import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.InetAddress;import java.net.ServerSocket;import java.net.Socket;import java.net.UnknownHostException;/** * Created by SiKang on 2016/4/29. */public class CustomData { public static void main(String args[]) {  //服務端線程  new Thread(new Runnable() {   @Override   public void run() {    try {     //開啟服務端Socket     ServerSocket server = new ServerSocket(9000);     //等待客戶端連接     Socket socket = server.accept();     InputStream inputStream = socket.getInputStream();     //先得到前兩個字節 為報文長度     byte[] lenBytes = new byte[2];     inputStream.read(lenBytes);     short length = bytesToShort(lenBytes);   System.out.println("length: " + length);     //然后得到接下來的四個字節 crc32校驗碼     byte[] crc = new byte[4];     inputStream.read(crc);     int crc32 = bytesToInt(crc);     //得到剩下的字段 ver、cmd、data     byte[] bytes = new byte[length - 2 - 4];     inputStream.read(bytes);     //根據得到的bytes獲取新的Crc32校驗碼 驗證數據是否完整（可以在讀取bytes時少讀一位，看看能不能通過）     if (crc32 == getCRC32(bytes)) {      System.out.println("Crc32 Right!");     }else{   System.out.println("Crc32 Error!");      return;   }     //取出ver cmd     int ver = Integer.parseInt(byteToHex(bytes[0]), 16);     int cmd = Integer.parseInt(byteToHex(bytes[1]), 16);     //看看ver是否是客戶端發送0x05     if (ver == 0x05) {      System.out.println("ver: 0x05");     }     //cmd是否是客戶端發送0xff     if (cmd == 0xff) {      System.out.println("cmd: 0xff");     }     //得到剩下的數據字節數，取出data數據     int datalen = length - 2 - 4 - 1 - 1;     byte[] data = new byte[datalen];     int index = 1;     for (int i = 0; i < datalen; i++) {      data[i] = bytes[++index];     }     String str = new String(data);     System.out.println("data: " + str);     inputStream.close();    } catch (IOException e) {     e.printStackTrace();    }   }  }).start();  //客戶端線程  new Thread(new Runnable() {   @Override   public void run() {    try {     //連接服務端     Socket socket = new Socket(getIpAddress(), 9000);     OutputStream outputStream = socket.getOutputStream();     String str = "Hellow World!";     byte[] data = str.getBytes();     //發送報文     pack(outputStream, (byte) 0xff, data, data.length);     outputStream.flush();     outputStream.close();    } catch (IOException e) {     e.printStackTrace();    }   }  }).start(); } /** *封裝并發送報文 *這里報文格式為{報文總長度[2字節]，Crc32校驗碼[4字節]，ver版本信息[1字節]，cmd指令[1字節]，data數據內容[若干字節]} */ private static void pack(OutputStream out, byte cmd, byte[] data, int len) {  try {   //先得到報文總長度，如上介紹的格式 字節數相加   short totalSize = (short) (2 + 4 + 1 + 1 + len);   //輸出報文長度   out.write(shortToByte(totalSize), 0, 2);   //需要校驗的字段   byte[] bytes = new byte[1 + 1 + len];   int index = 0;   bytes[index++] = 0x05;//版本號（這里是寫死的）   bytes[index++] = cmd;//cmd指令   //數據內容   for (int i = 0; i < len; i++) {    bytes[index++] = data[i];   }   //得到ver、cmd、data的crc32校驗碼（Crc32算法在最下邊，網上找的.....）   byte[] crc32 = intToBytes(getCRC32(bytes));   //輸出crc校驗碼   out.write(crc32, 0, crc32.length);   //輸出ver、cmd、data   out.write(bytes, 0, bytes.length);  } catch (IOException e) {   e.printStackTrace();  } } /**  * 得到本機IP  */ private static String getIpAddress() throws UnknownHostException {  InetAddress address = InetAddress.getLocalHost();  return address.getHostAddress(); } /**  * int轉byte[]  */ public static byte[] intToBytes(int value) {  byte[] bytes = new byte[4];  bytes[3] = (byte) (value >> 24);  bytes[2] = (byte) (value >> 16);  bytes[1] = (byte) (value >> 8);  bytes[0] = (byte) (value >> 0);  return bytes; } /**  * short轉byte[]  */ public static byte[] shortToByte(short value) {  byte[] bytes = new byte[2];  bytes[1] = (byte) (value >> 8);  bytes[0] = (byte) (value >> 0);  return bytes; } /**  * byte轉16進制  */ public static String byteToHex(byte b) {  int i = b & 0xFF;  return Integer.toHexString(i); } /**  * byte[]轉int  */ public static int bytesToInt(byte[] bytes) {  return (int) ((((bytes[3] & 0xff) << 24)    | ((bytes[2] & 0xff) << 16)    | ((bytes[1] & 0xff) << 8) | ((bytes[0] & 0xff) << 0))); } /**  * byte[]轉short  */ public static short bytesToShort(byte[] bytes) {  return (short) (((bytes[1] << 8) | bytes[0] & 0xff)); } /**  * 得到CRC32校驗碼  */ public static int getCRC32(byte[] bytes) {  int[] table = {    0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,    0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,    0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,    0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,    0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,    0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,    0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,    0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,    0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,    0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,    0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,    0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,    0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,    0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,    0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,    0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,    0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,    0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,    0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,    0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,    0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,    0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,    0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,    0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,    0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,    0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,    0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,    0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,    0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,    0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,    0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,    0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,  };  int crc = 0xffffffff;  for (byte b : bytes) {   crc = (crc >>> 8 ^ table[(crc ^ b) & 0xff]);  }  crc = crc ^ 0xffffffff;  return crc; }}