java netty Ntrip 代码

以下是一个简单的 Java Netty 实现的 Ntrip 客户端的示例代码：

import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.http.DefaultFullHttpRequest;
import io.netty.handler.codec.http.DefaultHttpHeaders;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpClientCodec;
import io.netty.handler.codec.http.HttpContent;
import io.netty.handler.codec.http.HttpContentDecompressor;
import io.netty.handler.codec.http.HttpHeaderNames;
import io.netty.handler.codec.http.HttpHeaderValues;
import io.netty.handler.codec.http.HttpMethod;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpRequestEncoder;
import io.netty.handler.codec.http.HttpResponseDecoder;
import io.netty.handler.codec.http.HttpVersion;
import io.netty.handler.timeout.ReadTimeoutHandler;
import io.netty.util.CharsetUtil;

import java.net.URI;
import java.util.concurrent.TimeUnit;

public class NtripClient {

    private static final String HOST = "your-ntrip-server.com";
    private static final int PORT = 2101;
    private static final String MOUNT_POINT = "your-mount-point";
    private static final String USER_AGENT = "NTRIP Java Client";
    private static final String USERNAME = "your-username";
    private static final String PASSWORD = "your-password";
    private static final int READ_TIMEOUT_SECONDS = 180;

    public static void main(String[] args) throws Exception {
        Bootstrap bootstrap = new Bootstrap();
        bootstrap.group(new NioEventLoopGroup())
                .channel(NioSocketChannel.class)
                .option(ChannelOption.SO_KEEPALIVE, true)
                .handler(new NtripClientInitializer());

        ChannelFuture future = bootstrap.connect(HOST, PORT).sync();
        future.channel().closeFuture().sync();
    }

    private static class NtripClientInitializer extends ChannelInitializer<SocketChannel> {
        @Override
        protected void initChannel(SocketChannel ch) throws Exception {
            ChannelPipeline pipeline = ch.pipeline();
            pipeline.addLast(new HttpResponseDecoder());
            pipeline.addLast(new HttpClientCodec());
            pipeline.addLast(new HttpContentDecompressor());
            pipeline.addLast(new HttpObjectAggregator(1048576));
            pipeline.addLast(new HttpRequestEncoder());
            pipeline.addLast(new ReadTimeoutHandler(READ_TIMEOUT_SECONDS, TimeUnit.SECONDS));
            pipeline.addLast(new NtripClientHandler());
        }
    }

    private static class NtripClientHandler extends SimpleChannelInboundHandler<FullHttpResponse> {
        @Override
        protected void channelRead0(ChannelHandlerContext ctx, FullHttpResponse response) throws Exception {
            if (response.status().code() == 401) {
                System.out.println("Authentication required. Sending login credentials.");
                ByteBuf content = response.content();
                String realm = extractChallengeParameter(content.toString(CharsetUtil.UTF_8), "realm");
                String nonce = extractChallengeParameter(content.toString(CharsetUtil.UTF_8), "nonce");
                String qop = extractChallengeParameter(content.toString(CharsetUtil.UTF_8), "qop");
                String nc = "00000001";
                String cnonce = "abcdefg";
                String uri = "/" + MOUNT_POINT;
                String ha1 = md5sum(USERNAME + ":" + realm + ":" + PASSWORD);
                String ha2 = md5sum("GET:" + uri);
                String responseValue = md5sum(ha1 + ":" + nonce + ":" + nc + ":" + cnonce + ":" + qop + ":" + ha2);
                DefaultHttpHeaders headers = new DefaultHttpHeaders();
                headers.set(HttpHeaderNames.USER_AGENT, USER_AGENT);
                headers.set(HttpHeaderNames.HOST, HOST);
                headers.set(HttpHeaderNames.CONNECTION, HttpHeaderValues.KEEP_ALIVE);
                headers.set(HttpHeaderNames.AUTHORIZATION, "Digest username=\"" + USERNAME + "\", realm=\"" + realm + "\", nonce=\"" + nonce + "\", uri=\"" + uri + "\", qop=" + qop + ", nc=" + nc + ", cnonce=\"" + cnonce + "\", response=\"" + responseValue + "\"");
                DefaultFullHttpRequest request = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.GET, "/" + MOUNT_POINT, headers);
                ctx.writeAndFlush(request);
            } else if (response.status().code() == 200) {
                System.out.println("Connected. Waiting for data...");
            } else {
                System.out.println("Unexpected response from server: " + response);
                ctx.close();
            }
        }

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

        private String extractChallengeParameter(String challenge, String parameter) {
            String[] parts = challenge.split(",");
            for (String part : parts) {
                String[] subParts = part.split("=");
                if (subParts.length == 2 && subParts[0].trim().equals(parameter)) {
                    return subParts[1].trim().replaceAll("\"", "");
                }
            }
            return null;
        }

        private String md5sum(String input) throws Exception {
            MessageDigest digest = MessageDigest.getInstance("MD5");
            digest.update(input.getBytes(CharsetUtil.UTF_8));
            byte[] md5sum = digest.digest();
            StringBuilder builder = new StringBuilder();
            for (byte b : md5sum) {
                builder.append(Integer.toString((b & 0xff) + 0x100, 16).substring(1));
            }
            return builder.toString();
        }
    }
}

该示例使用 Netty 实现了一个 Ntrip 客户端，可以连接到指定的 Ntrip 服务器并发送身份验证信息以获取数据。代码使用了 Netty 的 HTTP 编解码器来处理 HTTP 报文，以及 Netty 的超时处理器来处理读取超时。注意，该示例仅用于演示目的，实际使用时需要根据具体情况进行适当修改。