Android设备通过USB线连接PC进行Socket通信

Android设备分别作为客户端和服务端与PC通讯

背景简介
核心原理
整体思路
代码讲解
- 1.创建广播监听类ConnectStateReceiver
- 2.建立Socket连接
- 3.Socket连接成功，数据交互
- 4.断开连接，释放资源
彩蛋部分
- 1.FileTransferUtil.java
- 1.SendRequestUtil.java
完整Demo下载：

背景简介

这是一项比较老旧的技术了，不过在一些特定的场合（例如：无网络），进行传输数据，使用这项技术还是很方便的。网上有好很多类似的文章，个人觉得都不是特别完整，正好公司最近有涉及这方面的功能需求，借此机会整理Android分别作为客户端和服务端的实现。

核心原理

其实Socket通信，最根本的就是，Socket客户端和Socket服务端通过输入流和输出流进行数据传输。

整体思路

1.通过广播，来监听USB状态及Socket状态。
2.建立Socket连接。
3.获取Socket对象中的输入流或输出流，实现数据的接收或发送。
4.释放资源，关闭连接。

代码讲解

使用Rxjava和线程池来进行异步处理，发挥Service的优势增加稳定性。虽然是个小的功能，不过我也进行了多层封装，是代码更加健壮，灵活。

1.创建广播监听类ConnectStateReceiver

根据不同场景，分别进行说明

//服务端在监听
private static final String ACTION_SERVER_LISTENING = "SocketServerListening";
//Socket连接成功
private static final String ACTION_CONNECT_SUCCESS = "SocketConnectSuccess";
//Socket连接失败
private static final String ACTION_CONNECT_FAIL = "SocketConnectFail";
//USB线连接状态
private static final String ACTION_USB_STATE = "android.hardware.usb.action.USB_STATE";

场景一，Android作为客户端，PC作为服务端：（要求Android设备与PC所处同一局域网内）
1.ACTION_USB_STATE ：USB连接状态，系统自行发送。
2.ACTION_SERVER_LISTENING ：PC的Socket服务端正在监听，PC发送。
3.ACTION_CONNECT_SUCCESS ：Socket连接成功，PC发送。
4.ACTION_CONNECT_FAIL ：Socket连接失败，PC发送。

场景二，Android作为服务端，PC作为客户端：
1.ACTION_USB_STATE ：USB连接状态，系统自行发送。
2.ACTION_CONNECT_SUCCESS ：Socket连接成功，Android发送。
3.ACTION_CONNECT_FAIL ：Socket连接失败，Android发送。
如何处理接收到的通知：

        String action = intent.getAction();if (TextUtils.equals(action, ACTION_SERVER_LISTENING)) {ToastUtil.showToast(context, "服务端开始监听");LogUtil.e("服务端开始监听");//连接服务端SocketManager.getInstance().connectServer(context);} else if (TextUtils.equals(action, ACTION_CONNECT_SUCCESS)) {ToastUtil.showToast(context, "Socket连接成功");LogUtil.e("Socket连接成功");//1.初始化发送请求工具类SendRequestUtil.getInstance().init(SocketManager.getInstance().getDataOutputStream());//2.启动Service，接收消息context.startService(new Intent(context, DataService.class));} else if (TextUtils.equals(action, ACTION_CONNECT_FAIL)) {ToastUtil.showToast(context, "Socket连接失败");LogUtil.e("Socket连接失败");} else if (TextUtils.equals(action, ACTION_USB_STATE)) {boolean connectedState = intent.getBooleanExtra("connected", false);if (connectedState) {ToastUtil.showToast(context, "USB已连接，开始监听客户端");LogUtil.e("USB已连接，开始监听客户端");//开始监听SocketManager.getInstance().acceptClient(context);} else {ToastUtil.showToast(context, "USB断开连接");LogUtil.e("USB断开连接");//1.关闭Service，停止接收消息context.stopService(new Intent(context, DataService.class));//2.释放socketSocketManager.getInstance().close();}}

