修复组播无法接收

pom.xml

@@ -18,7 +18,7 @@
         <dependency>
             <groupId>io.netty</groupId>
             <artifactId>netty-all</artifactId>
-            <version>4.1.68.Final</version>
+            <version>4.1.110.Final</version>
         </dependency>
         <dependency>
             <groupId>org.projectlombok</groupId>

src/main/java/cn/x47/RIPService.java

@@ -8,34 +8,46 @@ import cn.x47.service.RIPClient;
 import cn.x47.service.RIPServer;
 
 import java.net.InetAddress;
+import java.net.SocketException;
+import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.List;
-import java.util.concurrent.*;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
 
 public class RIPService {
 
     public static void main(String[] args) throws Exception {
         // 启动服务器
-        RIPServer server = new RIPServer();
-        new Thread(() -> {
-            try {
-                server.start();
-            } catch (InterruptedException e) {
-                e.printStackTrace();
-            }
-        }).start();
+        if (Config.startServer) {
+            RIPServer server = new RIPServer();
+            new Thread(() -> {
+                try {
+                    server.start();
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                } catch (SocketException | UnknownHostException e) {
+                    throw new RuntimeException(e);
+                }
+            }).start();
+            System.out.println("服务端已经启动");
+        }
 
-        // 启动客户端
-        RIPClient client = new RIPClient();
+        if (Config.startClient) {
+            // 启动客户端
+            RIPClient client = new RIPClient();
+            // 定期发送路由更新
+            ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
+            scheduler.scheduleAtFixedRate(() -> {
+                RIPPacket packet = createRipResponsePacket(Config.RIP_VERSION);
+                client.sendRipPacket(packet);
+                System.out.println("客户端 发送了一次消息");
+            }, 0, 10, TimeUnit.SECONDS);
+            System.out.println("客户端已经启动");
+        }
 
-        // 定期发送路由更新
-        ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
-        scheduler.scheduleAtFixedRate(() -> {
-            RIPPacket packet = createRipResponsePacket(Config.RIP_VERSION);
-            client.sendRipPacket(packet);
-        }, 0, 30, TimeUnit.SECONDS);
-
-//         主线程等待
+        // 主线程等待
         Thread.currentThread().join();
     }
 
@@ -44,9 +56,9 @@ public class RIPService {
 
         try {
             // 示例：添加本地路由条目
-            InetAddress localAddress = InetAddress.getByName("192.168.100.0");
-            InetAddress subnetMask = InetAddress.getByName("255.255.255.0");
-            InetAddress nextHop = InetAddress.getByName("192.168.123.45");
+            InetAddress localAddress = InetAddress.getByName("10.110.80.52");
+            InetAddress subnetMask = InetAddress.getByName("255.255.255.255");
+            InetAddress nextHop = InetAddress.getByName("0.0.0.0");
 
             RIPEntry entry = new RIPEntry();
             entry.setAddressFamily((short) 2); // AF_INET

src/main/java/cn/x47/config/Config.java

@@ -3,4 +3,6 @@ package cn.x47.config;
 public class Config {
     // 设置协议版本，1 表示 RIP v1，2 表示 RIP v2
     public static final byte RIP_VERSION = 2;
+    public static final boolean startServer = true;
+    public static final boolean startClient = true;
 }

src/main/java/cn/x47/handle/RIPPacketDecoder.java

@@ -4,12 +4,14 @@ package cn.x47.handle;
 import cn.x47.model.RIPEntry;
 import cn.x47.model.RIPPacket;
 import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufUtil;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.socket.DatagramPacket;
 import io.netty.handler.codec.MessageToMessageDecoder;
 
 import java.net.InetAddress;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 /**
@@ -28,37 +30,34 @@ public class RIPPacketDecoder extends MessageToMessageDecoder<DatagramPacket> {
         List<RIPEntry> entries = new ArrayList<>();
         while (buf.readableBytes() >= 20) {
             RIPEntry entry = new RIPEntry();
-            entry.setAddressFamily((short) buf.readUnsignedShort());
-
-            if (ripPacket.getVersion() == 2) {
-                entry.setRouteTag((short) buf.readUnsignedShort());
-            } else {
-                entry.setRouteTag((short) 0);
-            }
+            entry.setAddressFamily(buf.readShort());
+            entry.setRouteTag(buf.readShort());
 
             byte[] ipBytes = new byte[4];
             buf.readBytes(ipBytes);
             entry.setIpAddress(InetAddress.getByAddress(ipBytes));
 
