Amazon GameLift StreamsのデータチャネルでUnityアプリとWebクライアントを連携させてみた

{"type":"ready"}
{"type":"state","counterA":5,"counterB":3}

{"type":"command","action":"reset","target":"counterA"}
{"type":"command","action":"set","target":"counterA","value":42}
{"type":"command","action":"resetAll"}

public class DataChannelHandler : MonoBehaviour
{
    [SerializeField] private string host = "localhost";
    [SerializeField] private int port = 40712;
    [SerializeField] private float reconnectInterval = 3f;
    [SerializeField] private ButtonCounter buttonCounter;

    private TcpClient _tcp;
    private NetworkStream _stream;
    private Thread _readThread;
    private volatile bool _connected;
    private volatile bool _running;
    private volatile byte _clientId;

    // メインスレッドで実行するアクションのキュー
    private readonly ConcurrentQueue<Action> _mainThreadActions = new();

    void Start()
    {
        if (buttonCounter != null)
            buttonCounter.OnCountChanged += OnCountChanged;

        _running = true;
        _readThread = new Thread(ReadLoop) { IsBackground = true };
        _readThread.Start();
    }

    void Update()
    {
        // バックグラウンドスレッドからのアクションをメインスレッドで実行
        while (_mainThreadActions.TryDequeue(out var action))
            action.Invoke();
    }
}

private bool SendString(string message)
{
    if (!_connected || _stream == null || !_stream.CanWrite)
        return false;

    var data = Encoding.UTF8.GetBytes(message);
    var header = new byte[4];
    header[0] = _clientId;
    header[1] = 2; // イベントタイプ = メッセージ
    header[2] = (byte)(data.Length >> 8);
    header[3] = (byte)(data.Length & 0xFF);

    lock (_stream)
    {
        _stream.Write(header, 0, 4);
        if (data.Length > 0)
            _stream.Write(data, 0, data.Length);
        _stream.Flush();
    }
    return true;
}

private void HandleMessage(string json)
{
    var msg = JsonUtility.FromJson<IncomingMessage>(json);

    if (msg.type != "command") return;

    switch (msg.action)
    {
        case "reset":
            buttonCounter.ResetCounter(msg.target);
            break;
        case "set":
            buttonCounter.SetCounter(msg.target, msg.value);
            break;
        case "resetAll":
            buttonCounter.ResetAll();
            break;
    }
}

[Serializable]
private class IncomingMessage
{
    public string type;
    public string action;
    public string target;
    public int value;
}

/**
 * アプリケーションにコマンドを送信する。
 * @param {Object} command - 送信するJSONコマンドオブジェクト
 */
function dataChannelSendCommand(command) {
    if (!window.myGameLiftStreams) {
        console.warn('GameLiftStreams not initialized');
        return;
    }
    const json = JSON.stringify(command);
    const encoded = new TextEncoder().encode(json);
    window.myGameLiftStreams.sendApplicationMessage(encoded);
}

// カウンターをリセット
function dcResetCounter(target) {
    dataChannelSendCommand({ type: 'command', action: 'reset', target: target });
}

// 全カウンターをリセット
function dcResetAll() {
    dataChannelSendCommand({ type: 'command', action: 'resetAll' });
}

// カウンターに値を設定
function dcSetCounter(target) {
    const value = parseInt(document.getElementById('dcSetValueA').value, 10);
    dataChannelSendCommand({ type: 'command', action: 'set', target: target, value: value });
}

/**
 * アプリケーションからのバイナリメッセージを受信して処理する。
 * @param {Uint8Array} message - データチャネル経由で受信したバイト配列
 */
function streamApplicationMessageCallback(message) {
    try {
        // バイト配列をUTF-8 JSON文字列にデコード
        const text = new TextDecoder('utf-8').decode(message);
        const data = JSON.parse(text);

        if (data.type === 'ready') {
            // アプリケーション側の準備完了
            document.getElementById('dcStatus').textContent = 'Connected';
            document.getElementById('dcStatus').style.color = '#4CAF50';
        } else if (data.type === 'state') {
            // カウンター状態の更新
            document.getElementById('dcCounterA').textContent = data.counterA;
            document.getElementById('dcCounterB').textContent = data.counterB;
        }
    } catch (e) {
        console.error('Failed to parse application message:', e);
    }
}

const clientConnection = {
    // ... 他の設定 ...
    applicationMessage: streamApplicationMessageCallback,
};

window.myGameLiftStreams = new GameLiftStreams({
    clientConnection: clientConnection,
});