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The Netty project is an effort to provide an asynchronous event-driven network application framework and tools for rapid development of maintainable high performance and high scalability protocol servers and clients. In other words, Netty is a NIO client server framework which enables quick and easy development of network applications such as protocol servers and clients. It greatly simplifies and streamlines network programming such as TCP and UDP socket server.

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/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package org.jboss.netty.handler.codec.http.websocketx;

import static org.jboss.netty.handler.codec.http.HttpVersion.HTTP_1_1;

import org.jboss.netty.buffer.ChannelBuffers;
import org.jboss.netty.channel.ChannelFutureListener;
import org.jboss.netty.channel.ChannelHandler;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.channel.ChannelPipeline;
import org.jboss.netty.channel.ExceptionEvent;
import org.jboss.netty.channel.LifeCycleAwareChannelHandler;
import org.jboss.netty.channel.MessageEvent;
import org.jboss.netty.channel.SimpleChannelHandler;
import org.jboss.netty.channel.SimpleChannelUpstreamHandler;
import org.jboss.netty.handler.codec.http.DefaultHttpResponse;
import org.jboss.netty.handler.codec.http.HttpResponseStatus;

/**
 * Handles WebSocket control frames (Close, Ping, Pong) and data frames (Text and Binary) are passed
 * to the next handler in the pipeline.
 */
public class WebSocketServerProtocolHandler extends SimpleChannelUpstreamHandler implements
    LifeCycleAwareChannelHandler {

    private final String websocketPath;
    private final String subprotocols;
    private final boolean allowExtensions;

    public WebSocketServerProtocolHandler(String websocketPath) {
        this(websocketPath, null, false);
    }

    public WebSocketServerProtocolHandler(String websocketPath, String subprotocols) {
        this(websocketPath, subprotocols, false);
    }

    public WebSocketServerProtocolHandler(String websocketPath, String subprotocols, boolean allowExtensions) {
        this.websocketPath = websocketPath;
        this.subprotocols = subprotocols;
        this.allowExtensions = allowExtensions;
    }

    public void afterAdd(ChannelHandlerContext ctx) throws Exception {
        ChannelPipeline cp = ctx.getPipeline();
        if (cp.get(WebSocketServerProtocolHandshakeHandler.class) == null) {
            // Add the WebSocketHandshakeHandler before this one.
            ctx.getPipeline().addBefore(ctx.getName(), WebSocketServerProtocolHandshakeHandler.class.getName(),
                    new WebSocketServerProtocolHandshakeHandler(websocketPath, subprotocols, allowExtensions));
        }
    }

    @Override
    public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
        if (e.getMessage() instanceof WebSocketFrame) {
            WebSocketFrame frame = (WebSocketFrame) e.getMessage();
            if (frame instanceof CloseWebSocketFrame) {
                WebSocketServerHandshaker handshaker = getHandshaker(ctx);
                handshaker.close(ctx.getChannel(), (CloseWebSocketFrame) frame);
                return;
            } else if (frame instanceof PingWebSocketFrame) {
                ctx.getChannel().write(new PongWebSocketFrame(frame.getBinaryData()));
                return;
            }
        }
        ctx.sendUpstream(e);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, ExceptionEvent e) throws Exception {
        if (e.getCause() instanceof WebSocketHandshakeException) {
            DefaultHttpResponse response = new DefaultHttpResponse(HTTP_1_1, HttpResponseStatus.BAD_REQUEST);
            response.setContent(ChannelBuffers.wrappedBuffer(e.getCause().getMessage().getBytes()));
            ctx.getChannel().write(response).addListener(ChannelFutureListener.CLOSE);
        } else {
            ctx.getChannel().close();
        }
    }

    static WebSocketServerHandshaker getHandshaker(ChannelHandlerContext ctx) {
        return (WebSocketServerHandshaker) ctx.getAttachment();
    }

    static void setHandshaker(ChannelHandlerContext ctx, WebSocketServerHandshaker handshaker) {
        ctx.setAttachment(handshaker);
    }

    static ChannelHandler forbiddenHttpRequestResponder() {
        return new SimpleChannelHandler() {
            @Override
            public void messageReceived(ChannelHandlerContext ctx, MessageEvent e) throws Exception {
                if (!(e.getMessage() instanceof WebSocketFrame)) {
                    DefaultHttpResponse response = new DefaultHttpResponse(HTTP_1_1, HttpResponseStatus.FORBIDDEN);
                    ctx.getChannel().write(response);
                } else {
                    ctx.sendUpstream(e);
                }
            }
        };
    }

    public void beforeAdd(ChannelHandlerContext ctx) throws Exception {
    }

    public void beforeRemove(ChannelHandlerContext ctx) throws Exception {
    }

    public void afterRemove(ChannelHandlerContext ctx) throws Exception {
    }
}