c语言tftp服务器编程代码

以下是一个简单的C语言TFTP服务器编程代码示例。该代码实现了基本的TFTP协议功能，包括读取和写入文件的能力。请注意，这是一个基础示例，可能需要根据具体需求进行优化和错误处理。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define TFTP_PORT 69
#define MAX_DATA_SIZE 512
#define BLOCK_SIZE 512
#define TIMEOUT 5

enum Opcode {
    OP_RRQ = 1,
    OP_WRQ = 2,
    OP_DATA = 3,
    OP_ACK = 4,
    OP_ERROR = 5
};

struct tftp_packet {
    uint16_t opcode;
    char data[MAX_DATA_SIZE];
};

void handle_rrq(int sockfd, struct sockaddr_in client_addr, socklen_t addr_len, char *filename, char *mode);
void handle_wrq(int sockfd, struct sockaddr_in client_addr, socklen_t addr_len, char *filename, char *mode);

int main() {
    int sockfd;
    struct sockaddr_in server_addr, client_addr;
    socklen_t addr_len = sizeof(client_addr);
    char buffer[BLOCK_SIZE];

    // Create UDP socket
    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
        perror("Socket creation failed");
        exit(EXIT_FAILURE);
    }

    // Bind the socket to the port
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = INADDR_ANY;
    server_addr.sin_port = htons(TFTP_PORT);

    if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("Bind failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    printf("TFTP server started on port %d\n", TFTP_PORT);

    while (1) {
        ssize_t bytes_received = recvfrom(sockfd, buffer, BLOCK_SIZE, 0, (struct sockaddr *)&client_addr, &addr_len);
        if (bytes_received < 0) {
            perror("Receive failed");
            continue;
        }

        struct tftp_packet *packet = (struct tftp_packet *)buffer;

        switch (ntohs(packet->opcode)) {
            case OP_RRQ:
                handle_rrq(sockfd, client_addr, addr_len, packet->data, packet->data + strlen(packet->data) + 1);
                break;
            case OP_WRQ:
                handle_wrq(sockfd, client_addr, addr_len, packet->data, packet->data + strlen(packet->data) + 1);
                break;
            default:
                printf("Unknown opcode: %d\n", ntohs(packet->opcode));
                break;
        }
    }

    close(sockfd);
    return 0;
}

void handle_rrq(int sockfd, struct sockaddr_in client_addr, socklen_t addr_len, char *filename, char *mode) {
    FILE *file;
    char buffer[BLOCK_SIZE];
    uint16_t block_num = 1;
    ssize_t bytes_read;

    if ((file = fopen(filename, "rb")) == NULL) {
        printf("File not found: %s\n", filename);
        // Send error packet
        struct tftp_packet error_packet;
        error_packet.opcode = htons(OP_ERROR);
        error_packet.data[0] = 1; // File not found error code
        strcpy(error_packet.data + 2, "File not found");
        sendto(sockfd, &error_packet, 5 + strlen("File not found"), 0, (struct sockaddr *)&client_addr, addr_len);
        return;
    }

    while ((bytes_read = fread(buffer + 2, 1, BLOCK_SIZE - 2, file)) > 0) {
        struct tftp_packet data_packet;
        data_packet.opcode = htons(OP_DATA);
        data_packet.data[0] = (block_num >> 8) & 0xFF;
        data_packet.data[1] = block_num & 0xFF;
        memcpy(data_packet.data + 2, buffer + 2, bytes_read);

        sendto(sockfd, &data_packet, bytes_read + 4, 0, (struct sockaddr *)&client_addr, addr_len);

        // Wait for ACK
        struct tftp_packet ack_packet;
        ssize_t bytes_received = recvfrom(sockfd, &ack_packet, BLOCK_SIZE, 0, (struct sockaddr *)&client_addr, &addr_len);
        if (bytes_received < 0 || ntohs(ack_packet.opcode) != OP_ACK || ntohs(*(uint16_t *)(ack_packet.data)) != block_num) {
            printf("ACK error for block %d\n", block_num);
            fseek(file, (block_num - 1) * (BLOCK_SIZE - 2), SEEK_SET);
            continue;
        }

        block_num++;
    }

    fclose(file);
    printf("File sent successfully: %s\n", filename);
}

void handle_wrq(int sockfd, struct sockaddr_in client_addr, socklen_t addr_len, char *filename, char *mode) {
    FILE *file;
    char buffer[BLOCK_SIZE];
    uint16_t block_num = 0;
    ssize_t bytes_received;

    if ((file = fopen(filename, "wb")) == NULL) {
        printf("Failed to open file for writing: %s\n", filename);
        // Send error packet
        struct tftp_packet error_packet;
        error_packet.opcode = htons(OP_ERROR);
        error_packet.data[0] = 3; // Disk full or allocation exceeded error code
        strcpy(error_packet.data + 2, "Disk full or allocation exceeded");
        sendto(sockfd, &error_packet, 5 + strlen("Disk full or allocation exceeded"), 0, (struct sockaddr *)&client_addr, addr_len);
        return;
    }

    while (1) {
        struct tftp_packet data_packet;
        bytes_received = recvfrom(sockfd, &data_packet, BLOCK_SIZE, 0, (struct sockaddr *)&client_addr, &addr_len);
        if (bytes_received < 0) {
            perror("Receive failed");
            continue;
        }

        if (ntohs(data_packet.opcode) != OP_DATA) {
            printf("Unexpected packet received\n");
            continue;
        }

        block_num = ntohs(*(uint16_t *)(data_packet.data));

        if (fwrite(data_packet.data + 2, 1, bytes_received - 4, file) < bytes_received - 4) {
            printf("Write error\n");
            break;
        }

        if (bytes_received < BLOCK_SIZE) {
            break;
        }

        // Send ACK
        struct tftp_packet ack_packet;
        ack_packet.opcode = htons(OP_ACK);
        ack_packet.data[0] = (block_num >> 8) & 0xFF;
        ack_packet.data[1] = block_num & 0xFF;
        sendto(sockfd, &ack_packet, 4, 0, (struct sockaddr *)&client_addr, addr_len);
    }

    fclose(file);
    printf("File received successfully: %s\n", filename);
}

### 代码说明

1. **主函数**:
- 创建一个UDP套接字并绑定到69端口。
- 进入无限循环，等待客户端请求。
- 根据收到的请求类型（RRQ或WRQ）调用相应的处理函数。

2. **handle_rrq**:
- 处理读文件请求（RRQ）。
- 打开文件，逐块读取数据并发送给客户端。
- 等待客户端的ACK确认，如果没有收到或收到错误的ACK，重新发送数据块。

3. **handle_wrq**:
- 处理写文件请求（WRQ）。
- 打开文件，逐块接收数据并写入文件。
- 发送ACK确认给客户端。

### 注意事项

- 该代码只是一个基础示例，实际应用中需要添加更多的错误处理和日志记录。
- TFTP协议有一些高级功能（如多线程、超时重传等）未在此示例中实现，可根据需要进行扩展。
- 该代码假设文件名和模式都是以NULL结尾的字符串，实际应用中需要确保这一点。