本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。

設定遠端裝置並使用 IoT 代理程式

IoT 代理程式用來接收包含用戶端存取字符的 MQTT 訊息，並在遠端裝置上啟動本機代理。如果您想要安全通道使用 MQTT 交付用戶端存取字符，則必須在遠端裝置上安裝並執行 IoT 代理程式。IoT 代理程式必須訂閱下列保留的 IoT MQTT 主題：

IoT Agent Snippet

IoT 代理程式必須訂閱下列保留的 IoT MQTT 主題，才能接收 MQTT 訊息並啟動本機 Proxy：

$aws/things/thing-name/tunnels/notify

哪裡thing-name是與遠端裝置相 AWS IoT 關聯的物件名稱。

以下是 MQTT 訊息酬載的範例：

{
    "clientAccessToken": "destination-client-access-token",
    "clientMode": "destination",
    "region": "aws-region",
    "services": ["destination-service"]
}

在收到 MQTT 訊息之後，IoT 代理程式必須使用適當的參數，在遠端裝置上啟動本機代理。

下列 Java 程式碼示範如何使用AWS IoT 裝置 SDK 和 Java 程式庫ProcessBuilder來建置簡單的 IoT 代理程式以使用安全通道。

// Find the IoT device endpoint for your AWS 帳戶
final String endpoint = iotClient.describeEndpoint(new DescribeEndpointRequest().withEndpointType("iot:Data-ATS")).getEndpointAddress();

// Instantiate the IoT Agent with your AWS credentials
final String thingName = "RemoteDeviceA";
final String tunnelNotificationTopic = String.format("$aws/things/%s/tunnels/notify", thingName);
final AWSIotMqttClient mqttClient = new AWSIotMqttClient(endpoint, thingName,
                 "your_aws_access_key", "your_aws_secret_key");

try {
    mqttClient.connect();
    final TunnelNotificationListener listener = new TunnelNotificationListener(tunnelNotificationTopic);
    mqttClient.subscribe(listener, true);
}
finally {
    mqttClient.disconnect();
}

private static class TunnelNotificationListener extends AWSIotTopic {
    public TunnelNotificationListener(String topic) {
        super(topic);
    }

    @Override
    public void onMessage(AWSIotMessage message) {
        try {
            // Deserialize the MQTT message
            final JSONObject json = new JSONObject(message.getStringPayload());
 
            final String accessToken = json.getString("clientAccessToken");
            final String region = json.getString("region");
            
            final String clientMode = json.getString("clientMode");
            if (!clientMode.equals("destination")) {
                throw new RuntimeException("Client mode " + clientMode + " in the MQTT message is not expected");
            }

            final JSONArray servicesArray = json.getJSONArray("services");
            if (servicesArray.length() > 1) {
                throw new RuntimeException("Services in the MQTT message has more than 1 service");
            }
            final String service = servicesArray.get(0).toString();
            if (!service.equals("SSH")) {
                throw new RuntimeException("Service " + service + " is not supported");
            }

            // Start the destination local proxy in a separate process to connect to the SSH Daemon listening port 22
            final ProcessBuilder pb = new ProcessBuilder("localproxy",
                        "-t", accessToken,
                        "-r", region,
                        "-d", "localhost:22");
            pb.start();
        }
        catch (Exception e) {
            log.error("Failed to start the local proxy", e);
        }
    }
}