以上代码结合了两种场景，可以根据自己的需求，对代码进行适当删减。

2.建立Socket连接

根据不同场景，分别进行说明

场景一，Android作为客户端，PC作为服务端：（要求Android设备与PC所处同一局域网内）
收到PC端发来的“Socket服务端正在监听”通知（即ACTION_SERVER_LISTENING）后，进行连接操作：

    public void connectServer(final Context context) {mConnectDisposable = Observable.create(new ObservableOnSubscribe<Boolean>() {@Overridepublic void subscribe(ObservableEmitter<Boolean> emitter) throws Exception {Socket socket = connect();if (socket != null) {emitter.onNext(true);} else {emitter.onNext(false);}emitter.onComplete();}}).subscribeOn(Schedulers.newThread()).observeOn(AndroidSchedulers.mainThread()).subscribe(new Consumer<Boolean>() {@Overridepublic void accept(Boolean aBoolean) throws Exception {if (aBoolean) {ToastUtil.showToast(context, "连接服务端成功");mState = STATE_CONNECT_SUCCESSED;} else {ToastUtil.showToast(context, "连接服务端失败");mState = STATE_CONNECT_FAILED;//弹出Dialog，提示重新连接}}});}private Socket connect() {Socket socket = null;try {socket = new Socket(AppConfig.SERVER_ADDRESS, AppConfig.SERVER_PORT);} catch (IOException e) {e.printStackTrace();}if (socket != null) {mSocket = socket;try {mDataInputStream = new DataInputStream(mSocket.getInputStream());mDataOutputStream = new DataOutputStream(mSocket.getOutputStream());} catch (IOException e) {e.printStackTrace();}}return socket;}

场景二，Android作为服务端，PC作为客户端：
当收到系统发送的“USB已连接状态”通知(即ACTION_USB_STATE)，后进行Socket监听，等待PC接入：

    public void acceptClient(final Context context) {if(mState != STATE_LISTEN){mState = STATE_LISTEN;mAcceptDisposable = Observable.create(new ObservableOnSubscribe<Boolean>() {@Overridepublic void subscribe(ObservableEmitter<Boolean> emitter) throws Exception {Socket socket = accept();if (socket != null) {emitter.onNext(true);} else {emitter.onNext(false);}emitter.onComplete();}}).subscribeOn(Schedulers.newThread()).observeOn(AndroidSchedulers.mainThread()).subscribe(new Consumer<Boolean>() {@Overridepublic void accept(Boolean aBoolean) throws Exception {if (aBoolean) {ToastUtil.showToast(context, "接入客户端成功");mState = STATE_CONNECT_SUCCESSED;context.sendBroadcast(new Intent(ConnectStateReceiver.ACTION_CONNECT_SUCCESS));} else {ToastUtil.showToast(context, "接入客户端失败");mState = STATE_CONNECT_FAILED;context.sendBroadcast(new Intent(ConnectStateReceiver.ACTION_CONNECT_FAIL));}}});}}private Socket accept() {Socket socket = null;try {if(mServerSocket == null){mServerSocket = new ServerSocket(AppConfig.LOCAL_PORT);}socket = mServerSocket.accept();} catch (IOException e) {e.printStackTrace();}if (socket != null) {mSocket = socket;try {mDataInputStream = new DataInputStream(mSocket.getInputStream());mDataOutputStream = new DataOutputStream(mSocket.getOutputStream());mServerSocket.close();} catch (IOException e) {e.printStackTrace();}}return socket;}

3.Socket连接成功，数据交互

Socket成功建立连接，收到“Socket连接成功”通知（即ACTION_CONNECT_SUCCESS），我们就可以通过操作Socket提供的输入流和输出流进行数据交互。
Socket为双向通信，既可以接收数据，也可以发送数据。
接收数据
原理：读取Socket中的输入流，如果需要下载文件，则配合本地的输出流，就可以进行消息或文件的接收。
在后台启动一个Service，用于接收数据，直到USB断开连接。

context.startService(new Intent(context, DataService.class));