-            if (ripPacket.getVersion() == 2) {
-                buf.readBytes(ipBytes);
-                entry.setSubnetMask(InetAddress.getByAddress(ipBytes));
-                buf.readBytes(ipBytes);
-                entry.setNextHop(InetAddress.getByAddress(ipBytes));
-            } else {
+            buf.readBytes(ipBytes);
+            entry.setSubnetMask(InetAddress.getByAddress(ipBytes));
+            buf.readBytes(ipBytes);
+            entry.setNextHop(InetAddress.getByAddress(ipBytes));
+            if (ripPacket.getVersion() == 1) {
                 // 对于 RIP v1，子网掩码和下一跳需要推断或设为默认值
                 entry.setSubnetMask(InetAddress.getByName("255.255.255.0")); // 示例，实际应根据 IP 类推断
+
+            }
+
+            byte[] address = entry.getNextHop().getAddress();
+            byte[] address1 = InetAddress.getByName("0.0.0.0").getAddress();
+
+            if(Arrays.equals(address, address1)) {
                 entry.setNextHop(packet.sender().getAddress());
             }
 
-            long metric = buf.readUnsignedInt();
-            entry.setMetric(metric);
-
+            entry.setMetric((int) buf.readUnsignedInt());
             entries.add(entry);
         }
         ripPacket.setEntries(entries);
-        ripPacket.setSenderAddress(packet.sender()); // 设置发送者地址
         out.add(ripPacket);
     }
-
 }

src/main/java/cn/x47/handle/RIPPacketEncoder.java

@@ -25,18 +25,21 @@ public class RIPPacketEncoder extends MessageToMessageEncoder<RIPPacket> {
 
         // 编码路由条目
         for (RIPEntry entry : msg.getEntries()) {
-            buf.writeShort(entry.getAddressFamily() & 0xFFFF);
+            buf.writeShort(entry.getAddressFamily());
             if (msg.getVersion() == 2) {
-                buf.writeShort(entry.getRouteTag() & 0xFFFF);
+                buf.writeShort(entry.getRouteTag());
+            } else if (msg.getVersion() == 1) {
+                buf.writeShort(0);
             }
             buf.writeBytes(entry.getIpAddress().getAddress());
-
             if (msg.getVersion() == 2) {
                 buf.writeBytes(entry.getSubnetMask().getAddress());
                 buf.writeBytes(entry.getNextHop().getAddress());
+            } else if (msg.getVersion() == 1) {
+                buf.writeInt(0);
+                buf.writeInt(0);
             }
-
-            buf.writeInt((int) entry.getMetric() & 0xFFFFFFFF);
+            buf.writeInt(entry.getMetric());
         }
 
         // 根据版本选择目标地址
@@ -49,5 +52,4 @@ public class RIPPacketEncoder extends MessageToMessageEncoder<RIPPacket> {
 
         out.add(new DatagramPacket(buf, recipient));
     }
-
 }

src/main/java/cn/x47/handle/RIPServerHandler.java

@@ -1,186 +1,34 @@
 package cn.x47.handle;
 
+
 import cn.x47.model.RIPEntry;
 import cn.x47.model.RIPPacket;
 import cn.x47.service.RoutingTable;
-import io.netty.buffer.ByteBuf;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.SimpleChannelInboundHandler;
-import io.netty.channel.socket.DatagramPacket;
-
-import java.net.InetAddress;
-import java.net.InetSocketAddress;
-import java.nio.ByteOrder;
-import java.util.ArrayList;
-import java.util.List;
 
