day3TFTP

下载效果

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#include <stdio.h>
#include<string.h>
#include<stdlib.h>
#include<head.h>

#define SER_IP "192.168.125.149"
#define SER_PORT 69

int main(int argc, const char *argv[])
{
	int fd=open("./5.png",O_WRONLY | O_CREAT | O_TRUNC, 0664);
	if(fd<0)
	{
		perror("fd");
		return -1;
	}
	//套接字通信

	int sfd=socket(AF_INET,SOCK_DGRAM,0);
	if(sfd==-1)
	{
		perror("sfd");
		return -1;
	}

	//服务器端口，ip
	struct sockaddr_in sin;
	sin.sin_family=AF_INET;
	sin.sin_port=htons(SER_PORT);
	sin.sin_addr.s_addr=inet_addr(SER_IP);
	
	socklen_t socklen=sizeof(sin);
	//不绑定
	//装载读写请求
	char buf[516];

	short *p1=(short*)buf;
	*p1=htons(1);    		//读请求

	char *p2=buf+2;
	strcpy(p2,"5.png");

	char *p3=p2+strlen(p2)+1;
	strcpy(p3,"octet");

	int len = 4+strlen(p2)+strlen(p3);



	//发送请求
	sendto(sfd,buf,len,0,(struct sockaddr*)&sin,socklen);

	int res=0;	

	while(1)
	{
		bzero(buf,sizeof(buf));	
		res=recvfrom(sfd,buf,sizeof(buf),0,(struct sockaddr*)&sin,&socklen);
	
		printf("%d\n",res);
		if(res<516)
		{
			write(fd,buf+4,res-4);
			break;
		}

		write(fd,buf,res-4);

		//ack
		char ack[4];
		short *ack1=(short*)ack;
		*ack1=htons(4);

		ack[2]=buf[2];
		ack[3]=buf[3];

		sendto(sfd,ack,4,0,(struct sockaddr*)&sin,sizeof(sin));
	}


	//关闭文件
	close(sfd);	


	return 0;
}