在Grpc-Android Java中使用双向流时如何检测（物理）断开

Question

我有使用双向流的GRPC使用异步存根的概念。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    btnOnline = (Button) findViewById(R.id.btnOnline);
    btnOffline = (Button) findViewById(R.id.btnOffline);
    btnAcceptRide = (Button) findViewById(R.id.btnAcceptRide);
    btnCancelRide = (Button) findViewById(R.id.btnCancelRide);
    txtCode = (EditText) findViewById(R.id.txtCode);
    txtReply = (TextView) findViewById(R.id.txtReply);
    ClientConnState = 0;
    btnOnline.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            new GrpcTask().execute();

        }
    });
  private class GrpcTask extends AsyncTask<Void, Void, String> {
    private String mHost;
    private String mMessage;
    private int mPort;
    private ManagedChannel mChannel;

    @Override
    protected void onPreExecute() {
        mHost = "localhost";
        mPort = 8080;
        mChannel = ManagedChannelBuilder.forAddress("192.168.0.102", 50049)
                .usePlaintext(true)
                .build();
        blockingStub = bidirectionalserviceGrpc.newBlockingStub(mChannel);
        asyncStub = bidirectionalserviceGrpc.newStub(mChannel);
    }

    @Override
    protected String doInBackground(Void... nothing) {
        try {
            final CountDownLatch countDownLatch = new CountDownLatch(1);
            requestStreamObserver = asyncStub.requestRide(new StreamObserver<Bidirectional.RideReply>() {
                @Override
                public void onNext(Bidirectional.RideReply value) {
                    if (countDownLatch.getCount() > 0) {
                        countDownLatch.countDown();
                    }                     
                }

                @Override
                public void onError(Throwable t) {
                    countDownLatch.countDown();
                }

                @Override
                public void onCompleted() {
                    countDownLatch.countDown();
                }
            });
            Bidirectional.RideRequest rideRequest = Bidirectional.RideRequest.newBuilder()
                    .setRequestid(1)
                    .setDrivercode(txtCode.getText().toString())
                    .build();
            requestStreamObserver.onNext(rideRequest);
            if (!countDownLatch.await(15, TimeUnit.SECONDS)) {
                throw new RuntimeException(
                        "Could not finish rpc within 1 minute, the server is likely down");
            }
            return "completed";
        } catch (Exception e) {
            StringWriter sw = new StringWriter();
            PrintWriter pw = new PrintWriter(sw);
            e.printStackTrace(pw);
            pw.flush();
            return "Failed... : " + System.lineSeparator() + sw;
        }
    }

    @Override
    protected void onPostExecute(String result) {
        Log.e(logger.getName(), result);
    }
}
  final Handler handler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        // Write Logic here
        super.handleMessage(msg);
    }
};

Answer 1

TCP可能不会发现连接中断，这取决于服务器如何宕机和客户端正在做什么。您应该在ManagedChannelBuilder上启用KeepAliveTime()。Javadoc应该能让您入门，如果您感兴趣的话，8-client-side-keepalive.md有更多的信息。

您可能还希望启用idletimeout()。