开发环境：ubuntu

所用知识点：c，socket, tcp/ip协议

A)本实验主要实现tftp协议的服务器与客户端。

服务器实现功能有：

1)接收处理客户端请求，上传下下载文件

2)进行用户验证

3)对传输数据进行加密解密处理

4)生成日志文件

客户端实现功能有：

1)向服务器发出请求，上传或下载文件

2)对传输数据加密解密

3)对用户信息进行MD5加密

B)相关代码实现：

宏定下：

#ifndef MAKEWORD

#define MAKEWORD(l,h) ((unsigned short)(((unsigned char)(l))|(((unsigned short)(unsigned char)(h))<<8)))

#endif

#define WSA_MAJOR_VERSION 1

#define WSA_MINOR_VERSION 1

#define WSA_VERSION MAKEWORD(WSA_MAJOR_VERSION, WSA_MINOR_VERSION)

#define TFTP_OCTET 1

#define TFTP_WSTAT_FIRSTACK 0

#define TFTP_WSTAT_NEXTACK 1

#define TFTP_WSTAT_LASTACK 2

#define TFTP_RRQ 1 //读请求

#define TFTP_WRQ 2 //写请求

#define TFTP_DATA 3 //数据

#define TFTP_ACK 4 //ACK

#define TFTP_ERROR 5 //Error

#define MAX_RETRY 3 //大重复次数

#define TFTP_NOTEND_DATALEN 512+2+2 //数据块长度

//错误种类

#define Not_defined 0

#define File_not_found 1

#define Access_violation 2

#define Disk_full 3

#define Illegal_TFTP_operation 4

#define Unknown_port 5

#define File_already_exists 6

#define No_such_user 7

#define Time_out 8

#define Read_file_Error 9

#define Cannot_create_file 10

#define passwd_or_user_error 11

包的填充：

#include "define.h"

#include

#include

int makeack(unsigned short num,char *buffer,int size );

int makedata(unsigned short num,char *data,int datasize,char *buffer,int bufsize);

int makeerr(unsigned short num,char *buffer);

//ACK包填充

int makeack(unsigned short num,char *buffer,int size )

{

int pos = 0;

buffer[pos] = 0;

pos++;

buffer[pos] = TFTP_ACK; //操作码为04

pos++;

buffer[pos] = (char)(num>>8);//块号2个字节

pos++;

buffer[pos] = (char)num;

pos++;

return pos;

}

//Data包填充

int makedata(unsigned short num,char *data,int datasize,char *buffer,int bufsize)

{

int pos = 0;

buffer[pos] = 0;

pos++;

buffer[pos] = TFTP_DATA; //操作码为03

pos++;

buffer[pos] = (char)(num>>8);//块号

pos++;

buffer[pos] = (char)num;

pos++;

memcpy(&buffer[pos],data,datasize);//填充数据

pos = pos + datasize;

return pos;

}

//ERROR包填充

int makeerr(unsigned short num,char *buffer)

{

int pos=0;

buffer[pos]=0;

pos++;

buffer[pos]=TFTP_ERROR; //操作码为05

pos++;

buffer[pos] = (char)(num>>8); //错误种类号

pos++;

buffer[pos] = (char)num;

pos++;

return pos;

}

日志log.c实现

#include

static char log[100]; //日志

char datetime[20]; //记录时间变量

int timeout=2,retran=3; //服务器参数

void record(int a,struct sockaddr_in *sin,char *file)

{

char tem[60];

time_t t=time(0); //初始化日历时间

strftime(datetime,sizeof(datetime),"%y/%m/%d %X",localtime(&t));//将时间格式化

strcat(log,datetime);//将时间写入记录

//将字符串格式化

bzero(&tem,sizeof(tem));

if(a==1)

sprintf(tem," 收到来自 %s 上传文件 %s 的请求。\n",inet_ntoa(sin->sin_addr),file);

if(a==2)

sprintf(tem," %s 上传文件 %s 完毕。\n",inet_ntoa(sin->sin_addr),file);

if(a==3)

sprintf(tem," 收到来自 %s 下载文件 %s的请求。\n",inet_ntoa(sin->sin_addr),file);

if(a==4)

sprintf(tem," %s 下载文件 %s 完毕。\n",inet_ntoa(sin->sin_addr),file);

if(a==5)

sprintf(tem," 出现出错，操作中断。\n",inet_ntoa(sin->sin_addr),file);

//将具体信息写入记录

strcat(log,tem);

FILE *write;

if((write=fopen("log.txt","a+"))==NULL)

printf("打开记录文件失败\n");

//将记录写入文件

fwrite(&log,strlen(log),1,write);

fclose(write);

bzero(&log,sizeof(log));

}

加密解密实现

#include

#include

#include

int decrypt(FILE *in,FILE *out);

int encrypt(FILE *in,FILE *out);

unsigned char atoh(char *hexstr);

int encrypt(FILE *in,FILE *out)

{

if(in == NULL || out == NULL)

{

fprintf(stderr,"%s\n","file error!\n");

return -1;

}

unsigned char hex;

while(fread(&hex,1,1,in))

