Implement WebSocket module for Android. Fixes #2837

Summary: The JavaScript code for Android is same as the iOS counterpart, I just added few new lines and used arrow functions instead of binding `this`.
Closes https://github.com/facebook/react-native/pull/2839

Reviewed By: @​svcscm, @vjeux

Differential Revision: D2498703

Pulled By: @mkonicek

fb-gh-sync-id: 3fe958dd5af0efba00df07515f8e33b5d87eb05b

Libraries/WebSocket/WebSocket.js

@@ -0,0 +1,124 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @providesModule WebSocket
+ */
+'use strict';
+
+var RCTDeviceEventEmitter = require('RCTDeviceEventEmitter');
+var RCTWebSocketModule = require('NativeModules').WebSocketModule;
+
+var Platform = require('Platform');
+var WebSocketBase = require('WebSocketBase');
+var WebSocketEvent = require('WebSocketEvent');
+
+var WebSocketId = 0;
+var CLOSE_NORMAL = 1000;
+
+/**
+ * Browser-compatible WebSockets implementation.
+ *
+ * See https://developer.mozilla.org/en-US/docs/Web/API/WebSocket
+ */
+class WebSocket extends WebSocketBase {
+  _socketId: number;
+  _subs: any;
+
+  connectToSocketImpl(url: string): void {
+    this._socketId = WebSocketId++;
+
+    RCTWebSocketModule.connect(url, this._socketId);
+
+    this._registerEvents(this._socketId);
+  }
+
+  closeConnectionImpl(code?: number, reason?: string): void {
+    this._closeWebSocket(this._socketId, code, reason);
+  }
+
+  cancelConnectionImpl(): void {
+    this._closeWebSocket(this._socketId);
+  }
+
+  sendStringImpl(message: string): void {
+    RCTWebSocketModule.send(message, this._socketId);
+  }
+
+  sendArrayBufferImpl(): void {
+    // TODO
+    console.warn('Sending ArrayBuffers is not yet supported');
+  }
+
+  _closeWebSocket(id: number, code?: number, reason?: string): void {
+    if (Platform.OS === 'android') {
+      /*
+       * See https://developer.mozilla.org/en-US/docs/Web/API/CloseEvent
+       */
+      var statusCode = typeof code === 'number' ? code : CLOSE_NORMAL;
+      var closeReason = typeof reason === 'string' ? reason : '';
+      RCTWebSocketModule.close(statusCode, closeReason, id);
+    } else {
+      RCTWebSocketModule.close(id);
+    }
+  }
+
+  _unregisterEvents(): void {
+    this._subs.forEach(e => e.remove());
+    this._subs = [];
+  }
+
+  _registerEvents(id: number): void {
+    this._subs = [
+      RCTDeviceEventEmitter.addListener('websocketMessage', ev => {
+        if (ev.id !== id) {
+          return;
+        }
+        var event = new WebSocketEvent('message', {
+          data: ev.data
+        });
+        this.onmessage && this.onmessage(event);
+        this.dispatchEvent(event);
+      }),
+      RCTDeviceEventEmitter.addListener('websocketOpen', ev => {
+        if (ev.id !== id) {
+          return;
+        }
+        this.readyState = this.OPEN;
+        var event = new WebSocketEvent('open');
+        this.onopen && this.onopen(event);
+        this.dispatchEvent(event);
+      }),
+      RCTDeviceEventEmitter.addListener('websocketClosed', ev => {
+        if (ev.id !== id) {
+          return;
+        }
+        this.readyState = this.CLOSED;
+        var event = new WebSocketEvent('close');
+        event.code = ev.code;
+        event.reason = ev.reason;
+        this.onclose && this.onclose(event);
+        this.dispatchEvent(event);
+        this._unregisterEvents();
+        this._closeWebSocket(id);
+      }),
+      RCTDeviceEventEmitter.addListener('websocketFailed', ev => {
+        if (ev.id !== id) {
+          return;
+        }
+        var event = new WebSocketEvent('error');
+        event.message = ev.message;
+        this.onerror && this.onerror(event);
+        this.dispatchEvent(event);
+        this._unregisterEvents();
+        this._closeWebSocket(id);
+      })
+    ];
+  }
+}
+
+module.exports = WebSocket;