TFTP协议实现

最新推荐文章于 2024-07-23 14:04:07 发布

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本文介绍了TFTP协议的基础知识，结合Linux环境探讨了如何在实践中应用TFTP服务，包括设置服务器端口、处理socket编程中的问题以及在不同场景下的应用。同时，文章还提及了与Linux操作系统、网络服务和故障排查相关的其他技术话题。

依据TFTP协议的规定,实现通过TFTP来实现文件的传输功能。

TFTP Server：

实现功能：实现TFTP服务器，可以让用户下载文件

命令： tftps rootdir（请求的文件路径）

实现思路：

监听69端口

接收到数据后，fork子进程服务该客户端

分析客户端的请求报文，检查是否有扩展参数

如果有扩展参数，则回应OACK，并等待客户端对OACK做回应

启动传输数据

文件传输结束后子进程退出

tftps.c

int main(int argc,char **argv) { int server_sockfd,client_sockfd; int server_len,client_len; struct sockaddr_in server_address; struct sockaddr_in client_address; char recv_buf[516] = {}; char send_buf[516] = {}; char recv_cmd[4] = {}; int byte; int n = 0; int pid,fd; server_sockfd = socket(AF_INET,SOCK_DGRAM,0); bzero(&server_address,sizeof(server_address)); server_address.sin_family = AF_INET; server_address.sin_addr.s_addr = inet_addr("192.168.220.59");

//我的PC机IP地址 server_address.sin_port = htons(69); server_len = sizeof(server_address); bind(server_sockfd,(struct sockaddr *)&server_address,server_len); if((byte = recvfrom(server_sockfd,recv_buf,516,0,(struct sockaddr *)&client_address,sizeof(struct sockaddr))) == -1) { perror("recvfrom"); exit(0); }

//创建一个进程来分析收到的报文信息 if((pid = fork()) == 0) { if(recv_buf[1] == 1) //为下载文件请求 { printf("this is a read request:\n"); if((fd = open(recv_buf[2],O_RDONLY)) < 0) { perror("open"); exit(0); }

while(1) { recvfrom(server_sockfd,recv_cmd,4,0,(struct sockaddr *)&client_address,sizeof(struct sockaddr)); read(fd,send_buf+4,sizeof(send_buf+4));

//将文件内容读入数据区 send_buf[1] = 3;

//构造报文 if((byte = sendto(server_sockfd,send_buf,516,0,(struct sockaddr *)&client_address,sizeof(struct sockaddr))) == 516) { sendto(server_sockfd,send_buf,4,0,(struct sockaddr *)&client_address,sizeof(struct sockaddr)); send_buf[3]++; }

//TFTP每次发送512个字节，附带四个字节的报文信息，小于516时就代表文件传输完毕 else exit(0); } } if (recv_buf[1] == 2) //为上传文件请求 { printf("this is a write request:\n"); if((fd = open(recv_buf[2],O_RDWR|O_CREAT)) < 0) { perror("open"); exit(0); } while(1) { recvfrom(server_sockfd,recv_cmd,4,0,(struct sockaddr *)&client_address,sizeof(struct sockaddr)); recvfrom(server_sockfd,recv_buf,512,0,(struct sockaddr *)&client_address,sizeof(struct sockaddr)); write(fd,send_buf+4,sizeof(send_buf+4)); send_buf[1] = 3; if((byte = sendto(server_sockfd,send_buf,516,0,(struct sockaddr *)&client_address,sizeof(struct sockaddr))) == 516) { sendto(server_sockfd,send_buf,4,0,(struct sockaddr *)&client_address,sizeof(struct sockaddr)); send_buf[3]++; } else exit(0); } } close(fd); } else return 0; }

TFTP Client：

实现功能：通过tftp下载文件

命令：tftpc ip file

实现思路：

构造请求报文，送至服务器

等待服务器回应

分析服务器回应

循环接收数据，直到接收到的数据包小于标准数据包

tftpc.c

#include <sys/types.h> #include <sys/socket.h> #include <stdio.h> #include <sys/un.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <arpa/inet.h> #include <netinet/in.h> #include <fcntl.h> int main(int argc,char **argv) { int sockfd; struct sockaddr_in server; char read_cmd[100] = {}; char buf[516]=""; char *str; int addrlen = sizeof(server); int fd,rew,recv,read_num,send_num; int n = 0,num; char filename[100] = {}; if(argc == 1) { printf("ERROR:please input a filename:\n"); exit(0); } else if(argc == 2) { strcpy(filename,argv[1]); } bzero(&server, sizeof(struct sockaddr_in)); server.sin_family = AF_INET; server.sin_port = htons(69); server.sin_addr.s_addr = inet_addr("192.168.220.59"); printf("please input read?write:1 or 2: "); scanf("%d",&num); rew = sprintf(read_cmd,"%c%c%s%c%s%c",0,num,filename,0,"octet",0); sockfd = socket(AF_INET, SOCK_DGRAM, 0); if(sockfd < 0) { perror("Invalid socket"); exit(1); } sendto(sockfd, read_cmd, rew, 0, (struct sockaddr*)&server, sizeof(struct sockaddr)); if((fd = open(filename, O_RDWR|O_CREAT))<0) { perror("open"); exit(1); } if (num == 1) { num = 0; do{ bzero(buf,sizeof(buf)); recv = recvfrom(sockfd, buf, 516, 0, (struct sockaddr*)&server, &addrlen); write(fd, buf+4, 512); if(n == 255) { num++; n = -1; } rew = sprintf(read_cmd,"%c%c%c%c",0,4,num,++n); sendto(sockfd, read_cmd, rew, 0, (struct sockaddr*)&server, sizeof(struct sockaddr)); }while(recv == 516); } if( num == 2) { do{ bzero(buf,sizeof(buf)); recvfrom(sockfd, buf, 4, 0, (struct sockaddr*)&server, &addrlen); buf[1] = 3; if((unsigned char)buf[3]==255) { buf[2]++; } buf[3]++; read_num = read(fd,buf+4,512); printf("%d\n",send_num); send_num = sendto(sockfd, buf, read_num+4, 0, (struct sockaddr*)&server, sizeof(struct sockaddr)); }while(read_num==512); } close(fd); return 0; }