我们正在尝试在 Java 上编写 GPS 设备侦听器。
这样做时，我们无法为 CRC-ITU 错误检查开发正确的代码。从协议文档生成 crc 码的解释如下
终端或服务器可以使用校验码来区分接收到的信息是否有误。为防止数据传输过程中发生错误，在数据误操作的基础上增加了错误校验，提高了系统的安全性和效率。校验码由CRC-ITU校验方法生成。协议结构中数据的校验码，从数据包长度到信息序列号（包括“数据包长度”和“信息序列号”）都是CRC-ITU的值。如果在计算接收到的信息时出现CRC错误，接收方将忽略并丢弃该数据包。
这是数据监听器类
byte[] data = new byte[20];
System.out.println("Waiting for client on port " + serverSocket.getLocalPort() + "...");
Socket server = serverSocket.accept();
System.out.println("Just connected to " + server.getRemoteSocketAddress());
DataInputStream in = new DataInputStream(server.getInputStream());
System.out.println("in = " + in);
int packetSize = in.read(data, 0, data.length);
StringBuilder sb1 = new StringBuilder();
for (byte b : data) {
sb1.append(String.format("%02X ", b));
}
System.out.println("loginpacketHex = " + sb1.toString());
for (byte b : data) {
System.out.println("loginpacketinbytes = " + b);
}
NewClass cl = new NewClass();
byte[] t = new byte[4];
byte[] f = new byte[10];
t[0] = 0x05;
t[1] = data[3];
System.out.println(" t[1] = " + t[1]);
t[2] = data[data[2] - 6 + 5];
System.out.println("t[2] = " + t[2]);
t[3] = data[data[2] - 5 + 5];
System.out.println("t[3] = " + t[3]);
cl.set(t);
short x = cl.get();
f[0] = 0x78;
f[1] = 0x78;
f[2] = 0x05;
f[3] = data[3];
f[4] = data[data[2] - 6 + 5];
f[5] = data[data[2] - 5 + 5];
f[6] = (byte) ((x >> 8) & 0xff);
f[7] = (byte) (x & 0xff);
f[8] = 0x0d;
f[9] = 0x0a;
这是CRC生成类
public class NewClass {
public static int crc;
public static int[] table = {
0x0000, 0x1189, 0x2312, 0x329B, 0x4624, 0x57AD, 0x6536, 0x74BF,
0x8C48, 0x9DC1, 0xAF5A, 0xBED3, 0xCA6C, 0xDBE5, 0xE97E, 0xF8F7,
0x1081, 0x0108, 0x3393, 0x221A, 0x56A5, 0x472C, 0x75B7, 0x643E,
0x9CC9, 0x8D40, 0xBFDB, 0xAE52, 0xDAED, 0xCB64, 0xF9FF, 0xE876,
0x2102, 0x308B, 0x0210, 0x1399, 0x6726, 0x76AF, 0x4434, 0x55BD,
0xAD4A, 0xBCC3, 0x8E58, 0x9FD1, 0xEB6E, 0xFAE7, 0xC87C, 0xD9F5,
0x3183, 0x200A, 0x1291, 0x0318, 0x77A7, 0x662E, 0x54B5, 0x453C,
0xBDCB, 0xAC42, 0x9ED9, 0x8F50, 0xFBEF, 0xEA66, 0xD8FD, 0xC974,
0x4204, 0x538D, 0x6116, 0x709F, 0x0420, 0x15A9, 0x2732, 0x36BB,
0xCE4C, 0xDFC5, 0xED5E, 0xFCD7, 0x8868, 0x99E1, 0xAB7A, 0xBAF3,
0x5285, 0x430C, 0x7197, 0x601E, 0x14A1, 0x0528, 0x37B3, 0x263A,
0xDECD, 0xCF44, 0xFDDF, 0xEC56, 0x98E9, 0x8960, 0xBBFB, 0xAA72,
0x6306, 0x728F, 0x4014, 0x519D, 0x2522, 0x34AB, 0x0630, 0x17B9,
0xEF4E, 0xFEC7, 0xCC5C, 0xDDD5, 0xA96A, 0xB8E3, 0x8A78, 0x9BF1,