 public class RIPServerHandler extends SimpleChannelInboundHandler<RIPPacket> {
 
     @Override
     protected void channelRead0(ChannelHandlerContext ctx, RIPPacket msg) throws Exception {
-        InetSocketAddress senderAddress = msg.getSenderAddress();
-        byte version = msg.getVersion();
-        System.out.println(msg.toString());
-
-//        if (msg.getCommand() == 2) { // Response
-//            for (RIPEntry entry : msg.getEntries()) {
-//                // 更新本地路由表
-//                updateRoutingTable(entry, senderAddress, version);
-//            }
-//        } else if (msg.getCommand() == 1) { // Request
-//            // 处理请求，发送响应包
-//            handleRequest(ctx, msg);
-//        }
-    }
-
-    private void handleRequest(ChannelHandlerContext ctx, RIPPacket requestPacket) throws Exception {
-        List<RIPEntry> requestEntries = requestPacket.getEntries();
-        byte version = requestPacket.getVersion();
-
-        boolean isGeneralRequest = false;
-
-        // 检查是否为一般请求
-        if (requestEntries.size() == 1) {
-            RIPEntry entry = requestEntries.get(0);
-            if (entry.getIpAddress().getHostAddress().equals("0.0.0.0") && entry.getMetric() == 16) {
-                isGeneralRequest = true;
+        if (msg.getCommand() == 2) { // Response
+            for (RIPEntry entry : msg.getEntries()) {
+                // 更新本地路由表
+                updateRoutingTable(entry);
             }
-        }
-
-        RIPPacket responsePacket = new RIPPacket();
-        responsePacket.setCommand((byte) 2); // Response
-        responsePacket.setVersion(version); // 与请求的版本一致
-        responsePacket.setUnused((short) 0);
-        List<RIPEntry> responseEntries = new ArrayList<>();
-
-        if (isGeneralRequest) {
-            // 一般请求，返回整个路由表
-            responseEntries.addAll(getAllRoutingEntries(version));
-        } else {
-            // 特定请求，逐一处理请求的条目
-            for (RIPEntry requestEntry : requestEntries) {
-                RIPEntry route = getRoutingEntry(requestEntry.getIpAddress());
-                if (route != null) {
-                    responseEntries.add(route);
-                } else {
-                    // 如果没有该路由，返回度量值为 16（无限）
-                    RIPEntry unreachableEntry = new RIPEntry();
-                    unreachableEntry.setAddressFamily(requestEntry.getAddressFamily());
-                    unreachableEntry.setIpAddress(requestEntry.getIpAddress());
-                    unreachableEntry.setMetric(16);
-
-                    if (version == 2) {
-                        unreachableEntry.setRouteTag((short) 0);
-                        unreachableEntry.setSubnetMask(requestEntry.getSubnetMask());
-                        unreachableEntry.setNextHop(InetAddress.getByName("0.0.0.0"));
-                    }
-
-                    responseEntries.add(unreachableEntry);
-                }
-            }
-        }
-
-        // 构建响应包
-        responsePacket.setEntries(responseEntries);
-
-        // 获取发送者的地址
-        InetSocketAddress recipient = requestPacket.getSenderAddress();
-
-        // 发送响应包
-        ByteBuf buf = ctx.alloc().buffer().order(ByteOrder.BIG_ENDIAN); // 确保使用大端序
-        encodeRIPPacket(responsePacket, buf);
-
-        DatagramPacket responseDatagram = new DatagramPacket(buf, recipient);
-        ctx.writeAndFlush(responseDatagram);
-    }
-
-    private void encodeRIPPacket(RIPPacket msg, ByteBuf buf) throws Exception {
-        // 编码命令和版本
-        buf.writeByte(msg.getCommand());
-        buf.writeByte(msg.getVersion());
-        buf.writeShort(0); // unused 字段
-
-        // 编码路由条目
-        for (RIPEntry entry : msg.getEntries()) {
-            buf.writeShort(entry.getAddressFamily());
-            if (msg.getVersion() == 2) {
-                buf.writeShort(entry.getRouteTag());
-            }
-            buf.writeBytes(entry.getIpAddress().getAddress());
-
-            if (msg.getVersion() == 2) {
-                buf.writeBytes(entry.getSubnetMask().getAddress());
-                buf.writeBytes(entry.getNextHop().getAddress());
-            }
-            buf.writeInt((int) (entry.getMetric() & 0xFFFFFFFFL));
+        } else if (msg.getCommand() == 1) { // Request
+            // 处理请求，可能需要发送响应包
+            // ...
         }
     }
 
