用netty框架写一个socks代理

好的，以下是使用 Netty 框架编写 SOCKS 代理的示例代码：

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.socksx.v5.DefaultSocks5CommandRequest;
import io.netty.handler.codec.socksx.v5.DefaultSocks5InitialRequest;
import io.netty.handler.codec.socksx.v5.Socks5AddressType;
import io.netty.handler.codec.socksx.v5.Socks5ClientEncoder;
import io.netty.handler.codec.socksx.v5.Socks5CommandRequest;
import io.netty.handler.codec.socksx.v5.Socks5CommandResponse;
import io.netty.handler.codec.socksx.v5.Socks5InitialRequest;
import io.netty.handler.codec.socksx.v5.Socks5InitialResponse;
import io.netty.handler.codec.socksx.v5.Socks5PasswordAuthRequest;
import io.netty.handler.codec.socksx.v5.Socks5PasswordAuthResponse;
import io.netty.handler.codec.socksx.v5.Socks5ServerEncoder;
import io.netty.handler.codec.socksx.v5.Socks5UserPasswordAuthRequest;
import io.netty.handler.codec.socksx.v5.Socks5UserPasswordAuthResponse;
import io.netty.util.CharsetUtil;

public class SocksProxyClient {

    private static final String SOCKS_HOST = "127.0.0.1";
    private static final int SOCKS_PORT = 1080;
    private static final String REMOTE_HOST = "www.google.com";
    private static final int REMOTE_PORT = 80;

    public static void main(String[] args) throws Exception {
        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 {
                     ch.pipeline().addLast(new Socks5ClientEncoder(Socks5AddressType.DOMAIN));
                     ch.pipeline().addLast(new SocksProxyClientHandler());
                 }
             });

            ChannelFuture f = b.connect(SOCKS_HOST, SOCKS_PORT).sync();
            f.channel().closeFuture().sync();
        } finally {
            group.shutdownGracefully();
        }
    }

    private static class SocksProxyClientHandler extends ChannelInboundHandlerAdapter {

        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
            // Send initial SOCKS5 handshake request
            ctx.writeAndFlush(new DefaultSocks5InitialRequest(Socks5AuthMethod.NO_AUTH));

            // Send SOCKS5 command request to connect to remote host
            Socks5CommandRequest cmdRequest = new DefaultSocks5CommandRequest(
                    Socks5CommandRequest.CmdType.CONNECT,
                    Socks5AddressType.DOMAIN,
                    REMOTE_HOST,
                    REMOTE_PORT);
            ctx.writeAndFlush(cmdRequest);
        }

        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
            if (msg instanceof Socks5InitialResponse) {
                // Handle SOCKS5 initial response
                Socks5InitialResponse initResponse = (Socks5InitialResponse) msg;
                if (initResponse.authMethod() == Socks5AuthMethod.PASSWORD) {
                    // Send SOCKS5 username/password authentication request
                    ctx.writeAndFlush(new Socks5PasswordAuthRequest("username", "password"));
                }
            } else if (msg instanceof Socks5PasswordAuthResponse) {
                // Handle SOCKS5 username/password authentication response
                Socks5PasswordAuthResponse authResponse = (Socks5PasswordAuthResponse) msg;
                if (authResponse.status() == Socks5PasswordAuthStatus.SUCCESS) {
                    // Send SOCKS5 command request to connect to remote host
                    Socks5CommandRequest cmdRequest = new DefaultSocks5CommandRequest(
                            Socks5CommandRequest.CmdType.CONNECT,
                            Socks5AddressType.DOMAIN,
                            REMOTE_HOST,
                            REMOTE_PORT);
                    ctx.writeAndFlush(cmdRequest);
                }
            } else if (msg instanceof Socks5CommandResponse) {
                // Handle SOCKS5 command response
                Socks5CommandResponse cmdResponse = (Socks5CommandResponse) msg;
                if (cmdResponse.status() == Socks5CommandStatus.SUCCESS) {
                    // Send HTTP request to remote host
                    Channel remoteChannel = ctx.channel();
                    remoteChannel.pipeline().remove(Socks5ServerEncoder.class);
                    remoteChannel.pipeline().addLast(new HttpProxyClientHandler());
                    String httpRequest = "GET / HTTP/1.1\r\n" +
                            "Host: " + REMOTE_HOST + "\r\n" +
                            "Connection: close\r\n\r\n";
                    remoteChannel.writeAndFlush(httpRequest);
                }
            } else {
                // Handle HTTP response from remote host
                String httpResponse = (String) msg;
                System.out.println(httpResponse);
                ctx.close();
            }
        }

        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
            cause.printStackTrace();
            ctx.close();
        }
    }

    private static class HttpProxyClientHandler extends ChannelInboundHandlerAdapter {

        private StringBuilder responseBuilder = new StringBuilder();

        @Override
        public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
            String httpResponse = (String) msg;
            responseBuilder.append(httpResponse);
        }

        @Override
        public void channelInactive(ChannelHandlerContext ctx) throws Exception {
            String httpResponse = responseBuilder.toString();
            System.out.println(httpResponse);
            ctx.close();
        }

        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
            cause.printStackTrace();
            ctx.close();
        }
    }
}

这个示例代码使用 Netty 框架实现了一个 SOCKS5 代理客户端，可以连接到指定的 SOCKS5 代理服务器，并通过代理服务器连接到指定的远程主机。在连接到远程主机后，它会发送一个 HTTP GET 请求，并打印出远程主机返回的 HTTP 响应。