tftp协议概述
简单文件传输协议，适用于在网络上进行文件传输的一套标准协议，使用UDP传输
特点：
是应用层协议
基于UDP协议实现
数据传输模式
octet：二进制模式（常用）
mail：已经不再支持
TFTP通信过程总结
- 服务器在69号端口等待客户端的请求
- 服务器若批准此请求，则使用 临时端口 与客户端进行通信。
- 每个数据包的编号都有变化（从1开始）
- 每个数据包都要得到ACK的确认，如果出现超时，则需要重新发送最后的数据包或ACK包
- 数据长度以512Byte传输的，小于512Byte的数据意味着数据传输结束
TFTP协议分析
差错码：
0 未定义,差错错误信息
1 File not found.
2 Access violation.
3 Disk full or allocation exceeded.
4 illegal TFTP operation.
5 Unknown transfer ID.
6 File already exists.
7 No such user.
8 Unsupported option(s) requested.
#include "../header.h"#define S_IP "192.168.125.30" #define S_PORT 69typedef struct file_header {int size;char *file_report; } file_header_report; char buf[516] = ""; char fileName[128] = {0}; int sockfd = -1; int data_num = 0;void download_file(struct sockaddr_in *addr); void upload_file(struct sockaddr_in *addr); void dealerror(short errno); file_header_report get_report_RW(short type); file_header_report get_report_ACK(short type, short blknumber);int main(int argc, char const *argv[]) {// 服务器地址 ,初始地址用于链接请求，但是不是用于实际数据交互struct sockaddr_in addr;addr.sin_family = AF_INET;addr.sin_port = htons(S_PORT);addr.sin_addr.s_addr = inet_addr(S_IP);char choose = 0;while (1) {printf("**************************\n");printf("******** 1. 下载 *********\n");printf("******** 2. 上传 *********\n");printf("******** 3. 退出 *********\n");printf("**************************\n");printf("请输入>>> ");choose = getchar();while (getchar() != 10) {};switch (choose) {case '1':download_file(&addr);break;case '2':upload_file(&addr);break;case '3':exit(EXIT_SUCCESS);break;default:printf("输入错误！请重新输入\n");}}close(sockfd);return 0; } void upload_file(struct sockaddr_in *addr) {if (sockfd == -1) { // 判断一下，防止重复创建套接字sockfd = socket(AF_INET, SOCK_DGRAM, 0);if (sockfd < 0) {perror("socket");return;}}// 发送上传请求printf("请输入要上传的文件名：\n");file_header_report file_report = get_report_RW(2);if (access(fileName, F_OK) != 0) {printf("文件不存在\n");return;}data_num = 0;if (sendto(sockfd, file_report.file_report, file_report.size, 0,(struct sockaddr *)addr, sizeof(struct sockaddr)) == -1) {perror("1111sendto 数据包");return;}// recv_addr 用于 实际数据交互的地址struct sockaddr_in recv_addr;socklen_t recv_addr_len = sizeof(recv_addr);int read_size = recvfrom(sockfd, buf, 516, 0, (struct sockaddr *)&recv_addr,&recv_addr_len);short *first_no = (short *)buf;short *blk_num = (short *)(buf + 2);// 处理报错信息 == 5if (ntohs(*first_no) == 5) {dealerror(ntohs(*blk_num));return;}if (ntohs(*first_no) == 4) {int upload_fd = open(fileName, O_RDONLY);if (upload_fd < 0) {perror("open");return;}while (1) {// 发送数据包bzero(buf, sizeof(buf));// 拼接数据包short *p1 = (short *)buf;*p1 = htons(3);short *p2 = (short *)(buf + 2);*p2 = htons(data_num);int file_size = read(upload_fd, buf + 4, 512);if (file_size < 0) {perror("read");exit(1);}if (sendto(sockfd, buf, file_size + 4, 0,(struct sockaddr *)&recv_addr,sizeof(recv_addr)) == -1) {perror("sendto 