使用java实现Xmodem协议
发布时间:2020-12-14 14:35:55 所属栏目:Java 来源:网络整理
导读:1.介绍 Xmodem是一种在串口通信中广泛使用的异步文件传输协议,分为Xmodem(使用128字节的数据块)和1k-Xmodem(使用1024字节即1k字节的数据块)协议两种。 本文实现的是128字节数据块的Xmodem协议,采用CRC16校验,在项目中应用时,发送端和接收端可根据具
1.介绍 Xmodem是一种在串口通信中广泛使用的异步文件传输协议,分为Xmodem(使用128字节的数据块)和1k-Xmodem(使用1024字节即1k字节的数据块)协议两种。 2.实现 在和嵌入式同学调试的过程中,发现发送端发送数据过快,导致接收端处理不过来,所以在send方法中开启了一个子线程来处理数据发送逻辑,方便加入延时处理。 public class Xmodem { // 开始 private final byte SOH = 0x01; // 结束 private final byte EOT = 0x04; // 应答 private final byte ACK = 0x06; // 重传 private final byte NAK = 0x15; // 无条件结束 private final byte CAN = 0x18; // 以128字节块的形式传输数据 private final int SECTOR_SIZE = 128; // 最大错误(无应答)包数 private final int MAX_ERRORS = 10; // 输入流,用于读取串口数据 private InputStream inputStream; // 输出流,用于发送串口数据 private OutputStream outputStream; public Xmodem(InputStream inputStream,OutputStream outputStream) { this.inputStream = inputStream; this.outputStream = outputStream; } /** * 发送数据 * * @param filePath * 文件路径 */ public void send(final String filePath) { new Thread() { public void run() { try { // 错误包数 int errorCount; // 包序号 byte blockNumber = 0x01; // 校验和 int checkSum; // 读取到缓冲区的字节数量 int nbytes; // 初始化数据缓冲区 byte[] sector = new byte[SECTOR_SIZE]; // 读取文件初始化 DataInputStream inputStream = new DataInputStream( new FileInputStream(filePath)); while ((nbytes = inputStream.read(sector)) > 0) { // 如果最后一包数据小于128个字节,以0xff补齐 if (nbytes < SECTOR_SIZE) { for (int i = nbytes; i < SECTOR_SIZE; i++) { sector[i] = (byte) 0xff; } } // 同一包数据最多发送10次 errorCount = 0; while (errorCount < MAX_ERRORS) { // 组包 // 控制字符 + 包序号 + 包序号的反码 + 数据 + 校验和 putData(SOH); putData(blockNumber); putData(~blockNumber); checkSum = CRC16.calc(sector) & 0x00ffff; putChar(sector,(short) checkSum); outputStream.flush(); // 获取应答数据 byte data = getData(); // 如果收到应答数据则跳出循环,发送下一包数据 // 未收到应答,错误包数+1,继续重发 if (data == ACK) { break; } else { ++errorCount; } } // 包序号自增 blockNumber = (byte) ((++blockNumber) % 256); } // 所有数据发送完成后,发送结束标识 boolean isAck = false; while (!isAck) { putData(EOT); isAck = getData() == ACK; } } catch (Exception e) { e.printStackTrace(); } }; }.start(); } /** * 接收数据 * * @param filePath * 文件路径 * @return 是否接收完成 * @throws IOException * 异常 */ public boolean receive(String filePath) throws Exception { // 错误包数 int errorCount = 0; // 包序号 byte blocknumber = 0x01; // 数据 byte data; // 校验和 int checkSum; // 初始化数据缓冲区 byte[] sector = new byte[SECTOR_SIZE]; // 写入文件初始化 DataOutputStream outputStream = new DataOutputStream( new FileOutputStream(filePath)); // 发送字符C,CRC方式校验 putData((byte) 0x43); while (true) { if (errorCount > MAX_ERRORS) { outputStream.close(); return false; } // 获取应答数据 data = getData(); if (data != EOT) { try { // 判断接收到的是否是开始标识 if (data != SOH) { errorCount++; continue; } // 获取包序号 data = getData(); // 判断包序号是否正确 if (data != blocknumber) { errorCount++; continue; } // 获取包序号的反码 byte _blocknumber = (byte) ~getData(); // 判断包序号的反码是否正确 if (data != _blocknumber) { errorCount++; continue; } // 获取数据 for (int i = 0; i < SECTOR_SIZE; i++) { sector[i] = getData(); } // 获取校验和 checkSum = (getData() & 0xff) << 8; checkSum |= (getData() & 0xff); // 判断校验和是否正确 int crc = CRC16.calc(sector); if (crc != checkSum) { errorCount++; continue; } // 发送应答 putData(ACK); // 包序号自增 