HarmonyOS NEXT（四）：设备互联与通信

企业开发 2025-04-08 10:21:24 阅读次数: 0

HarmonyOS NEXT（四）：设备互联与通信

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一、近场发现协议深度解析

1.1 多协议协同发现机制

// 多协议设备发现示例（ArkTS）
import {
    
     Connection, connection } from '@kit.ConnectivityKit';

class UnifiedDiscovery {
    
    
  private nfcAdapter: connection.NfcAdapter;
  private bleScanner: connection.BleScanner;
  private wifiP2p: connection.WifiP2p;

  constructor() {
    
    
    this.nfcAdapter = connection.createNfcAdapter();
    this.bleScanner = connection.createBleScanner();
    this.wifiP2p = connection.createWifiP2p();
  }

  startDiscovery() {
    
    
    // NFC贴靠触发
    this.nfcAdapter.on('tagDiscovered', (tag) => {
    
    
      this.handleNfcDevice(tag);
    });

    // BLE广播扫描
    this.bleScanner.startScan({
    
    
      filters: [{
    
     serviceUuid: '1827' }],
      scanMode: connection.ScanMode.LOW_LATENCY
    });

    // WiFi P2P发现
    this.wifiP2p.discoverPeers();
    this.wifiP2p.on('peerFound', (peer) => {
    
    
      this.handleWifiPeer(peer);
    });
  }

  private handleNfcDevice(tag: connection.NfcTag) {
    
    
    const deviceInfo = tag.readNdefMessage();
    this.establishConnection(deviceInfo);
  }
}

协议栈架构：

二、分布式软总线核心技术

2.1 端到端传输管道

// 软总线通道建立核心逻辑（C）
static int32_t BuildBusChannel(const BusAttribute *attribute) {
    
    
    int32_t ret;
    struct BusChannel *channel = CreateChannel(attribute->type);
    if (channel == NULL) {
    
    
        return SOFTBUS_ERR;
    }
    
    ret = channel->Init(channel, attribute);
    if (ret != SOFTBUS_OK) {
    
    
        DeleteChannel(channel);
        return ret;
    }
    
    ret = channel->Connect(channel);
    if (ret != SOFTBUS_OK) {
    
    
        channel->Close(channel);
        return ret;
    }
    
    AddToChannelMgr(channel);
    return SOFTBUS_OK;
}

// 消息传输接口
int32_t SendMessage(const char *deviceId, const uint8_t *data, uint32_t len) {
    
    
    struct BusChannel *channel = FindChannel(deviceId);
    if (channel == NULL) {
    
    
        return SOFTBUS_CHANNEL_NOT_EXIST;
    }
    return channel->Send(channel, data, len);
}

2.2 QoS保障策略

业务类型	延迟要求	带宽保障	重传策略
控制指令	<50ms	128Kbps	即时重传
语音传输	<100ms	64Kbps	有限次重传
视频流	<200ms	2Mbps	前向纠错
文件传输	无要求	最大带宽	校验重传

三、低时延音视频传输

3.1 实时传输协议栈

3.2 抗弱网优化方案

// 自适应传输策略（ArkTS）
class AdaptiveStreamer {
    
    
  private stats: NetworkStats;
  private readonly strategies = {
    
    
    excellent: {
    
     bitrate: 4000, fps: 60 },
    good: {
    
     bitrate: 2500, fps: 30 },
    poor: {
    
     bitrate: 1000, fps: 15 }
  };

  updateNetworkStats(stats: NetworkStats) {
    
    
    this.stats = stats;
    this.adjustStreamParams();
  }

  private adjustStreamParams() {
    
    
    const {
    
     packetLoss, rtt } = this.stats;
    
    if (packetLoss < 2% && rtt < 100) {
    
    
      this.applyStrategy('excellent');
    } else if (packetLoss < 5% && rtt < 200) {
    
    
      this.applyStrategy('good');
    } else {
    
    
      this.applyStrategy('poor');
    }
    
    this.enableFEC(packetLoss > 3%);
  }

  private enableFEC(enable: boolean) {
    
    
    const fecParams = enable ? 
      {
    
     type: 'reed-solomon', ratio: 0.2 } : 
      {
    
     type: 'none' };
    videoEncoder.setFEC(fecParams);
  }
}

四、设备虚拟化技术

4.1 虚拟设备映射

// 智能手表虚拟手机摄像头示例
class VirtualCamera {
    
    
  private physicalDevice: CameraDevice;
  private virtualDevice: VirtualDevice;

  constructor() {
    
    
    this.physicalDevice = sensor.getCamera(CameraType.BACK);
    this.virtualDevice = deviceVirtualization.createVirtualDevice(
      DeviceType.CAMERA,
      this.getCapabilities()
    );
  }

  private getCapabilities() {
    
    
    return {
    
    
      resolution: '720p',
      frameRate: 30,
      formats: ['NV21', 'YUV420']
    };
  }

  startStreaming() {
    
    
    this.physicalDevice.on('frame', (frame) => {
    
    
      const processedFrame = this.processFrame(frame);
      this.virtualDevice.pushFrame(processedFrame);
    });
  }

  private processFrame(frame: CameraFrame) {
    
    
    // 添加水印等处理
    return frame.resize(1280, 720)
                .convertFormat('NV21');
  }
}