我是netty的新手，我正在尝试设计以下解决方案，以通过TCP将文件从服务器传输到客户端：
1. Zero copy based file transfer in case of non-ssl based transfer (Using default region of the file)
2. ChunkedFile transfer in case of SSL based transfer.
客户端-服务器文件传输以这种方式工作：
1. The client sends the location of the file to be transfered
2. Based on the location (sent by the client) the server transfers the file to the client
文件内容可以是任何内容（字符串/ image / pdf等）和任何大小。
现在，我在服务器端收到了这个 TooLongFrameException：，尽管服务器只是在解码从客户端接收的路径，用于运行下面提到的代码（服务器/客户端）。
io.netty.handler.codec.TooLongFrameException: Adjusted frame length exceeds 65536: 215542494061 - discarded
at io.netty.handler.codec.LengthFieldBasedFrameDecoder.fail(LengthFieldBasedFrameDecoder.java:522)
at io.netty.handler.codec.LengthFieldBasedFrameDecoder.failIfNecessary(LengthFieldBasedFrameDecoder.java:500)
现在，我的问题是：
请为我指明正确的方向。
FileClient：
public final class FileClient {
static final boolean SSL = System.getProperty("ssl") != null;
static final int PORT = Integer.parseInt(System.getProperty("port", SSL ? "8992" : "8023"));
static final String HOST = System.getProperty("host", "127.0.0.1");
public static void main(String[] args) throws Exception {
// Configure SSL.
final SslContext sslCtx;
if (SSL) {
SelfSignedCertificate ssc = new SelfSignedCertificate();
sslCtx = SslContextBuilder.forServer(ssc.certificate(), ssc.privateKey()).build();
} else {
sslCtx = null;
}
// Configure the client
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
b.group(group)
.channel(NioSocketChannel.class)
.option(ChannelOption.SO_KEEPALIVE, true)
.handler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
if (sslCtx != null) {
pipeline.addLast(sslCtx.newHandler(ch.alloc(), HOST, PORT));
}
pipeline.addLast("frameDecoder", new LengthFieldBasedFrameDecoder(64*1024, 0, 8));
pipeline.addLast("frameEncoder", new LengthFieldPrepender(4));
pipeline.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
pipeline.addLast(new ObjectEncoder());
pipeline.addLast( new FileClientHandler()); }
});
// Start the server.
ChannelFuture f = b.connect(HOST,PORT).sync();
// Wait until the server socket is closed.
f.channel().closeFuture().sync();
} finally {
// Shut down all event loops to terminate all threads.
group.shutdownGracefully();
}
}
}
FileClientHandler：
public class FileClientHandler extends ChannelInboundHandlerAdapter{
@Override
public void channelActive(ChannelHandlerContext ctx) {
String filePath = "/Users/Home/Documents/Data.pdf";
ctx.writeAndFlush(Unpooled.wrappedBuffer(filePath.getBytes()));
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
System.out.println("File Client Handler Read method...");
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
}
}
FileServer：
/**
* Server that accept the path of a file and echo back its content.
*/
public final class FileServer {
static final boolean SSL = System.getProperty("ssl") != null;
static final int PORT = Integer.parseInt(System.getProperty("port", SSL ? "8992" : "8023"));
public static void main(String[] args) throws Exception {
// Configure SSL.
final SslContext sslCtx;
if (SSL) {
SelfSignedCertificate ssc = new SelfSignedCertificate();
sslCtx = SslContextBuilder.forServer(ssc.certificate(), ssc.privateKey()).build();
} else {
sslCtx = null;
}
// Configure the server.
