没有浏览器的Java Websocket客户端

Question

我正在开发一个需要用户之间进行实时交互的项目。 我希望有一个HTML5 Web客户端（足够简单）和一个本地客户端（最好是Java），它们都可以连接到服务器。 我做了一些研究，并没有找到一个结论性的答案，本地客户端是否可以在没有浏览器的情况下连接到服务器。

问题：有没有办法在没有浏览的情况下从本地Java客户端连接到websocket服务器？ 我已经看到其他语言中的一些浏览器包装器可能使这成为可能。 如果没有，我愿意接受建议。

谢谢。

Answer 1

您当然可以在浏览器沙箱之外的Java中使用来自桌面应用程序的WebSockets。 这背后的想法是您可以创建创建TCP连接的胖客户端，因此他们当然应该能够在这些TCP连接之上创建WebSocket连接。

这样做的最新和最好的API之一是由Kaazing编写的，它认为WebSocket就像一个套接字，可以使用简单的“ws：//”URI创建。

在Kaazing Gateway 5.0 Java WebSocket文档站点上详细讨论了API。 您可以在这里从Kaazing下载普通网关

创建一个websocket：

    import com.kaazing.net.ws.WebSocket;
    import com.kaazing.net.ws.WebSocketFactory;

    wsFactory = WebSocketFactory.createWebSocketFactory();
    ws = wsFactory.createWebSocket(URI.create("ws://example.com:8001/path"));
    ws.connect(); // This will block or throw an exception if failed.

要发送消息，请添加WebSocketMessageWriter对象：

    WebSocketMessageWriter writer = ws.getMessageWriter();
    String text = "Hello WebSocket!";
    writer.writeText(text);   // Send text message

要接收或使用消息，请添加WebSocket和WebSocketMessageReader对象：

    wsFactory = WebSocketFactory.createWebSocketFactory();
    ws = wsFactory.createWebSocket(URI.create("ws://example.com:8001/path"));
    ws.connect(); // This will block or throw an exception if failed.

    WebSocketMessageReader reader = ws.getMessageReader();
    WebSocketMessageType type = null; // Block till a message arrives
      // Loop till the connection goes away
      while ((type =  reader.next()) != WebSocketMessageType.EOS) {
        switch (type) { // Handle both text and binary messages
          case TEXT:
            CharSequence text = reader.getText();
            log("RECEIVED TEXT MESSAGE: " + text.toString());
            break;
          case BINARY:
            ByteBuffer buffer = reader.getBinary();
            log("RECEIVED BINARY MESSAGE: " + getHexDump(buffer));
            break;
        }
    }

（完全披露：我曾在Kaazing Corporation担任服务器工程师。）

Answer 2

您还可以考虑使用JSR 356 - Java API for WebSocket 。 它是Java EE 7的一部分，但客户端可以从普通的Java SE运行而不会出现任何问题。 现在有多种实现可用，所有这些实现都可以使用：

程序化API：

    final WebSocketContainer webSocketContainer = ContainerProvider.getWebSocketContainer();

    Session session = webSocketContainer.connectToServer(new Endpoint() {
        @Override
        public void onOpen(Session session, EndpointConfig config) {
            // session.addMessageHandler( ... );
        }
    }, URI.create("ws://some.uri"));

带注释的API：

public static void main(String[] args) throws IOException, DeploymentException {
    final WebSocketContainer webSocketContainer = ContainerProvider.getWebSocketContainer();
    webSocketContainer.connectToServer(MyEndpoint.class, URI.create("ws://some.uri"));
}

@ClientEndpoint
public static class MyEndpoint {

    // text
    @OnMessage
    void onMessage(Session session, String message) {
        // ...
    }

    // binary
    @OnMessage
    void onMessage(Session session, ByteBuffer message) {
        // ...
    }

    // @OnClose, @OnOpen, @OnError
}

请参阅链接页面了解更多详情（完整规格）。

这里有各种实现，基本上每个Java容器都有一个。 我正在开发Glassfish / WebLogic实现，它叫做Tyrus ，可以随意尝试（我们提供易于使用的所有功能，请参见http：//search.maven.org / ... ）。

Answer 3

Vert.x有一个java websocket客户端：

VertxFactory.newVertx()
    .createHttpClient()
    .setHost("localhost")
    .setPort(8080)
    .connectWebsocket("/ws", new Handler<WebSocket>() {

            @Override
            public void handle(final WebSocket webSocket) {

                // Listen
                webSocket.dataHandler(new Handler<Buffer>() {
                    @Override
                    public void handle(Buffer buff) {
                        log.info("Received {}", buff.toString());
                    }
                });

                // Publish
                webSocket.writeTextFrame("Heya");
            }
        });

