client plugin for Unreal Engine 4
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Latest commit 7303720 Jul 13, 2018

socketio-client-ue4 client plugin for UE4.

GitHub release Github All Releases is a performant real-time bi-directional communication library. There are two parts, the server written in node.js and the client typically javascript for the web. There are alternative client implementations and this repo uses the C++11 client library ported to UE4.

Based on prebuild libraries for VS2015 and SIOJson forked from ufna's VaRest

Unreal Forum Thread

Recommended server version: 1.4+.

Contribute! Current Issues:

Missing static libraries and support for platforms:

Quick Install & Setup

  1. Download Latest Release
  2. Create new or choose project.
  3. Browse to your project folder (typically found at Documents/Unreal Project/{Your Project Root})
  4. Copy Plugins folder into your Project root.
  5. Plugin should be now ready to use.

Optional Plugin Enabled Check

  1. If your plugin isn't enabled for whatever reason you can enable the plugin via Edit->Plugins. Scroll down to Project->Networking. Click Enabled.
  2. Restart the Editor and open your project again. Plugin is now ready to use.

Example Project - Chat

For an example project check out which contains both server and client parts required to try out based chat, from UE4 to any other client and vice versa.

How to use - BP Basics

Add the SocketIO Client Component to your blueprint actor of choice


By default the component will auto connect on begin play to your default address and port http://localhost:3000. You can change this default address to connect to your service instead.


If you want to connect at your own time, you change the default variable Should Auto Connect to false and then call Connect with your address

Call Bind Event for each event you wish the client to subscribe, e.g. 'chat message'

If you expect to receive events, select your component and in the Details pane press the + to add an 'OnEvent' event to your event graph

Handle this event for your event types, e.g. printing 'chat message' event strings.


If you want to send information to the server, emit events on the SocketIO Client Component, e.g. pressing M to emit a 'chat message' string


Blueprint - Advanced

Simple Json

You can formulate any SIOJsonValue directly in blueprint. Apart from native basic types which are supported directly via conversion and e.g. Construct Json String Value, you can construct SIOJsonObjects and fill their fields.


Start with Construct Json Object then set any desired fields. In this instance we wanted to make the JSON {"myString":"Hello"} so we used Set String Field and then auto-convert the object into a message.

Complex Json

By combining arrays and objects you can form almost any data type, nest away!



The plugin supports making SIOJsonValues from any unreal structs you make, including ones defined purely in blueprints!

An easy example of a familiar struct is the Vector type


But you can make a custom type and emit it or nest it inside other SIOJsonValues which should make it easy to organize your data however you want it.



Socket.IO spec supports raw binary data types and these should be capable of being mixed in with other JSON types as usual. This plugin supports binaries as a first class citizen in blueprints and any arrays of bytes can be embedded and decoded in the chain as expected.


Decoding Responses

There are many ways to decode your SIOJsonValue message, it all depends on your data setup. You can even decode your JsonObjects directly into structs, if the JSON structure has matching variable names.



Most primitive types have auto-conversion nodes to simplify your workflow. E.g. if you wanted to emit a float literal you can get a reference to your float and simply drag to the message parameter to auto-convert into a SIOJsonValue.


Supported auto-conversion

  • Float
  • Int
  • Bool
  • String
  • SIOJsonObject
  • Emit with Callback

    You can have a callback when, for example, you need an acknowledgement or if you're fetching data from the server. You can respond to this callback straight in your blueprint.


    Instead of using Emit you use Emit With Callback and by default the target is the owning actor blueprint so you can leave that parameter blank and simply type your function name e.g. OnEcho function.


    If the function is missing or named incorrectly, your output log will warn you.


    Your function expects a SIOJsonValue reference signature. By default this contains your first response value from you callback parameter. If your callback uses more than one parameter, make a second SIOJsonValue Input parameter which contains an array of all the responses.

    Since 0.6.8, if you know your data type you can use that signature directly in your function name. E.g. if you're sending a callback with a float value you can make a function with the matching name and only one float parameter as your signature.

    Supported Signatures:

    • SIOJsonValue
    • SIOJsonObject
    • String
    • Float
    • Int
    • Bool
    • Byte Array

    Binding Events to Functions

    Instead of using the event graph and comparing strings, you can bind an event directly to a function. The format to make the function is the same as callbacks.


    Complex Connect

    You can fill the optional Query and Headers parameters to pass in e.g. your own headers for authentication.

    The input type for both fields is a SIOJsonObject with purely string fields or leaving it empty for default.

    Here's an example of constructing a single header X-Forwarded-Host: and then connecting.


