Ymodem接收和发送C程序

以下是Ymodem协议的发送和接收C代码示例。

Ymodem发送代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <termios.h>

#define PACKET_SIZE 1024

int send_ymodem_packet(int fd, unsigned char *packet, int packet_size) {
    unsigned char data[PACKET_SIZE + 6];
    int i, j;
    int crc = 0;
    int count = 0;

    data[0] = SOH; // start of header
    data[1] = count & 0xFF;
    data[2] = (~count) & 0xFF;

    memcpy(&data[3], packet, packet_size);

    for (i = 0; i < packet_size + 3; i++) {
        crc += data[i+3];
    }

    data[packet_size+3] = crc & 0xFF;
    data[packet_size+4] = (crc >> 8) & 0xFF;
    data[packet_size+5] = EOT; // end of transmission

    for (i = 0; i < 10; i++) {
        write(fd, &data, packet_size + 6);
        usleep(100000); // wait for receiver
        j = read(fd, &data, 1);
        if (j == 1 && data[0] == ACK) {
            return 0;
        }
    }

    return -1;
}

int send_ymodem(int fd, const char *filename) {
    struct stat st;
    unsigned char packet[PACKET_SIZE];
    int i, j, ret;

    int file = open(filename, O_RDONLY);
    if (file < 0) {
        printf("Failed to open %s\n", filename);
        return -1;
    }

    fstat(file, &st);

    int packet_count = (st.st_size + PACKET_SIZE - 1) / PACKET_SIZE;

    // send file information
    unsigned char data[PACKET_SIZE + 6];
    memset(data, 0, PACKET_SIZE + 6);
    data[0] = STX; // start of text
    data[1] = 0x00; // block number
    data[2] = (~0x00) & 0xFF; // complement of block number
    strncpy((char *)&data[3], filename, PACKET_SIZE - 4);
    int len = strlen(filename);
    data[3 + len] = 0x00;
    sprintf((char *)&data[4 + len], "%d", st.st_size);
    len = strlen((char *)&data[4 + len]);
    data[4 + len + 1] = 0x00;
    send_ymodem_packet(fd, data, PACKET_SIZE);

    // send file contents
    for (i = 0; i < packet_count; i++) {
        memset(packet, 0, PACKET_SIZE);
        read(file, packet, PACKET_SIZE);
        ret = send_ymodem_packet(fd, packet, PACKET_SIZE);
        if (ret < 0) {
            printf("Failed to send packet\n");
            return -1;
        }
    }

    // send end of transmission
    unsigned char eot = EOT;
    for (i = 0; i < 10; i++) {
        write(fd, &eot, 1);
        usleep(100000); // wait for receiver
        j = read(fd, &eot, 1);
        if (j == 1 && eot == ACK) {
            return 0;
        }
    }

    return -1;
}

Ymodem接收代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <termios.h>

#define PACKET_SIZE 1024

int receive_ymodem_packet(int fd, unsigned char *packet) {
    unsigned char data[PACKET_SIZE + 6];
    int i, j;
    int crc = 0;
    int count = 0;

    for (i = 0; i < 10; i++) {
        j = read(fd, &data, PACKET_SIZE + 6);
        if (j == PACKET_SIZE + 6 && data[0] == SOH) {
            count = data[1];
            crc = data[packet_size+3] | (data[packet_size+4] << 8);
            for (i = 0; i < packet_size + 3; i++) {
                crc += data[i+3];
            }
            if ((crc & 0xFFFF) == 0) {
                memcpy(packet, &data[3], PACKET_SIZE);
                return PACKET_SIZE;
            }
        }
        else if (j == 1 && data[0] == EOT) {
            write(fd, &ACK, 1);
            return 0;
        }
        else if (j == 1 && data[0] == CAN) {
            return -1;
        }
    }

    return -1;
}

int receive_ymodem(int fd, const char *filename) {
    unsigned char packet[PACKET_SIZE];
    int i, j, ret;

    int file = open(filename, O_CREAT | O_WRONLY, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH);
    if (file < 0) {
        printf("Failed to create %s\n", filename);
        return -1;
    }

    // receive file information
    unsigned char data[PACKET_SIZE + 6];
    memset(data, 0, PACKET_SIZE + 6);
    int num = 0;
    for (i = 0; i < 10; i++) {
        write(fd, &C, 1);
        usleep(100000);
        j = read(fd, &data, PACKET_SIZE + 6);
        if (j == PACKET_SIZE + 6 && data[0] == STX) {
            if (data[1] == num && (~data[1]) == data[2]) {
                strncpy(filename, (char *)&data[3], PACKET_SIZE - 4);
                int len = strlen(filename);
                int size = atoi((char *)&data[4 + len + 1]);
                write(fd, &ACK, 1);
                return size;
            }
        }
        else if (j == 1 && data[0] == EOT) {
            write(fd, &ACK, 1);
            return 0;
        }
        else if (j == 1 && data[0] == CAN) {
            return -1;
        }
    }

    // receive file contents
    int size = 0;
    while (1) {
        memset(packet, 0, PACKET_SIZE);
        ret = receive_ymodem_packet(fd, packet);
        if (ret == PACKET_SIZE) {
            write(file, packet, PACKET_SIZE);
            size += PACKET_SIZE;
        }
        else if (ret == 0) {
            write(fd, &ACK, 1);
            return size;
        }
        else if (ret < 0) {
            write(fd, &NAK, 1);
        }
    }

    return -1;
}

以上代码是基于Linux系统的串口通信实现的Ymodem协议发送和接收程序。需要注意的是，这里使用的串口通信库可能会因系统环境的不同而有所不同，需要根据实际情况进行修改。