8.10网络编程

网络编程"/>

8.10网络编程

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

代码：

#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<string.h>
#include<stdlib.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<sys/stat.h>
#include<fcntl.h>
#define MSG(msg)  do{\printf("__%d__",__LINE__);\perror(msg);\}while(0)int main(int argc, const char *argv[])
{	int pp = socket(AF_INET,SOCK_DGRAM,0);struct sockaddr_in dd;dd.sin_family = AF_INET;dd.sin_port = htons(69);dd.sin_addr.s_addr = inet_addr(argv[1]);//	char buf[128] = "";printf("请输入要下载的文件:");char filename[20];scanf("%s",filename);//读写请求	//操作码char buf[128] = "";short int *pa = (short int *)buf;*pa = htons(1);//文件名char*pb = buf+2;strcpy(pb,filename);//0char*pc = pb+strlen(pb);*pc = 0;//模式char *pd = pc+1;strcpy(pd,"octet");pd[strlen(pd)] = 0;//连接服务器int size ;size = 2+strlen(pb)+1+strlen(pd);sendto(pp,buf,size,0,(struct sockaddr*)&dd,sizeof(dd));//数据包char brr[600];struct sockaddr_in cin;socklen_t addlen = sizeof(cin);//ACKchar crr[4]="";*(short int*)crr = htons(4);//块编号short int num=0;//下载到的文件int file = open("./111",O_WRONLY|O_CREAT|O_TRUNC,0664);	int res;while(1){//接收服务器发送数据包bzero(brr,sizeof(brr));res = recvfrom(pp,brr,sizeof(brr),0,(struct sockaddr*)&cin,&addlen);if(res<0){MSG("recvfrom");return -1;}//判断错误码/*short int *a1 = (short int*)brr;short int *a2 = (short int*)(brr+2);if(*a1==5){char*a3 = brr+4;printf("%s\n",a3);}*/write(file,brr+4,res-4);if(res<516)break;//赋值ACKshort int* p1 = (short int*)(brr+2);short int *p2 = (short int *)crr;p2++;*p2 = *p1;//发送ACKsendto(pp,crr,sizeof(crr),0,(struct sockaddr*)&cin,addlen);     }close(pp);close(file);return 0;
}

 结果：