数据包");exit(1);}bzero(buf, sizeof(buf));int read_size_n =recvfrom(sockfd, buf, 4, 0, (struct sockaddr *)&recv_addr,&recv_addr_len);short *first_noe_n = (short *)buf;short *blk_nume_n = (short *)(buf + 2);// 确认ACK包// 编号是否与本地的标号一致，一致的话就进行下一个编号的数据传送if (ntohs(*first_noe_n) == 4 && ntohs(*blk_nume_n) == data_num) {// 这种情况说明本次上传成功data_num++;} else {printf("上传失败\n");if (ntohs(*first_no) == 5) {dealerror(ntohs(*blk_num));return;}break;}// 如果最后一次读取，就结束循环if (file_size < 512) {printf("上传成功\n");break;}}} else {printf("上传失败\n");} } // 下载 void download_file(struct sockaddr_in *addr) {if (sockfd == -1) { // 判断一下，防止重复创建套接字sockfd = socket(AF_INET, SOCK_DGRAM, 0);if (sockfd < 0) {perror("socket");return;}}// 发送下载请求printf("请输入要下载的文件名：\n");file_header_report file_report = get_report_RW(1);if (sendto(sockfd, file_report.file_report, file_report.size, 0,(struct sockaddr *)addr, sizeof(struct sockaddr)) == -1) {perror("sendto 数据包");return;}struct sockaddr_in recv_addr;socklen_t recv_addr_len = sizeof(recv_addr);while (1) {// 接收数据包// 数据包返回的服务器端地址需要存在recv_addr，因为服务器处理数据的端口并非原来端口，// 该地址recv_addr 用于后续的ack包 发送给服务器用于确认bzero(buf, sizeof(buf));int read_size = recvfrom(sockfd, buf, 516, 0,(struct sockaddr *)&recv_addr, &recv_addr_len);int download_fd = open(fileName, O_RDWR | O_CREAT | O_APPEND, 0666);if (download_fd < 0) {perror("open");return;}short *first_no = (short *)buf;short *blk_num = (short *)(buf + 2);// 处理报错信息 == 5if (ntohs(*first_no) == 5) {dealerror(ntohs(*blk_num));break;}// 这是数据包 == 3if (ntohs(*first_no) == 3) {if (read_size > 4) {write(download_fd, buf + 4, read_size - 4);}// 发送ACK*first_no = htons(4);char newbuf[4] = {0};short *p1 = (short *)newbuf;*p1 = htons(4);short *p2 = (short *)(newbuf + 2);*p2 = *blk_num;if (sendto(sockfd, newbuf, 4, 0, (struct sockaddr *)&recv_addr,sizeof(recv_addr)) == -1) {perror("sendtoACK\n");}printf("发送ACK成功\n");if (read_size < 516) {printf("下载完成\n");break;}}close(download_fd);} } // 处理报错信息 void dealerror(short errno) {int erno = 0;switch (errno) {case 1:printf("File not found");break;case 2:printf("Access violation");break;case 3:printf("Disk full or allocation exceeded");break;case 4:printf("illegal TFTP operation");break;case 5:printf("Unknown transfer lD");break;case 6:printf("File already exists");break;case 7:printf("No such user");break;case 8:printf("Unsupported option(s) requested");break;default:break;}return; }/*** @description: 组装请求体数据包* @param {short} type 1--- 下载 2---上传* @return {*}*/ file_header_report get_report_RW(short type) {bzero(buf, sizeof(buf));fgets(fileName, sizeof(fileName), stdin);if (strlen(fileName) > 1) {fileName[strlen(fileName) - 1] = '\0';}short *p1 = (short *)buf;*p1 = htons(type);char *p2 = buf + 2;strcpy(p2, fileName);char *p4 = p2 + strlen(p2) + 1;strcpy(p4, "octet");int size = 2 + strlen(p2) + strlen(p4) + 2;file_header_report fh = {size, buf};return fh; }