{

hex = ~hex^0x98;

fprintf(out,"%02X",hex);

}

return 0;

}

int decrypt(FILE *in,FILE *out)

{

if(in == NULL || out == NULL)

{

fprintf(stderr,"%s\n","file error!");

return -1;

}

unsigned char hexstr[3];

unsigned char hex = 0;

int i = 0;

while(fread(hexstr,2,1,in))

{

hex = atoh(hexstr);

hex = ~(hex ^ 0x98);

fwrite(&hex,1,1,out);

}

return 0;

}

/* convert string to hex */

unsigned char atoh(char *hexstr)

{

int i;

int hextodec[]={0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};

char chtodec[] = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};

unsigned char hexnum = 0;

for(i = 0; i < sizeof(chtodec); ++i)

{

if(hexstr[0] == chtodec[i])

{

hexnum += hextodec[i]*16;

}

}

for(i = 0; i < sizeof(chtodec); ++i)

{

if(hexstr[1] == chtodec[i])

{

hexnum += hextodec[i];

}

}

return hexnum;

}

上传数据：

//上传函数

void upload(struct sockaddr_in sour_addr,char buffer[])

{

char send_buffer[1024] = {0};

char recv_buffer[1024] = {0};

struct sockaddr_in dest_addr;

struct timeval timeout = {10,0};

int sour_len = 0;

int ret = 0;

int len = 0;

int flen = 0;

fd_set fdr;

unsigned short lastdata = 0;

unsigned short blocknum = 0;

FILE *file;

FILE *decrypt_file = NULL;

char filename[256];

//获取文件名

strcpy(filename,buffer+2);

dest_addr.sin_family = AF_INET;

dest_addr.sin_port = sour_addr.sin_port;

dest_addr.sin_addr.s_addr = inet_addr(desthost);//

//如果本地存在同名文件

if((file=fopen(filename,"rb"))!=NULL)

{

//发送一个error包,报告存在同名文件

printf("***存在同名文件***");

len = makeerr(File_already_exists,send_buffer);

ret = sendto(sock,send_buffer,len,0,(struct sockaddr *)&dest_addr,sizeof(dest_addr));

record(5,&sour_addr,filename);

return;

}

//建立文件

if((file=fopen(filename,"w+b"))==NULL)

{

//如果失败,发送error包

printf("创建文件失败\n");

len = makeerr(Cannot_create_file,send_buffer);

ret = sendto(sock,send_buffer,len,0,(struct sockaddr *)&dest_addr,sizeof(dest_addr));

record(5,&sour_addr,filename);

return;

}

//发送ACK

len = makeack(blocknum,send_buffer,sizeof(send_buffer));

ret = sendto(sock,send_buffer,len,0,(struct sockaddr *)&dest_addr,sizeof(dest_addr));

blocknum++;

while(1){

FD_ZERO(&fdr);

FD_SET(sock, &fdr);

ret = select(sock+1, &fdr, NULL,NULL, &timeout);

if(-1==ret)

{

printf("Socket 错误\n");

fclose(file);

record(5,&sour_addr,filename);

return;

}

else

{

if(0==ret)

{

printf("超时\n");

fclose(file);

record(5,&sour_addr,filename);

return;

}

else

{

if (FD_ISSET(sock,&fdr))

{

//接收数据包

sour_len = sizeof(struct sockaddr);

ret = recvfrom(sock,recv_buffer,sizeof(recv_buffer),0,(struct sockaddr *)&sour_addr,&sour_len);

//如果是数据包

if(TFTP_DATA==recv_buffer[1])

{

lastdata = MAKEWORD(recv_buffer[3],recv_buffer[2]); //块号

//如果块号正确

if(lastdata == blocknum)

{

//发送ACK包

len = makeack(blocknum,send_buffer,sizeof(send_buffer));

sendto(sock,send_buffer,len,0,(struct sockaddr *)&dest_addr,sizeof(dest_addr));

blocknum++;

if(blocknum > 65535)

blocknum = 0;

//后一包

if(ret < TFTP_NOTEND_DATALEN)

{

//写入文件

fwrite(&recv_buffer[4],1,ret-4,file);

flen = flen + ret -4;

#ifdef _DEBUG_

printf("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__);

printf("*****传输结束,共收到 %d 字节*****\n",flen);

#endif

rewind(file);

if((decrypt_file =fopen("decrypt_temp","wb+"))==NULL){

printf("decrypt file open error \n");

return;

}

decrypt(file, decrypt_file);

fclose(decrypt_file);

rename("decrypt_temp", filename);

fclose(file);

record(2,&sour_addr,filename);

return;

}

else

{

fwrite(&recv_buffer[4],1,512,file);

flen = flen + 512;

#ifdef _DEBUG_

printf("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__);

printf("已收到 %d 字节\n",flen);

#endif

}

}

else

{

//重新发送ACK包

printf("数据包块号错误.\n");

sendto(sock,send_buffer,len,0,(struct sockaddr *)&dest_addr,sizeof(dest_addr));

}

}

}

}

}

}

}

C)客户端与服务都配有工程管理器，可通过make 完成编译。

D)实现效果：