-    private List<RIPEntry> getAllRoutingEntries(byte version) throws Exception {
-        List<RIPEntry> entries = new ArrayList<>();
-        // 从路由表中获取所有的路由条目
-        for (RIPEntry route : RoutingTable.getInstance().getRoutes().values()) {
-            RIPEntry entry = new RIPEntry();
-            entry.setAddressFamily(route.getAddressFamily());
-            entry.setIpAddress(route.getIpAddress());
-            entry.setMetric(route.getMetric());
-
-            if (version == 2) {
-                entry.setRouteTag(route.getRouteTag());
-                entry.setSubnetMask(route.getSubnetMask());
-                entry.setNextHop(route.getNextHop());
-            }
-
-            entries.add(entry);
-        }
-        return entries;
-    }
-
-    private RIPEntry getRoutingEntry(InetAddress ipAddress) throws Exception {
-        RIPEntry route = RoutingTable.getInstance().getRoute(ipAddress);
-        if (route != null) {
-            RIPEntry entry = new RIPEntry();
-            entry.setAddressFamily(route.getAddressFamily());
-            entry.setIpAddress(route.getIpAddress());
-            entry.setMetric(route.getMetric());
-
-            entry.setRouteTag(route.getRouteTag());
-            entry.setSubnetMask(route.getSubnetMask());
-            entry.setNextHop(route.getNextHop());
-
-            return entry;
-        }
-        return null;
-    }
-
-    private void updateRoutingTable(RIPEntry entry, InetSocketAddress senderAddress, byte version) throws Exception {
-        if (version == 1) {
-            // 推断下一跳为发送者的地址
-            entry.setNextHop(senderAddress.getAddress());
-            // 根据 IP 地址类别推断子网掩码
-            InetAddress ipAddress = entry.getIpAddress();
-            byte[] addressBytes = ipAddress.getAddress();
-            int firstOctet = addressBytes[0] & 0xFF;
-
-            if (firstOctet >= 0 && firstOctet <= 127) {
-                // A 类地址
-                entry.setSubnetMask(InetAddress.getByName("255.0.0.0"));
-            } else if (firstOctet >= 128 && firstOctet <= 191) {
-                // B 类地址
-                entry.setSubnetMask(InetAddress.getByName("255.255.0.0"));
-            } else if (firstOctet >= 192 && firstOctet <= 223) {
-                // C 类地址
-                entry.setSubnetMask(InetAddress.getByName("255.255.255.0"));
-            } else {
-                // 非法地址，忽略
-                System.out.println("Invalid IP address in RIP Entry: " + ipAddress.getHostAddress());
-                return;
-            }
-        }
+    private void updateRoutingTable(RIPEntry entry) {
         // 实现路由表更新逻辑
+        // 这里只是示例，实际需要处理路由添加、更新、超时等逻辑
         RoutingTable.getInstance().updateRoute(entry);
         System.out.println("Updated route: " + entry.getIpAddress().getHostAddress() +
                 " via " + entry.getNextHop().getHostAddress() +
                 " metric: " + entry.getMetric());
+
     }
 }

src/main/java/cn/x47/model/RIPEntry.java

@@ -6,12 +6,13 @@ import java.net.InetAddress;
 
 @Data
 public class RIPEntry {
+    //
     private short addressFamily;
     private short routeTag;            // RIP v2 特有
     private InetAddress ipAddress;
     private InetAddress subnetMask;    // RIP v2 特有
     private InetAddress nextHop;       // RIP v2 特有
-    private long metric;
+    private int metric;
 
 
 }

src/main/java/cn/x47/model/RIPPacket.java

@@ -4,7 +4,6 @@ import lombok.AllArgsConstructor;
 import lombok.Data;
 import lombok.NoArgsConstructor;
 
-import java.net.InetSocketAddress;
 import java.util.List;
 
 @Data
@@ -15,7 +14,6 @@ public class RIPPacket {
     private byte version; // 1=RIP v1, 2=RIP v2
     private short unused = 0; // 未使用，设置为 0
     private List<RIPEntry> entries;
-    private InetSocketAddress senderAddress;
 
     // 添加构造方法和 Getter/Setter
     public RIPPacket(byte command, byte version, List<RIPEntry> entries) {

src/main/java/cn/x47/service/RIPClient.java

@@ -4,12 +4,12 @@ package cn.x47.service;
 import cn.x47.handle.RIPPacketEncoder;
 import cn.x47.model.RIPPacket;
 import io.netty.bootstrap.Bootstrap;
-import io.netty.channel.*;
-import io.netty.channel.socket.nio.NioDatagramChannel;
-import io.netty.channel.socket.DatagramChannel;
-
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelInitializer;
+import io.netty.channel.ChannelOption;
 import io.netty.channel.nio.NioEventLoopGroup;
-
+import io.netty.channel.socket.DatagramChannel;
+import io.netty.channel.socket.nio.NioDatagramChannel;
 
 
 public class RIPClient {

src/main/java/cn/x47/service/RIPServer.java

@@ -4,31 +4,75 @@ package cn.x47.service;
 import cn.x47.handle.RIPPacketDecoder;
 import cn.x47.handle.RIPServerHandler;
 import io.netty.bootstrap.Bootstrap;
-import io.netty.channel.*;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelInitializer;
+import io.netty.channel.ChannelOption;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.channel.socket.DatagramChannel;
 import io.netty.channel.socket.nio.NioDatagramChannel;
 
+import java.net.*;
+import java.util.ArrayList;
+import java.util.Enumeration;
+import java.util.List;
+
 public class RIPServer {
 
-    public void start() throws InterruptedException {
+    public void start() throws InterruptedException, UnknownHostException, SocketException {
         NioEventLoopGroup group = new NioEventLoopGroup();
         try {
             Bootstrap b = new Bootstrap();
             b.group(group)
                     .channel(NioDatagramChannel.class)
                     .option(ChannelOption.SO_BROADCAST, true)
+                    .option(ChannelOption.IP_MULTICAST_LOOP_DISABLED, true)
                     .handler(new ChannelInitializer<DatagramChannel>() {
                         @Override
                         protected void initChannel(DatagramChannel ch) throws Exception {
+
                             ch.pipeline().addLast(new RIPPacketDecoder(), new RIPServerHandler());
                         }
                     });
 
