网络编程:tftp上传下载 day3 work

基于UDP的tftp客户端：实现上传、下载功能。

ubuntu@ubuntu:~/internet/exercise/03_UDP$ cat 04_udptftp.c 
#include
#include
#include
#include
#include
#include
#include
#include
#include

int do_download(int cfd,struct sockaddr_in sin);
int do_upload(int cfd,struct sockaddr_in sin);

#define ERR_MSG(msg) do{\
	printf("line:%d\n",__LINE__);\
	perror(msg);\
}while(0)

#define PORT 69

#define N 516

int main(int argc, const char *argv[])
{
	if(argc<2)
	{
		printf("please input ip:\n");
		return -1;
	}

	//创建流式套接字
	int cfd = socket(AF_INET,SOCK_DGRAM,0);
	if(cfd<0)
	{
		ERR_MSG("socket");
		return -1;
	}

	//功能：允许端口快速被重用，快速被复用
	int reuse = 1;
	if(setsockopt(cfd,SOL_SOCKET,SO_REUSEADDR,&reuse,sizeof(reuse))<0)
	{
		ERR_MSG("setsockopt");
		return -1;
	}

	//填充服务器的地址信息结构体  AF_INET：man 7 ip
	struct sockaddr_in sin;
	sin.sin_family     =AF_INET;      
	sin.sin_port       =htons(PORT);  
	sin.sin_addr.s_addr=inet_addr(argv[1]);

	int choose;
	while(1)
	{
		printf("******************************\n");
		printf("*********1.download***********\n");
		printf("*********2.upload*************\n");
		printf("*********3.exit***************\n");
		printf("******************************\n");
		
		printf("please input the option:\n");
		scanf("%d",&choose);
		getchar();

		switch(choose)
		{
		case 1:
			do_download(cfd,sin);
			break;
		case 2:
			do_upload(cfd,sin);
			break;
		case 3:
			goto END;
			break;
		default:
			printf("input fasle\n");
		}
	}

END:
	close(cfd);
	return 0;
}
//download
int do_download(int cfd,struct sockaddr_in sin)
{
	char filename[20]="";
	printf("please input the name of file which needs to download:");
	fgets(filename,sizeof(filename),stdin);
	filename[strlen(filename)-1] = 0;

	//发送下载请求包给服务器
	char buf[N]="";
	int size = sprintf(buf,"%c%c%s%c%s%c",0,1,filename,0,"octet",0);
	if(sendto(cfd,buf,size,0,(struct sockaddr*)&sin,sizeof(sin))<0)
	{
		ERR_MSG("sendto");
		return -1;
	}
	//循环接收发送应答包
	ssize_t recv_len;
	socklen_t len1 = sizeof(sin);	
	int flag = 0;
	unsigned short num = 1;
	int fd =-1;
	while(1)
	{	
		bzero(buf,sizeof(buf));
		recv_len = recvfrom(cfd,buf,N,0,(struct sockaddr*)&sin,&len1);
		if(recv_len<0)
		{
			ERR_MSG("recvfrom");
			return -1;
		}

		if(3==buf[1])  //数据包操作码是2bytes，操作码3位于buf[1]数组高位,低位是0x00
		{
			if(0==flag)  //在循环里边，为防止重复打开，故设置只有在第一次的时候打开文件
			{
				fd = open(filename,O_CREAT|O_WRONLY|O_TRUNC,0664);
				flag = 1;
			}
			if(htons(num)==*(unsigned short *)(buf+2)) //防止数据包重复到达
			{
				if(write(fd,buf+4,recv_len-4)<0)
				{
					ERR_MSG("write");
					break;
				}
				//回复ACK
				//数据包前四个字节除了操作码与ACK包不一样，其余全部一致
				buf[1]=4;  //将数据包的操作码改为ACK的操作码4，则发送数据包前四位就行
				if(sendto(cfd,buf,4,0,(struct sockaddr*)&sin,sizeof(sin))<0)
				{
					ERR_MSG("send");

				}
				if(recv_len-2-2<512)
				{
					printf("download complete\n");
					break;
				}
				num++;
			}
		}
		else if(5==buf[1])  //错误包
		{
			printf("----ERROR:%s",buf+4);
			break;
		}

	}
	close(cfd);

	return 0;
}
int do_upload(int cfd,struct sockaddr_in sin)
{
	char filename[20]="";
	printf("please input the name of file which needs to upload:");
	fgets(filename,sizeof(filename),stdin);
	filename[strlen(filename)-1] = 0;
	
	//判断想上传的文件是否存在
	int fd = open(filename,O_RDONLY);
	if(fd<0)
	{
		ERR_MSG("open");
		return -1;
	}
	//发送上传请求
	char buf[N]="";
	int size = sprintf(buf,"%c%c%s%c%s%c",0,2,filename,0,"octet",0);
	if(sendto(cfd,buf,size,0,(struct sockaddr*)&sin,sizeof(sin))<0)
	{
		ERR_MSG("sendto");
		return -1;
	}
	//循环接收发送数据包
	ssize_t recv_len;
	socklen_t len1 = sizeof(sin);	
	int flag = 0;
	unsigned short num = 0;
	while(1)
	{	
		bzero(buf,sizeof(buf));
		recv_len = recvfrom(cfd,buf,N,0,(struct sockaddr*)&sin,&len1);
		if(recv_len<0)
		{
			ERR_MSG("recvfrom");
			return -1;
		}

		if(4==buf[1])   //服务器返回应答包
		{
			//判断当前数据包的编号是否等于应答包的编号
			if(num ==ntohs(*(unsigned short*)(buf+2)))
			{
				//修改操作码为数据包
				buf[1]=3;
				//填充块编号
				num++;
				*(unsigned short*)(buf+2) = htons(num);
				//读取数据
				int res = read(fd,buf+4,sizeof(buf)-4);
				if(res<0)
				{
					ERR_MSG("read");
					return -1;
				}
				else if(0==res)
				{
					printf("upload complete\n");
					break;
				}
				//发送数据包
				if(sendto(cfd,buf,res+2+2,0,(struct sockaddr*)&sin,sizeof(sin))<0)
				{
					ERR_MSG("sendto");
					return -1;
				}
			}
			else
			{
				printf("file upload failed\n");
				break;
			}
		}
		else if(5==buf[1])
		{
			printf("---ERROR:%s\n",buf+4);
			break;
		}
	}
		
	return 0;
}