day3：基于UDP模型的简单文件下载

思维导图

tftp文件下载客户端实现

#include 
#define SER_PORT 69
#define SER_IP "192.168.125.223"
int link_file()
{
	int sfd=socket(AF_INET,SOCK_DGRAM,0);
	if(sfd==-1)
	{
		perror("socket error");
		return -1;
	}
	return sfd;
}
int filedownload()
{
	//创建文件描述符用于下载传输过来的数据包
	int wfd=-1;
	if((wfd=open("./copy_file",O_WRONLY|O_CREAT|O_TRUNC,0664))==-1)
	{
		perror("open error:");
		return -1;
	}
	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);
	int sfd=-1;
	if((sfd=link_file())==-1)
	{
		printf("链接失败\n");
		return -1;
	}
	//封装请求下载数据包
	//第一块
	char buf[516]="";
	short *p1=(short*)buf;
	*p1=htons(1);
	//第二模块
	printf("请输入你要下载的文件:");
	char file[50];
	scanf("%s",file);
	char *p2=buf+2;
	strcpy(p2,file);
	//第三模块
	char *p3=p2+strlen(p2)+1;
	strcpy(p3,"octet");
	int len=4+strlen(p2)+strlen(p3);
	sendto(sfd,buf,len,0,(struct sockaddr*)&sin,sizeof(sin));
	while(1)
	{
		int res=0;
		if((res=recvfrom(sfd,buf,sizeof(buf),0,(struct sockaddr*)&sin,&socklen))<0)
		{
			perror("recvfrom error:");
			return -1;
		}
		char *data_point=buf+4;
		short *cmd_point=(short*)buf;
		short *block_point=(short*)(buf+2);
		if(res<516)
		{
			write(wfd,data_point,res-4);
			printf("文件拷贝完成!\n");
			break;
		}
		write(wfd,data_point,512); 
		//完成了一次拷贝要向客户端发送ACK包
		char ack[4];
		short *p1=(short*)ack;
		short *p2=(short*)(ack+2);
		*p1=htons(4);
		*p2=*block_point;
		sendto(sfd,ack,4,0,(struct sockaddr*)&sin,sizeof(sin));
	}
}
int onload()
{
	int sfd=link_file();
	system("ls");
	printf("请问你要上传的文件是:");
	char file[50];
	scanf("%s",file);
	//未完成
}
int main(int argc, const char *argv[])
{
	while(1)
	{
		printf("==========欢迎使用文件下载客户端==========\n");
		printf("1、下载文件\t2、上传文件\t0、退出\n");
		printf("请输入你要执行的操作:");
		int cmd;
		scanf("%d",&cmd);
		switch(cmd)
		{
		case 1:
			{
				filedownload();
				break;
			}
		case 2:
			{
				//fileonload();
				break;
			}
		case 0:
			{
				system("clear");
				return 0;
			}
		default:
			{
				printf("输入有误\n");
			}
		}
		system("clear");
	}
	return 0;
}