blocknumber++; // 将数据写入本地 outputStream.write(sector); // 错误包数归零 errorCount = 0; } catch (Exception e) { e.printStackTrace(); } finally { // 如果出错发送重传标识 if (errorCount != 0) { putData(NAK); } } } else { break; } } // 关闭输出流 outputStream.close(); // 发送应答 putData(ACK); return true; } /** * 获取数据 * * @return 数据 * @throws IOException * 异常 */ private byte getData() throws IOException { return (byte) inputStream.read(); } /** * 发送数据 * * @param data * 数据 * @throws IOException * 异常 */ private void putData(int data) throws IOException { outputStream.write((byte) data); } /** * 发送数据 * * @param data * 数据 * @param checkSum * 校验和 * @throws IOException * 异常 */ private void putChar(byte[] data,short checkSum) throws IOException { ByteBuffer bb = ByteBuffer.allocate(data.length + 2).order( ByteOrder.BIG_ENDIAN); bb.put(data); bb.putShort(checkSum); outputStream.write(bb.array()); } } CRC16校验算法,采用的是查表法。 public class CRC16 { private static final char crctable[] = { 0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7,0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef,0x1231,0x0210,0x3273,0x2252,0x52b5,0x4294,0x72f7,0x62d6,0x9339,0x8318,0xb37b,0xa35a,0xd3bd,0xc39c,0xf3ff,0xe3de,0x2462,0x3443,0x0420,0x1401,0x64e6,0x74c7,0x44a4,0x5485,0xa56a,0xb54b,0x8528,0x9509,0xe5ee,0xf5cf,0xc5ac,0xd58d,0x3653,0x2672,0x1611,0x0630,0x76d7,0x66f6,0x5695,0x46b4,0xb75b,0xa77a,0x9719,0x8738,0xf7df,0xe7fe,0xd79d,0xc7bc,0x48c4,0x58e5,0x6886,0x78a7,0x0840,0x1861,0x2802,0x3823,0xc9cc,0xd9ed,0xe98e,0xf9af,0x8948,0x9969,0xa90a,0xb92b,0x5af5,0x4ad4,0x7ab7,0x6a96,0x1a71,0x0a50,0x3a33,0x2a12,0xdbfd,0xcbdc,0xfbbf,0xeb9e,0x9b79,0x8b58,0xbb3b,0xab1a,0x6ca6,0x7c87,0x4ce4,0x5cc5,0x2c22,0x3c03,0x0c60,0x1c41,0xedae,0xfd8f,0xcdec,0xddcd,0xad2a,0xbd0b,0x8d68,0x9d49,0x7e97,0x6eb6,0x5ed5,0x4ef4,0x3e13,0x2e32,0x1e51,0x0e70,0xff9f,0xefbe,0xdfdd,0xcffc,0xbf1b,0xaf3a,0x9f59,0x8f78,0x9188,0x81a9,0xb1ca,0xa1eb,0xd10c,0xc12d,0xf14e,0xe16f,0x1080,0x00a1,0x30c2,0x20e3,0x5004,0x4025,0x7046,0x6067,0x83b9,0x9398,0xa3fb,0xb3da,0xc33d,0xd31c,0xe37f,0xf35e,0x02b1,0x1290,0x22f3,0x32d2,0x4235,0x5214,0x6277,0x7256,0xb5ea,0xa5cb,0x95a8,0x8589,0xf56e,0xe54f,0xd52c,0xc50d,0x34e2,0x24c3,0x14a0,0x0481,0x7466,0x6447,0x5424,0x4405,0xa7db,0xb7fa,0x8799,0x97b8,0xe75f,0xf77e,0xc71d,0xd73c,0x26d3,0x36f2,0x0691,0x16b0,0x6657,0x7676,0x4615,0x5634,0xd94c,0xc96d,0xf90e,0xe92f,0x99c8,0x89e9,0xb98a,0xa9ab,0x5844,0x4865,0x7806,0x6827,0x18c0,0x08e1,0x3882,0x28a3,0xcb7d,0xdb5c,0xeb3f,0xfb1e,0x8bf9,0x9bd8,0xabbb,0xbb9a,0x4a75,0x5a54,0x6a37,0x7a16,0x0af1,0x1ad0,0x2ab3,0x3a92,0xfd2e,0xed0f,0xdd6c,0xcd4d,0xbdaa,0xad8b,0x9de8,0x8dc9,0x7c26,0x6c07,0x5c64,0x4c45,0x3ca2,0x2c83,0x1ce0,0x0cc1,0xef1f,0xff3e,0xcf5d,0xdf7c,0xaf9b,0xbfba,0x8fd9,0x9ff8,0x6e17,0x7e36,0x4e55,0x5e74,0x2e93,0x3eb2,0x0ed1,0x1ef0 }; public static char calc(byte[] bytes) { char crc = 0x0000; for (byte b : bytes) { crc = (char) ((crc << 8) ^ crctable[((crc >> 8) ^ b) & 0x00ff]); } return (char) (crc); } } 3.使用 // serialPort为串口对象 Xmodem xmodem = new Xmodem(serialPort.getInputStream(),serialPort.getOutputStream()); // filePath为文件路径 // ./bin/xxx.bin xmodem.send(filePath); 4.写在最后 完整的代码下载 以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持编程小技巧。 (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |