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。
1. 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");}}
}
```
2. 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);