websocket 給人的印象就是使用非常簡(jiǎn)單，比原生Socket像 Netty 等簡(jiǎn)單很多。無(wú)論服務(wù)端還是客戶端都很簡(jiǎn)單

OkHttp3 也是支持WebSocket的，因?yàn)?android 網(wǎng)絡(luò)請(qǐng)求基本都用OkHttp3，所以沒(méi)必要引入其他的框架了。

import android.app.Service;
import android.content.Intent;
import android.os.Binder;
import android.os.Handler;
import android.os.IBinder;
import android.util.Log;

import androidx.annotation.Nullable;

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import okhttp3.WebSocket;
import okhttp3.WebSocketListener;

public class WebSocketService extends Service {
    private static final String TAG = "websocket";
    private static final String WS = "ws://121.40.165.18:8800";

    private WebSocket webSocket;
    private WebSocketCallback webSocketCallback;
    private int reconnectTimeout = 5000;
    private boolean connected = false;

    private Handler handler = new Handler();

    class LocalBinder extends Binder {
        WebSocketService getService() {
            return WebSocketService.this;
        }
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return new LocalBinder();
    }

    @Override
    public void onCreate() {
        super.onCreate();
        webSocket = connect();
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        if (webSocket != null) {
            close();
        }
    }

    private WebSocket connect() {
        Log.d(TAG, "connect " + WS);
        OkHttpClient client = new OkHttpClient.Builder().build();
        Request request = new Request.Builder().url(WS).build();
        return client.newWebSocket(request, new WebSocketHandler());
    }

    public void send(String text) {
        Log.d(TAG, "send " + text);
        if (webSocket != null) {
            webSocket.send(text);
        }
    }

    public void close() {
        if (webSocket != null) {
            boolean shutDownFlag = webSocket.close(1000, "manual close");
            Log.d(TAG, "shutDownFlag " + shutDownFlag);
            webSocket = null;
        }
    }

    private void reconnect() {
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                Log.d(TAG, "reconnect...");
                if (!connected) {
                    connect();
                    handler.postDelayed(this, reconnectTimeout);
                }
            }
        }, reconnectTimeout);
    }

    private class WebSocketHandler extends WebSocketListener {

        @Override
        public void onOpen(WebSocket webSocket, Response response) {
            Log.d(TAG, "onOpen");
            if (webSocketCallback != null) {
                webSocketCallback.onOpen();
            }
            connected = true;
        }

        @Override
        public void onMessage(WebSocket webSocket, String text) {
            Log.d(TAG, "onMessage " + text);
            if (webSocketCallback != null) {
                webSocketCallback.onMessage(text);
            }
        }

        @Override
        public void onClosed(WebSocket webSocket, int code, String reason) {
            Log.d(TAG, "onClosed");
            if (webSocketCallback != null) {
                webSocketCallback.onClosed();
            }
            connected = false;
            reconnect();
        }

        /**
         * Invoked when a web socket has been closed due to an error reading from or writing to the
         * network. Both outgoing and incoming messages may have been lost. No further calls to this
         * listener will be made.
         */
        @Override
        public void onFailure(WebSocket webSocket, Throwable t, Response response) {
            Log.d(TAG, "onFailure " + t.getMessage());
            connected = false;
            reconnect();
        }
    }

    /**
     * 只暴露需要的回調(diào)給頁(yè)面，onFailure 你給了頁(yè)面，頁(yè)面也無(wú)能為力不知怎么處理
     */
    public interface WebSocketCallback {
        void onMessage(String text);

        void onOpen();

        void onClosed();
    }

    public void setWebSocketCallback(WebSocketCallback webSocketCallback) {
        this.webSocketCallback = webSocketCallback;
    }
}

前端使用時(shí) bind 上Service就行了

public class MainActivity extends AppCompatActivity {
    WebSocketService webSocketService;
    TextView tvMessage;
    EditText etValue;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        bindService(new Intent(this, WebSocketService.class), serviceConnection, BIND_AUTO_CREATE);

        btnClose.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (webSocketService != null) {
                    webSocketService.close();
                }
            }
        });
        btnSend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (webSocketService != null) {
                    webSocketService.send(etValue.getText().toString().trim());
                }
            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unbindService(serviceConnection);
    }

    private ServiceConnection serviceConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            webSocketService = ((WebSocketService.LocalBinder) service).getService();
            webSocketService.setWebSocketCallback(webSocketCallback);
        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            webSocketService = null;
        }
    };

    private WebSocketService.WebSocketCallback webSocketCallback = new WebSocketService.WebSocketCallback() {
        @Override
        public void onMessage(final String text) {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    tvMessage.setText(text);
                }
            });
        }

        @Override
        public void onOpen() {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    tvMessage.setText("onOpen");
                }
            });
        }

        @Override
        public void onClosed() {
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    tvMessage.setText("onClosed");
                }
            });
        }
    };
}

demo: https://github.com/lesliebeijing/okhttp-websocket/tree/master