EventLoopGroup bossGroup = new NioEventLoopGroup(1);
EventLoopGroup workerGroup = new NioEventLoopGroup();
try {
ServerBootstrap b = new ServerBootstrap();
b.group(bossGroup, workerGroup).channel(NioServerSocketChannel.class)
.option(ChannelOption.SO_KEEPALIVE, true).handler(new LoggingHandler(LogLevel.INFO))
.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
public void initChannel(SocketChannel ch) throws Exception {
ChannelPipeline pipeline = ch.pipeline();
if (sslCtx != null) {
pipeline.addLast(sslCtx.newHandler(ch.alloc()));
}
pipeline.addLast("frameDecoder",new LengthFieldBasedFrameDecoder(64*1024, 0, 8));
pipeline.addLast("frameEncoder", new LengthFieldPrepender(4));
pipeline.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
pipeline.addLast(new ObjectEncoder());
pipeline.addLast(new ChunkedWriteHandler());
pipeline.addLast(new FileServerHandler());
}
});
// Start the server.
ChannelFuture f = b.bind(PORT).sync();
// Wait until the server socket is closed.
f.channel().closeFuture().sync();
} finally {
bossGroup.shutdownGracefully();
workerGroup.shutdownGracefully();
}
}
}
FileServerHandler：
public class FileServerHandler extends ChannelInboundHandlerAdapter {
@Override
public void channelRead(ChannelHandlerContext ctx, Object obj) throws Exception {
RandomAccessFile raf = null;
long length = -1;
try {
ByteBuf buff = (ByteBuf)obj;
byte[] bytes = new byte[buff.readableBytes()];
buff.readBytes(bytes);
String msg = new String(bytes);
raf = new RandomAccessFile(msg, "r");
length = raf.length();
} catch (Exception e) {
ctx.writeAndFlush("ERR: " + e.getClass().getSimpleName() + ": " + e.getMessage() + '\n');
return;
} finally {
if (length < 0 && raf != null) {
raf.close();
}
}
if (ctx.pipeline().get(SslHandler.class) == null) {
// SSL not enabled - can use zero-copy file transfer.
ctx.writeAndFlush(new DefaultFileRegion(raf.getChannel(), 0, length));
} else {
// SSL enabled - cannot use zero-copy file transfer.
ctx.writeAndFlush(new ChunkedFile(raf));
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
cause.printStackTrace();
System.out.println("Exception server.....");
}
}
我引用了Netty In Action和来自here的代码示例
答案 0 :(得分：1)
您的服务器/客户端有很多问题。首先是SSL，对于客户端，您不需要为服务器初始化SslContext，而是可以执行以下操作：
sslCtx = SslContextBuilder.forClient().trustManager(InsecureTrustManagerFactory.INSTANCE).build();
在服务器端，您使用的SelfSignedCertificate本身并没有错，但要提醒您，它仅应用于调试目的，而不能用于生产。另外，不建议使用ChannelOption.SO_KEEPALIVE，因为keepalive间隔取决于操作系统。此外，您已将Object En-/Decoder添加到管道中，这种情况对您没有任何帮助，因此可以将其删除。
由于参数 list 不完整和错误，您还配置了LengthFieldBasedFrameDecoder错误。在netty docs中，您需要定义lengthFieldLength和initialBytesToStrip的构造函数版本。除了不剥离长度字段外，您还定义了错误的lengthFieldLength，它应该与LengthFieldPrepender的{{1}}相同，为4个字节。总之，您可以使用如下构造函数：
lengthFieldLength在您的两个处理程序中，在对new LengthFieldBasedFrameDecoder(64 * 1024, 0, 4, 0, 4)
进行编码/解码时都没有指定Charset，这可能会导致问题，因为如果未定义“ Charset”，则将使用系统默认值变化。您可以执行以下操作：
String另外，如果没有将//to encode the String
string.getBytes(StandardCharsets.UTF_8);
//to decode the String
new String(bytes, StandardCharsets.UTF_8);
添加到管道中，那么您尝试使用DefaultFileRegion，如果您不添加SslHandler会很好，因为它们需要内存副本，因此可以使用要发送的byte []的长度添加到length字段。此外，我建议使用LengthFieldHandler而不是ChunkedNioFile，因为它是无阻塞的，这总是一件好事。您可以这样：
ChunkedFile关于如何{em>解码 new ChunkedNioFile(randomAccessFile.getChannel())
的最后一件事，因为它被分成几块，您可以使用简单的OutputStream简单地将它们拼凑在一起。这是我的旧文件处理程序：
ChunkedFile