tftp socket c++

TFTP是一个简单的文件传输协议，它使用UDP协议进行数据传输。在C++中，可以使用socket库来实现TFTP客户端和服务器端的开发。具体实现可以参考以下步骤：

1. 创建UDP socket
2. 构造TFTP请求报文
3. 发送TFTP请求报文到服务器
4. 接收服务器返回的TFTP数据包
. 解析TFTP数据包，获取文件内容
6. 关闭socket

以下是一个简单的TFTP客户端实现代码：

#include <iostream>
#include <cstring>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

using namespace std;

#define TFTP_SERVER_IP "127.0.0.1"
#define TFTP_SERVER_PORT 69

#define TFTP_OPCODE_RRQ 1
#define TFTP_OPCODE_DATA 3
#define TFTP_OPCODE_ACK 4
#define TFTP_OPCODE_ERROR 5

struct tftp_packet {
    uint16_t opcode;
    union {
        struct {
            char filename[128];
            char mode[16];
        } rrq;
        struct {
            uint16_t block_num;
            char data[512];
        } data;
        struct {
            uint16_t block_num;
        } ack;
        struct {
            uint16_t error_code;
            char error_msg[128];
        } error;
    } data;
};

int main() {
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        cerr << "Failed to create socket" << endl;
        return -1;
    }

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(TFTP_SERVER_PORT);
    server_addr.sin_addr.s_addr = inet_addr(TFTP_SERVER_IP);

    struct tftp_packet rrq_packet;
    memset(&rrq_packet, 0, sizeof(rrq_packet));
    rrq_packet.opcode = htons(TFTP_OPCODE_RRQ);
    strcpy(rrq_packet.data.rrq.filename, "test.txt");
    strcpy(rrq_packet.data.rrq.mode, "octet");

    if (sendto(sockfd, &rrq_packet, sizeof(rrq_packet), 0, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
        cerr << "Failed to send RRQ packet" << endl;
        close(sockfd);
        return -1;
    }

    struct tftp_packet recv_packet;
    memset(&recv_packet, 0, sizeof(recv_packet));
    socklen_t server_addr_len = sizeof(server_addr);
    while (true) {
        if (recvfrom(sockfd, &recv_packet, sizeof(recv_packet), 0, (struct sockaddr*)&server_addr, &server_addr_len) < 0) {
            cerr << "Failed to receive packet" << endl;
            close(sockfd);
            return -1;
        }

        if (ntohs(recv_packet.opcode) == TFTP_OPCODE_DATA) {
            uint16_t block_num = ntohs(recv_packet.data.data.block_num);
            cout << "Received data block " << block_num << endl;

            // TODO: 处理数据包中的文件内容

            struct tftp_packet ack_packet;
            memset(&ack_packet, 0, sizeof(ack_packet));
            ack_packet.opcode = htons(TFTP_OPCODE_ACK);
            ack_packet.data.ack.block_num = htons(block_num);

            if (sendto(sockfd, &ack_packet, sizeof(ack_packet), 0, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {
                cerr << "Failed to send ACK packet" << endl;
                close(sockfd);
                return -1;
            }
        } else if (ntohs(recv_packet.opcode) == TFTP_OPCODE_ERROR) {
            uint16_t error_code = ntohs(recv_packet.data.error.error_code);
            char* error_msg = recv_packet.data.error.error_msg;
            cerr << "Received error packet: " << error_code << " " << error_msg << endl;
            close(sockfd);
            return -1;
        } else {
            cerr << "Received unexpected packet" << endl;
            close(sockfd);
            return -1;
        }
    }

    close(sockfd);
    return 0;
}