以下为Service代码以及接收数据线程的代码（FileTransferUtil是封装的工具类，用于文件的操作）：

public class DataService extends Service {private ExecutorService mExecutorService;@Overridepublic IBinder onBind(Intent intent) {return null;}@Overridepublic void onCreate() {super.onCreate();mExecutorService = Executors.newCachedThreadPool();}@Overridepublic int onStartCommand(Intent intent, int flags, int startId) {ReceiveRunnable receiveRunnable = new ReceiveRunnable(SocketManager.getInstance().getDataInputStream());mExecutorService.execute(receiveRunnable);return START_NOT_STICKY;}@Overridepublic void onDestroy() {super.onDestroy();mExecutorService.shutdown();}
}public class ReceiveRunnable implements Runnable {private DataInputStream mDataInputStream;public ReceiveRunnable(DataInputStream dis) {mDataInputStream = dis;}@Overridepublic void run() {try {while (true) {String jsonRaw = mDataInputStream.readUTF();DataEvent dataEvent = new DataEvent("testJSON");dataEvent.setTestJSON(jsonRaw);EventManager.post(dataEvent);FileTransferUtil.getInstance().downloadFile(mDataInputStream, fileLength);}} catch (IOException e) {e.printStackTrace();}}
}

发送数据
原理：操作Socket中的输出流，如果需要上传文件，则配合本地的输入流，就可以进行消息或文件的发送。
初始化SendRequestUtil工具类

SendRequestUtil.getInstance().init(SocketManager.getInstance().getDataOutputStream());

（SendRequestUtil是封装的工具类，用于发送消息及文件操作，可随时在点击事件里面进行调用）
以下为SendRequestUtil中的核心代码：

public Disposable post(final String jsonString, final File localFile) {return Observable.create(new ObservableOnSubscribe<Boolean>() {@Overridepublic void subscribe(ObservableEmitter<Boolean> emitter) throws Exception {if (localFile == null) {emitter.onNext(sendInfor(jsonString));} else {emitter.onNext(sendInforAndFile(jsonString, localFile));}emitter.onComplete();}}).subscribeOn(Schedulers.newThread()).observeOn(AndroidSchedulers.mainThread()).subscribe(new Consumer<Boolean>() {@Overridepublic void accept(Boolean aBoolean) throws Exception {if(mRequestListener ==  null){return;}if(aBoolean){mRequestListener.onRequestSuccessed();}else{mRequestListener.onRequestFailed();}}});}private boolean sendInfor(String json) {try {mDataOutputStream.writeUTF(json);mDataOutputStream.flush();} catch (IOException e) {e.printStackTrace();try {mDataOutputStream.flush();} catch (IOException e1) {e1.printStackTrace();}return false;}return true;}private boolean sendInforAndFile(String json, File file) {boolean result = false;try {mDataOutputStream.writeUTF(json);result = FileTransferUtil.getInstance().uploadFile(mDataOutputStream, file);} catch (IOException e) {e.printStackTrace();}return result;}

4.断开连接，释放资源

在我们数据交互结束后，一定要记得释放资源。
通过监听USB的连接状态，可以在USB线断开连接的时候，收到“USB连接状态”通知（即ACTION_USB_STATE），进行资源的释放。
1.停止Service，不再接收数据。

context.stopService(new Intent(context, DataService.class));

2.释放socket，关闭文件流

SocketManager.getInstance().close();

看一下close()方法中的代码：

  public void close() {if (mSocket != null) {mState = STATE_NONE;try {mDataInputStream.close();mDataOutputStream.close();mSocket.close();mSocket = null;} catch (IOException e) {e.printStackTrace();}}}

彩蛋部分

1.FileTransferUtil.java

public class FileTransferUtil {private static volatile FileTransferUtil mInstance = null;private Timer mTimer;private TimerTask mTimerTask = null;private String mProgress = "";private FileTransferUtil() {mTimer = new Timer();}public static FileTransferUtil getInstance() {if (mInstance == null) {synchronized (FileTransferUtil.class) {if (mInstance == null) {mInstance = new FileTransferUtil();}}}return mInstance;}public void downloadFile(DataInputStream dataInputStream, long fileLength) {FileOutputStream fos = null;try {fos = new FileOutputStream(AppConfig.SAVE_PATH + AppConfig.DB_FILE_NAME);byte[] b = new byte[4 * 1024];int length;long writeLength = 0L;while ((length = dataInputStream.read(b)) != -1) {fos.write(b, 0, length);writeLength += length;int progress = (int) (((float) writeLength / (float) fileLength) * 100);if (writeLength >= fileLength) {transferCompleted();break;}updateProgress(progress + "%");}} catch (IOException ioe) {ioe.printStackTrace();transferFailed();} finally {try {if (fos != null) {fos.close();}} catch (IOException e) {e.printStackTrace();}}}public boolean uploadFile(DataOutputStream dataOutputStream, File file) {FileInputStream fis = null;try {long fileLength = file.length();fis = new FileInputStream(file);int length;long readLength = 0L;byte[] b = new byte[4 * 1024];while ((length = fis.read(b)) != -1) {dataOutputStream.write(b, 0, length);readLength += (long) length;int progress = (int) (((float) readLength / (float) fileLength) * 100);if (readLength >= fileLength) {transferCompleted();break;}updateProgress(progress + "%");}return true;} catch (IOException ioe) {ioe.printStackTrace();transferFailed();return false;} finally {try {if (fis != null) {fis.close();}dataOutputStream.flush();} catch (IOException e) {e.printStackTrace();}}}private void updateProgress(String progress) {mProgress = progress;if (mTimerTask == null) {mTimerTask = new TimerTask() {@Overridepublic void run() {DataEvent dataEvent = new DataEvent(FileConstant.FILE_PROGRESS);dataEvent.setProgress(mProgress);EventManager.post(dataEvent);}};mTimer.schedule(mTimerTask, 1000);}}private void transferCompleted() {mTimer.cancel();mTimerTask = null;DataEvent dataEvent = new DataEvent(FileConstant.FILE_TRANSFER_COMPLETE);dataEvent.setProgress("100%");EventManager.post(dataEvent);}private void transferFailed() {mTimer.cancel();mTimerTask = null;DataEvent dataEvent = new DataEvent(FileConstant.FILE_TRANSFER_FAILED);EventManager.post(dataEvent);}
}

1.SendRequestUtil.java

public class SendRequestUtil {private DataOutputStream mDataOutputStream;private SendRequestUtil() {}private static class Holder {private static final SendRequestUtil INSTANCE = new SendRequestUtil();}public static SendRequestUtil getInstance() {return Holder.INSTANCE;}public void init(DataOutputStream dos) {mDataOutputStream = dos;}public Disposable post(final String jsonString, final File localFile) {return Observable.create(new ObservableOnSubscribe<Boolean>() {@Overridepublic void subscribe(ObservableEmitter<Boolean> emitter) throws Exception {if (localFile == null) {emitter.onNext(sendInfor(jsonString));} else {emitter.onNext(sendInforAndFile(jsonString, localFile));}emitter.onComplete();}}).subscribeOn(Schedulers.newThread()).observeOn(AndroidSchedulers.mainThread()).subscribe(new Consumer<Boolean>() {@Overridepublic void accept(Boolean aBoolean) throws Exception {if(mRequestListener ==  null){return;}if(aBoolean){mRequestListener.onRequestSuccessed();}else{mRequestListener.onRequestFailed();}}});}private boolean sendInfor(String json) {try {mDataOutputStream.writeUTF(json);mDataOutputStream.flush();} catch (IOException e) {e.printStackTrace();try {mDataOutputStream.flush();} catch (IOException e1) {e1.printStackTrace();}return false;}return true;}private boolean sendInforAndFile(String json, File file) {boolean result = false;try {mDataOutputStream.writeUTF(json);result = FileTransferUtil.getInstance().uploadFile(mDataOutputStream, file);} catch (IOException e) {e.printStackTrace();}return result;}private OnRequestListener mRequestListener;public void registerRequestListener(OnRequestListener listener){this.mRequestListener = listener;}public void unregisterRequestListener(){this.mRequestListener = null;}public interface OnRequestListener{void onRequestSuccessed();void onRequestFailed();}
}

完整Demo下载：

USBSocketClient.
说明： 我的开发环境有点旧，是Android Studio3.2，下载源码如果出现build失败，请更换build.gradle中依赖包的版本，或直接屏蔽掉，不影响功能。

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