Answer 4

Netty是这项任务的不错选择，它是一个高性能的网络应用程序框架，它优雅地支持SSL，这里是来自netty github的netty websocket客户端示例 ：

public final class WebSocketClient {

static final String URL = System.getProperty("url", "ws://127.0.0.1:8080/websocket");

public static void main(String[] args) throws Exception {
    URI uri = new URI(URL);
    String scheme = uri.getScheme() == null? "ws" : uri.getScheme();
    final String host = uri.getHost() == null? "127.0.0.1" : uri.getHost();
    final int port;
    if (uri.getPort() == -1) {
        if ("ws".equalsIgnoreCase(scheme)) {
            port = 80;
        } else if ("wss".equalsIgnoreCase(scheme)) {
            port = 443;
        } else {
            port = -1;
        }
    } else {
        port = uri.getPort();
    }

    if (!"ws".equalsIgnoreCase(scheme) && !"wss".equalsIgnoreCase(scheme)) {
        System.err.println("Only WS(S) is supported.");
        return;
    }

    final boolean ssl = "wss".equalsIgnoreCase(scheme);
    final SslContext sslCtx;
    if (ssl) {
        sslCtx = SslContextBuilder.forClient()
            .trustManager(InsecureTrustManagerFactory.INSTANCE).build();
    } else {
        sslCtx = null;
    }

    EventLoopGroup group = new NioEventLoopGroup();
    try {
        // Connect with V13 (RFC 6455 aka HyBi-17). You can change it to V08 or V00.
        // If you change it to V00, ping is not supported and remember to change
        // HttpResponseDecoder to WebSocketHttpResponseDecoder in the pipeline.
        final WebSocketClientHandler handler =
                new WebSocketClientHandler(
                        WebSocketClientHandshakerFactory.newHandshaker(
                                uri, WebSocketVersion.V13, null, true, new DefaultHttpHeaders()));

        Bootstrap b = new Bootstrap();
        b.group(group)
         .channel(NioSocketChannel.class)
         .handler(new ChannelInitializer<SocketChannel>() {
             @Override
             protected void initChannel(SocketChannel ch) {
                 ChannelPipeline p = ch.pipeline();
                 if (sslCtx != null) {
                     p.addLast(sslCtx.newHandler(ch.alloc(), host, port));
                 }
                 p.addLast(
                         new HttpClientCodec(),
                         new HttpObjectAggregator(8192),
                         WebSocketClientCompressionHandler.INSTANCE,
                         handler);
             }
         });

        Channel ch = b.connect(uri.getHost(), port).sync().channel();
        handler.handshakeFuture().sync();

        BufferedReader console = new BufferedReader(new InputStreamReader(System.in));
        while (true) {
            String msg = console.readLine();
            if (msg == null) {
                break;
            } else if ("bye".equals(msg.toLowerCase())) {
                ch.writeAndFlush(new CloseWebSocketFrame());
                ch.closeFuture().sync();
                break;
            } else if ("ping".equals(msg.toLowerCase())) {
                WebSocketFrame frame = new PingWebSocketFrame(Unpooled.wrappedBuffer(new byte[] { 8, 1, 8, 1 }));
                ch.writeAndFlush(frame);
            } else {
                WebSocketFrame frame = new TextWebSocketFrame(msg);
                ch.writeAndFlush(frame);
            }
        }
    } finally {
        group.shutdownGracefully();
    }
}
}

public class WebSocketClientHandler extends SimpleChannelInboundHandler<Object> {

private final WebSocketClientHandshaker handshaker;
private ChannelPromise handshakeFuture;

public WebSocketClientHandler(WebSocketClientHandshaker handshaker) {
    this.handshaker = handshaker;
}

public ChannelFuture handshakeFuture() {
    return handshakeFuture;
}

@Override
public void handlerAdded(ChannelHandlerContext ctx) {
    handshakeFuture = ctx.newPromise();
}

@Override
public void channelActive(ChannelHandlerContext ctx) {
    handshaker.handshake(ctx.channel());
}

@Override
public void channelInactive(ChannelHandlerContext ctx) {
    System.out.println("WebSocket Client disconnected!");
}

@Override
public void channelRead0(ChannelHandlerContext ctx, Object msg) throws Exception {
    Channel ch = ctx.channel();
    if (!handshaker.isHandshakeComplete()) {
        handshaker.finishHandshake(ch, (FullHttpResponse) msg);
        System.out.println("WebSocket Client connected!");
        handshakeFuture.setSuccess();
        return;
    }

    if (msg instanceof FullHttpResponse) {
        FullHttpResponse response = (FullHttpResponse) msg;
        throw new IllegalStateException(
                "Unexpected FullHttpResponse (getStatus=" + response.status() +
                        ", content=" + response.content().toString(CharsetUtil.UTF_8) + ')');
    }

    WebSocketFrame frame = (WebSocketFrame) msg;
    if (frame instanceof TextWebSocketFrame) {
        TextWebSocketFrame textFrame = (TextWebSocketFrame) frame;
        System.out.println("WebSocket Client received message: " + textFrame.text());
    } else if (frame instanceof PongWebSocketFrame) {
        System.out.println("WebSocket Client received pong");
    } else if (frame instanceof CloseWebSocketFrame) {
        System.out.println("WebSocket Client received closing");
        ch.close();
    }
}

@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
    cause.printStackTrace();
    if (!handshakeFuture.isDone()) {
        handshakeFuture.setFailure(cause);
    }
    ctx.close();
}
}