0x7387, 0x620E, 0x5095, 0x411C, 0x35A3, 0x242A, 0x16B1, 0x0738,
0xFFCF, 0xEE46, 0xDCDD, 0xCD54, 0xB9EB, 0xA862, 0x9AF9, 0x8B70,
0x8408, 0x9581, 0xA71A, 0xB693, 0xC22C, 0xD3A5, 0xE13E, 0xF0B7,
0x0840, 0x19C9, 0x2B52, 0x3ADB, 0x4E64, 0x5FED, 0x6D76, 0x7CFF,
0x9489, 0x8500, 0xB79B, 0xA612, 0xD2AD, 0xC324, 0xF1BF, 0xE036,
0x18C1, 0x0948, 0x3BD3, 0x2A5A, 0x5EE5, 0x4F6C, 0x7DF7, 0x6C7E,
0xA50A, 0xB483, 0x8618, 0x9791, 0xE32E, 0xF2A7, 0xC03C, 0xD1B5,
0x2942, 0x38CB, 0x0A50, 0x1BD9, 0x6F66, 0x7EEF, 0x4C74, 0x5DFD,
0xB58B, 0xA402, 0x9699, 0x8710, 0xF3AF, 0xE226, 0xD0BD, 0xC134,
0x39C3, 0x284A, 0x1AD1, 0x0B58, 0x7FE7, 0x6E6E, 0x5CF5, 0x4D7C,
0xC60C, 0xD785, 0xE51E, 0xF497, 0x8028, 0x91A1, 0xA33A, 0xB2B3,
0x4A44, 0x5BCD, 0x6956, 0x78DF, 0x0C60, 0x1DE9, 0x2F72, 0x3EFB,
0xD68D, 0xC704, 0xF59F, 0xE416, 0x90A9, 0x8120, 0xB3BB, 0xA232,
0x5AC5, 0x4B4C, 0x79D7, 0x685E, 0x1CE1, 0x0D68, 0x3FF3, 0x2E7A,
0xE70E, 0xF687, 0xC41C, 0xD595, 0xA12A, 0xB0A3, 0x8238, 0x93B1,
0x6B46, 0x7ACF, 0x4854, 0x59DD, 0x2D62, 0x3CEB, 0x0E70, 0x1FF9,
0xF78F, 0xE606, 0xD49D, 0xC514, 0xB1AB, 0xA022, 0x92B9, 0x8330,
0x7BC7, 0x6A4E, 0x58D5, 0x495C, 0x3DE3, 0x2C6A, 0x1EF1, 0x0F78,};
public short get() {
short c;
int y;
y = ~crc;
c = (short) y;
return c;
}
public void set(byte[] bytes) {
crc = 0xffff;
for (byte b : bytes) {
crc = (crc >>> 8) ^ table[(crc ^ b) & 0xff];
}
}
}
Incoming data string comes in following format
Example of data packet sent by the terminal 78 78 0D 01 01 23 45 67 89 01 23 45 00 01 8C DD 0D 0A
Explanation
Start Bit - 0x78 0x78
Length - 0x0D
Protocol - 0x01
Terminal ID - 0x01 0x23 0x45 0x67 0x89 0x01 0x23 0x45
Serial No - 0x00 0x01
Error - 0x8C 0xDD
Stop Bit - 0x0D 0x0A
我正在做这个更新的代码。
ByteArrayOutputStream bytearrypacket = new ByteArrayOutputStream();
DataOutputStream responce = new DataOutputStream(bytearrypacket);
responce.writeByte(0x0D);
responce.writeByte(1);
responce.writeByte(0x03);
responce.writeByte(0x53);
responce.writeByte(0x49);
responce.writeByte(0x20);
responce.writeByte(0x49);
responce.writeByte(0x00);
responce.writeByte(0x05);
responce.writeByte(0x34);
responce.writeShort(2);
NewClass cl = new NewClass();
cl.set(bytearrypacket.toByteArray());
System.out.println("cl = " + cl.get());
System.out.println("hexhexhex = " + Integer.toHexString(cl.get()));
responce.writeShort(cl.get());
byte[] res = bytearrypacket.toByteArray();
for (byte b : res) {
System.out.println("b = " + b);
}