning, TEXT("%s"), *FString(__FUNCTION__));

	GEngine->AddOnScreenDebugMessage(-1, 3.0f, FColor::Green, "Successfully Connected");
}

void UUWebSocketGameInstance::OnConnectionError(const FString& Error)
{
	UE_LOG(LogTemp, Warning, TEXT("%s Error:%s"), *FString(__FUNCTION__), *Error);
}

void UUWebSocketGameInstance::OnClosed(int32 StatusCode, const FString& Reason, bool bWasClean)
{
	UE_LOG(LogTemp, Warning, TEXT("%s StatusCode:%d Reason:%s bWasClean:%d"),
		*FString(__FUNCTION__), StatusCode, *Reason, bWasClean);
}

void UUWebSocketGameInstance::OnMessage(const FString& Message)
{
	GEngine->AddOnScreenDebugMessage(-1, 3.0f, FColor::Cyan, FString::Printf(TEXT("%s Message:%s"), *FString(__FUNCTION__), *Message) );

	UE_LOG(LogTemp, Warning, TEXT("%s Message:%s"), *FString(__FUNCTION__), *Message);

	TSharedRef< TJsonReader<> > Reader = TJsonReaderFactory<>::Create(Message);
	TSharedPtr<FJsonObject> Root;

	if (FJsonSerializer::Deserialize(Reader, Root))
	{
		if (Root->HasField(TEXT("Topic"))) {
			FString Topic = Root->GetStringField(TEXT("Topic"));
			TSharedPtr<FJsonObject, ESPMode::ThreadSafe> Data = Root->GetObjectField(TEXT("Data"));

			// TSharedPtr<FJsonObject, ESPMode::ThreadSafe> ObjectField = Object->GetObjectField(TEXT("realtime"));
			FString KeyField = Data->GetStringField("Key");
			FString ValueField = Data->GetStringField("Value");


			GEngine->AddOnScreenDebugMessage(-1, 3.0f, FColor::Cyan, "Key: " + KeyField + ",Value:" + ValueField);
		}
		else {
			GEngine->AddOnScreenDebugMessage(-1, 3.0f, FColor::Cyan, "解析json异常");
		}
	}
}

void UUWebSocketGameInstance::OnMessageSent(const FString& MessageString)
{
	UE_LOG(LogTemp, Warning, TEXT("%s MessageString:%s"), *FString(__FUNCTION__), *MessageString);
}

其中UUWebSocketGameInstance::Init()里初始化了websocket,并配置监听方法
UUWebSocketGameInstance::Shutdown()用来销毁生成的websocket
UUWebSocketGameInstance::OnConnected（），UUWebSocketGameInstance::OnConnectionError，UUWebSocketGameInstance::OnClosed，UUWebSocketGameInstance::OnMessage，UUWebSocketGameInstance::OnMessageSent是用来处理绑定消息的。其中UUWebSocketGameInstance::OnMessage里的消息是json格式，具体格式见下面的备注1.

开始配置使用并调用方法。

自主调用可以在某个Character里通过如下代码进行调用。可以在自己的类里面调用。比如放到构造方法或者某个动作触发调用。

void Amyue521Character::NotifyServer() {
	UUWebSocketGameInstance* GameInstance = Cast<UUWebSocketGameInstance>(GetGameInstance());
	if (GameInstance) {
		if (GameInstance->WebSocket->IsConnected()) {
			GameInstance->WebSocket->Send("FROM UnrealEngine 5");
		}
	}
}

通过UE5的项目设置进行修改游戏实例。

备注

约定接收的json数据格式为

{
    "Topic": "Unreal",
    "Data": {
        "Key": "mood",
        "Value": 1.0
    }
 }

总结

通过该例子我们学到了websocket,json的应用

还学到的两种打印log的方法

GEngine->AddOnScreenDebugMessage(-1, 3.0f, FColor::Cyan, FString::Printf(TEXT("%s Message:%s"), *FString(__FUNCTION__), *Message) );

UE_LOG(LogTemp, Warning, TEXT("%s Message:%s"), *FString(__FUNCTION__), *Message);