#include<myhead.h>
int task_download(int client_fd,struct sockaddr_in serve_info)
{
	//定义变量存储下载请求包
	char buf[516] = "";
	//定义变量存储文件名
	char filename[40] = "";
	printf("请输入文件名：");
	scanf("%s",filename);
	getchar();
	//组装请求包
	short *p1 = (short *)buf;
	*p1 = htons(1);                 //表明要下载
	char *p2 = buf+2;           //文件名段
	strcpy(p2, filename);
	char *p4 = p2+strlen(p2)+1;    //模式段
	strcpy(p4, "octet");
	int size = 4 + strlen(p2) + strlen(p4);      //要发送数据的大小
	if(sendto(client_fd,buf,size,0,(struct sockaddr*)&serve_info,sizeof(serve_info))==-1)
	{
		perror("sendto error");
		return -1;
	}
	printf("已经向服务器发送下载请求\n");
	//首先判断文件在当前文件夹下是否存在
	if(access(filename,F_OK)==0) //-1不存在 0存在
	{
		//存在
		printf("目录下已经存在该文件名的文件了，将重新写入\n");
	}
	int downfd=-1;
	if((downfd=open(filename,O_WRONLY|O_CREAT|O_TRUNC,0664))==-1)
	{
		perror("open error");
		return -1;
	}
	//与服务器发送来的包进行解析分析与应答
	while(1)
	{		
		bzero(buf, sizeof(buf));
		int res = -1;
		if((res = recvfrom(client_fd, buf, sizeof(buf), 0,NULL,NULL)) == -1){
			perror("recvfrom error");
			return -1;
		}
		short *p1 = (short *)buf;
		if(*p1 == htons(3))
		{
			write(downfd, buf+4, res-4);
			*p1 = htons(4);  
			sendto(client_fd, buf, 4, 0, (struct sockaddr *)&serve_info, sizeof(serve_info));
			if(res < 516)
			{
				break;
			}
		}
		else
		{
			printf("未知错误，错误码: %d\n", buf[3]);
			close(downfd);
			return -1;
		}
	}
	return 0;
}
int main(int argc, const char *argv[])
{
	if(argc!=2)
	{
		printf("input error\n note->./a.out ip\n");
		return -1;
	}
	int client_fd=-1;
	if((client_fd=socket(AF_INET,SOCK_DGRAM,0))==-1)
	{
		perror("socket error");
		return -1;
	}
	//recvfrom/sendto
	struct sockaddr_in serve_info;
	serve_info.sin_family=AF_INET;
	serve_info.sin_port=htons(69);//UDP对应的tftp端口号
	serve_info.sin_addr.s_addr=inet_addr(argv[1]);
	int mune=-1;
	while(1)
	{
		system("clear");	
		printf("\t\t=======================1->下载=======================\n");
		printf("\t\t=======================2->上传=======================\n");
		printf("\t\t=======================3->退出=======================\n");
		printf("请选择功能->");	
		scanf("%d",&mune);
		getchar();
		switch(mune)
		{
		case 1:
			task_download(client_fd,serve_info);
			break;
		case 2:
			//task_upload();
			break;
		case 3:
			goto quit;
		default:
			printf("input error\n");
			break;
		}
		while(getchar()!='\n');
	}
quit:
	close(client_fd);
	return 0;
}