    Plugin Scoped Connection

    If you want your connection to survive level transitions, you can tick the class default option Plugin Scoped Connection. Then if another component has the same plugin scoped id, it will re-use the same connection. Note that if this option is enabled the connection will not auto-disconnect on End Play and you will need to either manually disconnect or the connection will finally disconnect when the program exits.

    plugin scoped connection

    This does mean that you may not receive events during times your actor does not have a world (such as a level transition without using a persistent parent map to which the component actor belongs). If this doesn't work for you consider switching to C++ and using FSocketIONative, which doesn't doesn't depend on using an actor component.

    How to use - C++


    To use the C++ code from the plugin add it as a dependency module in your project build.cs

    PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "SocketIOClient"});

    This guide assumes you want to use the client component method. See the FSocketIONative section for non-actor based C++ details.

    #include "SocketIOClientComponent.h" and add USocketIoClientComponent to your actor of choice via e.g. a UProperty

    and CreateDefaultSubobject in your constructor

    SIOClientComponent = CreateDefaultSubobject<USocketIOClientComponent>(TEXT("SocketIOClientComponent"));

    or reference it from another component by getting it on begin play e.g.

    SIOClientComponent = Cast<USocketIOClientComponent>(this->GetOwner()->GetComponentByClass(USocketIOClientComponent::StaticClass()));
    if (!SIOClientComponent)
    	UE_LOG(LogTemp, Warning, TEXT("No sister socket IO component found"));
    	UE_LOG(LogTemp, Log, TEXT("Found SIOClientComponent: %s"), *SIOComponent->GetDesc());

    Connect / Disconnect

    To connect simply change your address, the component will auto-connect on component initialization.

    USocketIOClientComponent* SIOClientComponent; //get a reference or add as subobject in your actor
    //the component will autoconnect, but you may wish to change the url before it does that via
    SIOClientComponent->AddressAndPort = FString(""); //change your address

    You can also connect at your own time by disabling auto-connect and connecting either to the default address or a custom one

    //you can also disable auto connect and connect it at your own time via
    SIOClientComponent->ShouldAutoConnect = false;
    //You can also easily disconnect at some point, reconnect to another address

    Receiving Events

    To receive events call OnNativeEvent and pass in your expected event name and callback lambda or function with void(const FString&, const TSharedPtr<FJsonValue>&) signature. Optionally pass in another FString to specify namespace, omit if not using a namespace.

    SIOClientComponent->OnNativeEvent(FString("MyEvent"), [](const FString& Event, const TSharedPtr<FJsonValue>& Message)
    	//Called when the event is received
    }, FString("Optional Namespace"));

    Emitting Events

    In C++ you can use EmitNative, EmitRaw, or EmitRawBinary. EmitNative is fully overloaded and expects all kinds of native UE4 data types and is the recommended method.


    Emit an FString. Note that FString(TEXT("yourString")) is recommended if you have performance concerns due to internal conversion from char*

    SIOClientComponent->EmitNative(FString("nativeTest"), FString("hi"));


    Emit a double

    SIOClientComponent->EmitNative(FString("nativeTest"), -3.5f);


    Emit a raw boolean

    SIOClientComponent->EmitNative(FString("nativeTest"), true);

    Binary or raw data

    Emit raw data via a TArray

    TArray<uint8> Buffer;	//null terminated 'Hi!'
    SIOClientComponent->EmitNative(FString("nativeTest"), Buffer);


    SIOComponent->EmitRawBinary(FString("myBinarySendEvent"), Buffer.GetData(), Buffer.Num());

    FJsonObject - Simple

    Option 1 - Shorthand

    //Basic one field object e.g. {"myKey":"myValue"}
    auto JsonObject = USIOJConvert::MakeJsonObject();								
    JsonObject->SetStringField(FString("myKey"), FString("myValue"));
    SIOClientComponent->EmitNative(FString("nativeTest"), JsonObject);

    Option 2 - Standard

    TSharedPtr<FJsonObject> JsonObject = MakeShareable(new FJsonObject);	

    FJsonObject - Complex Example

    A nested example using various methods

    //All types, nested
    TSharedPtr<FJsonObject> JsonObject = MakeShareable(new FJsonObject);						//make object option2
    JsonObject->SetBoolField(FString("myBool"), false);
    JsonObject->SetStringField(FString("myString"), FString(" is easy"));
    JsonObject->SetNumberField(FString("myNumber"), 9001);
    JsonObject->SetField(FString("myBinary1"), USIOJConvert::ToJsonValue(Buffer));				//binary option1 - shorthand
    JsonObject->SetField(FString("myBinary2"), MakeShareable(new FJsonValueBinary(Buffer)));	//binary option2
    JsonObject->SetArrayField(FString("myArray"), ArrayValue);
    JsonObject->SetObjectField(FString("myNestedObject"), SmallObject);
    SIOClientComponent->EmitNative(FString("nativeTest"), JsonObject);

    Callback Example

    Below is an example of emitting a simple object with the server using the passed in callback to return a response or acknowledgement.

