从0到1用java再造tcpip协议栈：代码实现ping应用功能1

package protocol;import java.util.HashMap;public interface IProtocol {
   public byte[] createHeader(HashMap<String, byte[]> headerInfo);
}package protocol;public class ProtocolManager {
   private static ProtocolManager instance = null;
   private ProtocolManager() {}
   public static ProtocolManager getInstance() {
       if (instance == null) {
           instance = new ProtocolManager();
       }       return instance;
   }   public IProtocol getProtocol(String name) {
       switch (name.toLowerCase()) {
       case "icmp":
           return new ICMPProtocolLayer();
       case "ip":
           return new IPProtocolLayer();
       }       return null;
   }
}

package protocol;import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.Random;import utils.Utility;public class ICMPEchoHeader implements IProtocol{
   private static int ICMP_EOCH_HEADER_LENGTH = 16;
   private static short ICMP_ECHO_TYPE = 8;
   private static short ICMP_ECHO_REPLY_TYPE = 0;   @Override
   public byte[] createHeader(HashMap<String, Object> headerInfo) {
       String headerName = (String)headerInfo.get("header");
       if (headerName != "echo" && headerName != "echo_reply") {
           return null;
       }       byte[] buffer = new byte[ICMP_EOCH_HEADER_LENGTH];
       ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);       short type = ICMP_ECHO_TYPE;
       if (headerName == "echo_reply") {
           type = ICMP_ECHO_REPLY_TYPE;
       }
       byteBuffer.putShort(type);
       short code = 0;
       byteBuffer.putShort(code);       short checkSum = 0;
       byteBuffer.putShort(checkSum);       short identifier = 0;
       if (headerInfo.get("identifier") == null) {
           Random ran = new Random();
           identifier = (short) ran.nextInt();
           headerInfo.put("identifier", identifier);
       }
       identifier = (short) headerInfo.get("identifier");
       byteBuffer.putShort(identifier);       short sequenceNumber = 0;
       if (headerInfo.get("sequence_number") != null) {
           sequenceNumber = (short) headerInfo.get("sequence_number");
           sequenceNumber += 1;
       }
       headerInfo.put("sequence_number", sequenceNumber);
       byteBuffer.putShort(sequenceNumber);       checkSum = (short) Utility.checksum(byteBuffer.array(), byteBuffer.array().length);
       byteBuffer.putShort(4, checkSum);               return byteBuffer.array();
   }}

public class ICMPProtocolLayer implements PacketReceiver, IProtocol{
....
private ArrayList<IProtocol> protocol_header_list = new ArrayList<IProtocol>();
public ICMPProtocolLayer() {
       //添加错误消息处理对象
       error_handler_list.add(new ICMPUnReachableMsgHandler());
       //增加icmp echo 协议包头创建对象
       protocol_header_list.add(new ICMPEchoHeader());
   }
....
 public byte[] createHeader(HashMap<String, Object> headerInfo) {
       for (int i = 0; i < protocol_header_list.size(); i++) {
           byte[] buff = protocol_header_list.get(i).createHeader(headerInfo);
           if (buff != null) {
               return buff;
           }
       }       return null;
   }
}

package protocol;import java.nio.ByteBuffer;
import java.util.HashMap;import utils.Utility;public class IPProtocolLayer implements IProtocol{
   private static byte IP_VERSION = 4;
   private static int CHECKSUM_OFFSET = 10;   @Override
   public byte[] createHeader(HashMap<String, Object> headerInfo) {
       byte version = IP_VERSION;
       byte internetHeaderLength = 5;
       if (headerInfo.get("internet_header_length") != null) {
           internetHeaderLength = (byte)headerInfo.get("internet_header_length");
       }
       byte[] buffer = new byte[internetHeaderLength];
       ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
       byteBuffer.put((byte) (internetHeaderLength << 4 | version));       byte dscp = 0;
       if (headerInfo.get("dscp") != null) {
           dscp = (byte)headerInfo.get("dscp");
       }
       byte ecn = 0;
       if (headerInfo.get("ecn") != null) {
           ecn = (byte)headerInfo.get("ecn");
       }
       byteBuffer.put((byte)(dscp | ecn << 6));       if (headerInfo.get("total_length") == null) {
           return null;
       }       short totalLength = (short)headerInfo.get("total_length");
       byteBuffer.putShort(totalLength);       int identification = 0;
       if (headerInfo.get("identification") != null) {
           identification = (int)headerInfo.get("identification");
       }
       byteBuffer.putInt(identification);       short flagAndOffset = 0;
       if (headerInfo.get("flag") != null) {
           flagAndOffset = (short)headerInfo.get("flag");
       }
       if (headerInfo.get("fragment_offset") != null) {
           flagAndOffset |= ((short)headerInfo.get("fragment_offset")) << 3;
       }
       byteBuffer.putShort(flagAndOffset);       short timeToLive = 64;
       if (headerInfo.get("time_to_live") != null) {
           timeToLive = (short)headerInfo.get("time_to_live");
       }
       byteBuffer.putShort(timeToLive);       short protocol = 0;
       if (headerInfo.get("protocol") == null) {
           return null;
       }
       protocol = (short)headerInfo.get("protocol");
       byteBuffer.putShort(protocol);       short checkSum = 0;
       byteBuffer.putShort(checkSum);       int srcIP = 0;
       if (headerInfo.get("source_ip") == null) {
           return null;
       }
       srcIP = (int)headerInfo.get("source_ip");
       byteBuffer.putInt(srcIP);       int destIP = 0;
       if (headerInfo.get("destination_ip") == null) {
           return null;
       }
       byteBuffer.putInt(destIP);       if (headerInfo.get("options") != null) {
           byte[] options = (byte[])headerInfo.get("options");
           byteBuffer.put(options);
       }       checkSum = (short) Utility.checksum(byteBuffer.array(), byteBuffer.array().length);
       byteBuffer.putShort(CHECKSUM_OFFSET, checkSum);       return byteBuffer.array();
   }}

package Application;public interface IApplication {
   public  int getPort();
   public boolean isClosed();
   public  void handleData(byte[] data);
}package Application;public interface IApplicationManager {
   public  IApplication getApplicationByPort(int port);
}package Application;import java.util.ArrayList;public class ApplicationManager implements IApplicationManager{
   private ArrayList<IApplication> application_list = new ArrayList<IApplication>();   @Override
   public IApplication getApplicationByPort(int port) {
       for (int i = 0; i < application_list.size(); i++) {
           IApplication app = application_list.get(i);
           if (app.getPort() == port) {
               return app;
           }
       }       return null;
   }}