             ChannelFuture future = b.bind(520).sync();
+            // 获取并加入组播组
+            NioDatagramChannel channel = (NioDatagramChannel) future.channel();
+            InetAddress multicastAddress = InetAddress.getByName("224.0.0.9"); // 替换为你的组播地址
+
+            // 自动获取网络接口并加入组播组
+            List<NetworkInterface> multicastInterfaces = getMulticastInterfaces();
+            for (NetworkInterface networkInterface : multicastInterfaces) {
+                channel.joinGroup(new InetSocketAddress(multicastAddress, 520), networkInterface).sync();
+                System.out.println("已在接口 " + networkInterface.getName() + " 上加入组播组");
+            }
+            System.out.println("监听器已启动，正在监听端口：" + 520);
             future.channel().closeFuture().await();
         } finally {
             group.shutdownGracefully();
         }
     }
+
+    private List<NetworkInterface> getMulticastInterfaces() throws SocketException {
+        List<NetworkInterface> interfaces = new ArrayList<>();
+        Enumeration<NetworkInterface> networkInterfaces = NetworkInterface.getNetworkInterfaces();
+        while (networkInterfaces.hasMoreElements()) {
+            NetworkInterface networkInterface = networkInterfaces.nextElement();
+            if (networkInterface.isUp() && !networkInterface.isLoopback() && networkInterface.supportsMulticast()) {
+                // 检查是否有 IPv4 地址
+                Enumeration<InetAddress> addresses = networkInterface.getInetAddresses();
+                boolean hasIPv4 = false;
+                while (addresses.hasMoreElements()) {
+                    InetAddress address = addresses.nextElement();
+                    if (address instanceof Inet4Address) {
+                        hasIPv4 = true;
+                        break;
+                    }
+                }
+                if (hasIPv4) {
+                    interfaces.add(networkInterface);
+                }
+            }
+        }
+        return interfaces;
+    }
 }

src/main/java/cn/x47/service/RoutingTable.java

@@ -1,6 +1,7 @@
 package cn.x47.service;
 
 
+
 import cn.x47.model.RIPEntry;
 
 import java.net.InetAddress;
@@ -31,8 +32,4 @@ public class RoutingTable {
     public Map<InetAddress, RIPEntry> getRoutes() {
         return routes;
     }
-
-    public RIPEntry getRoute(InetAddress ipAddress) {
-        return routes.get(ipAddress);
-    }
 }

src/test/java/Connection.java

@@ -0,0 +1,285 @@
+import java.io.IOException;
+import java.io.ObjectInputStream;
+import java.io.ObjectOutputStream;
+import java.net.InetAddress;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.net.UnknownHostException;
+import java.util.*;
+
+/**
+ * Connection class takes input from the user
+ * and creates threads for the client and server
+ *
+ * @author Ankit
+ */
+public class Connection {
+
+    // Stores destination and cost to reach
+    public static HashMap<String, Integer> table;
+    // Stores local ip address
+    static String[] localIP;
+    // Stores it's neighbors
+    static ArrayList<String> neighbors;
+    //Stores destination and next hop
+    public static HashMap<String, String> hop;
+    // Subnet mask
+    public static String subnetMask = "255.255.255.0";
+
+    public static void main(String[] args) throws IOException {
+        table = new HashMap<>();
+        hop = new HashMap<>();
+        neighbors = new ArrayList<>();
+        System.out.println(InetAddress.getLocalHost() + " connection started");
+        localIP = InetAddress.getLocalHost().toString().split("/");
+        System.out.println("Updated position 1");
+        table.put(localIP[1], 0);
+        hop.put(localIP[1], localIP[1]);
+        // Starts the server
+        Server server = new Server();
+        server.start();
+
+        int length = args.length;
+        // User input for the neighbor ip and cost
+        Scanner scan = new Scanner(System.in);
+        for (int i = 0; i < length; i++) {
+            System.out.println("Enter the cost for " + args[i].toString());
+            int cost = scan.nextInt();
+            new Client(args[i], cost).start();
+        }
+        scan.close();
+    }
+
+    /**
+     * Updates the destination cost and the next hop
+     *
+     * @param temp     - routing table of neighbor
+     * @param senderIP - sender ip address
+     * @param tempHop  - Next hops of the sender
+     */
+    public static void updateTable(Map<String, Integer> temp, String senderIP, Map<String, String> tempHop) {
+        // updates the table if neighbor has smaller value
+        if (table.containsKey(senderIP) && temp.containsKey(localIP[1])) {
+            if (table.get(senderIP) > temp.get(localIP[1])) {
+                table.put(senderIP, temp.get(localIP[1]));
+                if (tempHop.get(localIP[1]).equals(localIP[1])) {
+                    hop.put(senderIP, senderIP);
+                } else {
+                    for (int i = 0; i < neighbors.size(); i++) {
+                        if (!neighbors.get(i).equals(senderIP)) {
+                            hop.put(senderIP, neighbors.get(i));
+                        }
+                    }
+                }
+
+            }
+        }
+
+        // Add the neighbor if neighbor has its entry
+        if (!table.containsKey(senderIP)) {
+            table.put(senderIP, temp.get(localIP[1]));
+            hop.put(senderIP, senderIP);
+        }
+
+        @SuppressWarnings("rawtypes")
+        Iterator it = temp.entrySet().iterator();
+        while (it.hasNext()) {
+            @SuppressWarnings("rawtypes")
+            Map.Entry pair = (Map.Entry) it.next();
+            String ip = pair.getKey().toString();
+            if (!table.containsKey(ip)) {
+                table.put(ip, Integer.parseInt(pair.getValue().toString())
+                        + table.get(senderIP));
+                hop.put(ip, senderIP);
+            } else {
+                if (table.get(ip) > (Integer.parseInt(pair.getValue()
+                        .toString()) + table.get(senderIP))) {
+                    table.put(
+                            ip,
+                            (Integer.parseInt(pair.getValue().toString()) + table
+                                    .get(senderIP)));
+                    hop.put(ip, senderIP);
+                }
+            }
+        }
+    }
+
+    /**
+     * Displays the desired output i.e.
+     * Destination, subnet mask, cost and next hop
+     */
+    public static void display() {
+        @SuppressWarnings("rawtypes")
+        Iterator it = table.entrySet().iterator();
+        System.out.println("------ UPDATED TABLE -----");
+        System.out.println("Destination" + '\t' + "Subnet Mask" + '\t' + "Cost" + '\t' + "Next Hop");
+        while (it.hasNext()) {
+            @SuppressWarnings("rawtypes")
+            Map.Entry pair = (Map.Entry) it.next();
+            String[] ipSubParts = pair.getKey().toString().split("\\.");
+            String[] subnetSubParts = subnetMask.split("\\.");
+            String[] netID = new String[4];
+            for (int i = 0; i < ipSubParts.length; i++) {
+                netID[i] = Integer.toString((Integer.parseInt(ipSubParts[i]) & Integer.parseInt(subnetSubParts[i])));
+            }
+            String networkID = netID[0] + "." + netID[1] + "." + netID[2] + "." + netID[3];
+            // Desired output displayed
+            System.out.println(networkID + '\t' + subnetMask + '\t' + pair.getValue() + '\t' + hop.get(pair.getKey().toString()));
+        }
+        System.out.println();
+        System.out.println("----------------------------------------------");
+    }
+
+}
+
+/**
+ * Server class accepts the connection from the neighbors
+ * It waits for neighbors input, updates table
+ * and sends updated table
+ *
+ * @author Ankit
+ */
+class Server extends Thread {
+
+    private static ServerSocket server;
+    private Socket connection;
+    ObjectInputStream input;
+    ObjectOutputStream output;
+
+    public Server() throws IOException {
+        server = new ServerSocket(6969);
+    }
+
+    public void run() {
+        try {
+            accept();
+        } catch (UnknownHostException | ClassNotFoundException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public void accept() throws UnknownHostException, ClassNotFoundException {
+        try {
+            int count = 0;
+            while (count < 2) {
+                count++;
+                System.out.println(InetAddress.getLocalHost()
+                        + " is waiting for connection " + count);
+                // accepts the connection from the neighbors
+                connection = server.accept();
+                System.out.println(InetAddress.getLocalHost()
+                        + " connected to " + connection.getInetAddress());
+                String[] connectionIP = connection.getInetAddress().toString()
+                        .split("/");
+                Connection.neighbors.add(connectionIP[1]);
+                output = new ObjectOutputStream(connection.getOutputStream());
+                input = new ObjectInputStream(connection.getInputStream());
+
+                // Creates new thread to interact with the client
+                new Thread(new Runnable() {
+                    @SuppressWarnings({"rawtypes", "unchecked"})
+                    @Override
+                    public void run() {
+                        while (true) {
+                            try {
+                                HashMap<HashMap<String, Integer>, HashMap<String, String>> receiver;
+                                // reads the input from the neighbor
+                                receiver = (HashMap<HashMap<String, Integer>, HashMap<String, String>>) input.readObject();
+                                HashMap<String, Integer> temp = (HashMap<String, Integer>) receiver.keySet().toArray()[0];
+                                HashMap<String, String> tempHop = receiver.get(temp);
+                                @SuppressWarnings("unused")
+                                Iterator it = temp.entrySet().iterator();
+                                Connection.updateTable(temp, connectionIP[1], tempHop);
+                                HashMap<HashMap<String, Integer>, HashMap<String, String>> sender;
+                                sender = new HashMap<HashMap<String, Integer>, HashMap<String, String>>();
+                                sender.put(Connection.table, Connection.hop);
+                                // sends the updated table to its neighbors
+                                output.writeObject(sender);
+                                output.reset();
+                                Connection.display();
+                                Thread.sleep(1000);
+                            } catch (Exception e) {
+                                System.exit(0);
+                            }
+                        }
+                    }
+                }).start();
+
+            }
+        } catch (IOException e) {
+            System.exit(0);
+        }
+    }
+}
+
+/**
+ * Client asks for the connection to the server
+ * It sends current routing table and recieves the updated routing table
+ *
+ * @author Ankit
+ */
+class Client extends Thread {
+
+    Socket connection;
+    String ipAddress = "";
+    int cost;
+    ObjectInputStream input;
+    ObjectOutputStream output;
+
+    public Client(String ip, int cost) throws IOException {
+        ipAddress = ip;
+        this.cost = cost;
+    }
+
+    @SuppressWarnings({"unused", "unchecked"})
+    public void run() {
+        try {
+            // connects to the server
+            connection = new Socket(ipAddress, 6969);
+            Connection.neighbors.add(ipAddress);
+            output = new ObjectOutputStream(connection.getOutputStream());
+            input = new ObjectInputStream(connection.getInputStream());
+            System.out.println(InetAddress.getLocalHost().toString()
+                    + " Connected to: " + ipAddress + " with cost: " + cost);
+            if (Connection.table.containsKey(ipAddress)) {
+                if (Connection.table.get(ipAddress) > cost) {
+                    Connection.table.put(ipAddress, cost);
+                    Connection.hop.put(ipAddress, ipAddress);
+                }
+            } else {
+                Connection.table.put(ipAddress, cost);
+                Connection.hop.put(ipAddress, ipAddress);
+            }
+
+            while (true) {
+                Connection.display();
+                HashMap<HashMap<String, Integer>, HashMap<String, String>> sender;
+                sender = new HashMap<HashMap<String, Integer>, HashMap<String, String>>();
+                sender.put(Connection.table, Connection.hop);
+                // sends updated cost and next hop table to the neighbor
+                output.writeObject(sender);
+                output.reset();
+
+                HashMap<HashMap<String, Integer>, HashMap<String, String>> receiver;
+                // reads updated cost and next hop table from neighbor
+                receiver = (HashMap<HashMap<String, Integer>, HashMap<String, String>>) input.readObject();
+                HashMap<String, Integer> temp = (HashMap<String, Integer>) receiver.keySet().toArray()[0];
+                HashMap<String, String> tempHop = receiver.get(temp);
+                @SuppressWarnings("rawtypes")
+                Iterator it = temp.entrySet().iterator();
+                Connection.updateTable(temp, ipAddress, tempHop);
+                Thread.sleep(1000);
+            }
+
+        } catch (UnknownHostException e) {
+            System.out.println("Cannot connect to the network: "
+                    + e.getMessage());
+        } catch (IOException e) {
+            System.exit(0);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        } catch (ClassNotFoundException e) {
+            e.printStackTrace();
+        }
+    }
+}

src/test/java/RipV1PacketBuilder.java

@@ -0,0 +1,85 @@
+import java.net.InetAddress;
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+
+public class RipV1PacketBuilder {
+
+    public static byte[] buildRipV1RequestPacket() throws IOException {
+        // 使用 ByteArrayOutputStream 和 DataOutputStream 来构建数据包
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        DataOutputStream dos = new DataOutputStream(baos);
+
+        // 1. Command (8比特) - 请求报文，值为 1
+        dos.writeByte(1);  // 请求报文
+
+        // 2. Version (8比特) - RIP v1，值为 1
+        dos.writeByte(1);  // RIP v1
+
+        // 3. Must be zero (16比特) - 保留字段，必须为零
+        dos.writeShort(0); // 保留字段，填充为零
+
+        // 4. Address Family Identifier (AFI) - 请求报文中为 0
+        dos.writeShort(0); // 请求报文的 AFI 为 0
+
+        // 5. IP Address (32比特) - 目标 IP 地址，RIP 请求报文中通常为 0.0.0.0
+        InetAddress byName = InetAddress.getByName("200.0.2.0");
+
+        // 6. Metric (32比特) - 请求报文的 Metric 为 16，表示不可达
+        dos.writeInt(16); // Metric = 16
+
+        // 转换成字节数组
+        return baos.toByteArray();
+    }
+
+    public static byte[] buildRipV1ResponsePacket() throws IOException {
+        // 使用 ByteArrayOutputStream 和 DataOutputStream 来构建数据包
+        ByteArrayOutputStream baos = new ByteArrayOutputStream();
+        DataOutputStream dos = new DataOutputStream(baos);
+
+        // 1. Command (8比特) - 响应报文，值为 2
+        dos.writeByte(2);  // 响应报文
+
+        // 2. Version (8比特) - RIP v1，值为 1
+        dos.writeByte(1);  // RIP v1
+
+        // 3. Must be zero (16比特) - 保留字段，必须为零
+        dos.writeShort(0); // 保留字段，填充为零
+
+        // 4. Address Family Identifier (AFI) - 请求报文中为 0
+        dos.writeShort(2); // 响应报文的 AFI 对于 IPv4 为 2
+
+        dos.writeShort(0);
+
+        // 5. IP Address (32比特) - 目标 IP 地址，假设响应报文中为某个 IP
+        InetAddress byName = InetAddress.getByName("200.0.2.0");
+        printByteArray(byName.getAddress());
+
+        dos.write(byName.getAddress()); // 192.168.0.1（IPv4 地址）
+
+        // 6. Metric (32比特) - 路由的 Metric
+        dos.writeInt(1); // 假设 Metric 为 1
+
+        // 转换成字节数组
+        return baos.toByteArray();
+    }
+
+    public static void main(String[] args) throws IOException {
+        byte[] requestPacket = buildRipV1RequestPacket();
+        byte[] responsePacket = buildRipV1ResponsePacket();
+
+        System.out.println("RIP v1 Request Packet: ");
+        printByteArray(requestPacket);
+
+        System.out.println("RIP v1 Response Packet: ");
+        printByteArray(responsePacket);
+    }
+
+    // 打印字节数组的辅助函数
+    private static void printByteArray(byte[] byteArray) {
+        for (byte b : byteArray) {
+            System.out.printf("%02X ", b);
+        }
+        System.out.println();
+    }
+}

src/test/java/RipV1Response.java

@@ -0,0 +1,66 @@
+import java.net.*;
+import java.io.*;
+
+public class RipV1Response {
+
+    public static void main(String[] args) {
+        try {
+            // 创建一个数据包
+            byte[] packet = createRipV1ResponsePacket();
+
+            // 创建一个UDP Socket
+//            DatagramSocket socket = new DatagramSocket();
+            // 创建一个UDP Socket，并将其绑定到指定的 IP 地址
+            DatagramSocket socket = new DatagramSocket(null);
+            socket.bind(new InetSocketAddress(InetAddress.getByName("192.168.123.45"), 520)); // 使用特定的本地 IP 地址绑定端口
+
+
+            InetAddress address = InetAddress.getByName("224.0.0.9"); // RIPv1 默认的多播地址
+
+            // 创建一个DatagramPacket并发送
+            DatagramPacket sendPacket = new DatagramPacket(packet, packet.length, address, 520); // RIPv1 默认端口 520
+            socket.send(sendPacket);
+
+            System.out.println("RIP v1 Response packet sent!");
+            socket.close();
+        } catch (Exception e) {
+            e.printStackTrace();
+        }
+    }
+
+    // 构建RIP v1 响应数据包
+    public static byte[] createRipV1ResponsePacket() {
+        ByteArrayOutputStream bos = new ByteArrayOutputStream();
+        DataOutputStream dos = new DataOutputStream(bos);
+
+        try {
+            // 1. Command (8比特) - 响应报文 (Response)
+            dos.writeByte(2); // Command = 2，表示响应报文
+
+            // 2. Version (8比特) - RIP版本号 (RIP-1)
+            dos.writeByte(1); // Version = 1，RIP-1
+
+            // 3. Must be zero (16比特) - 保留字段，必须为零
+            dos.writeShort(0); // 16比特的保留字段，填充0
+
+            // 4. AFI (Address Family Identifier) (16比特) - 地址族标识符
+            dos.writeShort(2); // AFI = 2，表示 IPv4 地址
+
+            dos.writeShort(0);
+
+            InetAddress byName = InetAddress.getByName("200.0.2.0");
+            // 5. IP Address (32比特) - 路由目标 IP 地址
+            dos.write(byName.getAddress()); // 192.168.0.1 的 IP 地址（32位）
+
+            dos.writeInt(0);
+            dos.writeInt(0);
+            // 6. Metric (32比特) - 路由开销
+            dos.writeInt(1); // Metric = 1，表示一个跳数
+
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+
+        return bos.toByteArray();
+    }
+}