    //Make an object {"myKey":"myValue"}
    TSharedPtr<FJsonObject> JsonObject = MakeShareable(new FJsonObject);
    JsonObject->SetStringField(FString("myKey"), FString("myValue"));
    //Show what we emitted
    UE_LOG(LogTemp, Log, TEXT("1) Made a simple object and emitted: %s"), *USIOJConvert::ToJsonString(JsonObject));
    //Emit event "callbackTest" expecting an echo callback with the object we sent
    SIOClientComponent->EmitNative(FString("callbackTest"), JsonObject, [&](auto Response)
    	//Response is an array of JsonValues, in our case we expect an object response, grab first element as an object.
    	auto Message = Response[0]->AsObject();
    	//Show what we received
    	UE_LOG(LogTemp, Log, TEXT("2) Received a response: %s"), *USIOJConvert::ToJsonString(Message));


    Plugin supports automatic conversion to/from UStructs, below is an example of a struct roundtrip, being in Json format on the server side.

    struct FTestCppStruct
    	int32 Index;
    	float SomeNumber;
    	FString Name;
    //Set your struct variables
    FTestCppStruct TestStruct;
    TestStruct.Name = FString("George");
    TestStruct.Index = 5;
    TestStruct.SomeNumber = 5.123f;
    SIOClientComponent->EmitNative(FString("callbackTest"),  FTestCppStruct::StaticStruct(), &TestStruct, [&](auto Response)
    	auto Message = Response[0]->AsObject();
    	//Show what we received
    	UE_LOG(LogTemp, Log, TEXT("Received a response: %s"), *USIOJConvert::ToJsonString(Message));
    	//Set our second struct to the new values
    	USIOJConvert::JsonObjectToUStruct(Message, FTestCppStruct::StaticStruct(), &MemberStruct);
    	//Show that struct
    	UE_LOG(LogTemp, Log, TEXT("Our received member name is now: %s"), *MemberStruct.Name);

    C++ FSocketIONative

    If you do not wish to use UE4 AActors or UObjects, you can use the native base class FSocketIONative. Please see the class header for API. It generally follows a similar pattern to USocketIOClientComponent with the exception of native callbacks which you can for example see in use here:

    Alternative Raw C++ Complex message using sio::message

    see sio::message for how to form a raw message. Generally it supports a lot of std:: variants e.g. std::string or more complex messages e.g. c++ emit readme. Note that there are static helper functions attached to the component class to convert from std::string to FString and the reverse.

    static std::string USIOMessageConvert::StdString(FString UEString);
    static FString USIOMessageConvert::FStringFromStd(std::string StdString);

    and assuming

    FSocketIONative* NativeClient;

    e.g. emitting {type:"image"} object

    //create object message
    auto message = sio::object_message::create();
    //set map property string
    message->get_map()["type"] = sio::string_message::create(std::string("image"));
    //emit message
    NativeClient->EmitRaw(ShareResourceEventName, message);

    with a callback

    NativeClient->EmitRawWithCallback(FString("myRawMessageEventWithAck"), string_message::create(username), [&](message::list const& msg) {
    	//got data, handle it here

    Receiving Events

    To receive events you can bind lambdas which makes things awesomely easy e.g.


    NativeClient->OnBinaryEvent([&](const FString& Name, const TArray<uint8>& Buffer)
    			//Do something with your buffer
    		}, FString(TEXT("myBinaryReceiveEvent")));

    Complex message using sio::message

    See sio::message or c++ readme for examples.

    e.g. expecting a result {type:"some type"}

    NativeClient->OnRawEvent([&](const FString& Name, const sio::message::ptr& Message)
    		        //if you expected an object e.g. {}
    			if (Message->get_flag() != sio::message::flag_object)
    				UE_LOG(LogTemp, Warning, TEXT("Warning! event did not receive expected Object."));
    			auto MessageMap = Message->get_map();
    			//use the map to decode an object key e.g. type string
    			auto typeMessage = MessageMap["type"];
    			if (typeMessage->get_flag() == typeMessage->flag_string)
    				FString TypeValue = USocketIOClientComponent::FStringFromStd(typeMessage->get_string());
    				//do something with your received type value!
    		}, FString(TEXT("myArbitraryReceiveEvent")));



    Works out of the box.


    If you're using this as a project plugin you will need to convert your blueprint only project to mixed (bp and C++). Follow these instructions to do that: