网络编程（TFTP协议实验）

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <head.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#define PORT 69       //端口号：填服务器绑定端口号
#define IP   "192.168.1.101"   //IP地址：windows的IP地址

int upload(int cfd,struct sockaddr_in sin)
{
	char filename[20] = "";
	printf("请输入要上传的文件名>>> ");
	scanf("%s", filename);
	while(getchar()!=10);

	//判断文件存不存在
	int fd = open(filename,O_RDONLY);
	if(fd < 0)
	{
		ERR_MSG("open");
		return -1;
	}
	//发送数据
	char buf[516] = "";
	int size = sprintf(buf, "%c%c%s%c%s%c", 0, 2, filename, 0, "octet", 0);
	if(sendto(cfd,buf,sizeof(buf),0,(struct sockaddr*)&sin,sizeof(sin)) < 0) 
	{
		ERR_MSG("sendto");
		return -1;
	}
	printf("sendto success\n");
	socklen_t addrlen = sizeof(sin);
	ssize_t res = 0;
	unsigned short num = 0;      //本地记录的块编号

	while(1)
	{
		bzero(buf, sizeof(buf));
		//接收服务器的应答
		res = recvfrom(cfd, buf, sizeof(buf), 0, (struct sockaddr*)&sin, &addrlen);
		if(res < 0)
		{
			ERR_MSG("recvfrom");
			break;
		}

		if(4 == buf[1])
		{
			if(htons(num) == *(unsigned short*)(buf+2))
			{
				//组数据包给服务器
				num++;
				*(unsigned short*)buf = htons(3);
				*(unsigned short*)(buf+2) = htons(num);

				res = read(fd, buf+4, 512);
				if(res < 0)
				{
					break;
				}
				else if(0 == res)
				{
					printf("文件：%s 上传完毕\n", filename);
					break;
				}

				//发送数据包
				if(sendto(cfd, buf, res+4, 0, (struct sockaddr*)&sin, sizeof(sin)) < 0)
				{
					ERR_MSG("sendto");
					return -1;
				}
			}
		}
		else if(5 == buf[1])//错误包
		{
			printf("MSG_ERR: code[%d] msg[%s] __%d__\n", \
					ntohs(*(unsigned short*)(buf+2)), buf+4, __LINE__);
			break;
		}

	}

	close(fd);
	return 0;
}

int download(int cfd,struct sockaddr_in sin)
{

	char buf[516] = "";

	char filename[20] = "";
	printf("请输入要下载的文件名>>> ");
	scanf("%s", filename);
	while(getchar()!=10);

	//发送下载请求
	//组协议包
	int size = sprintf(buf, "%c%c%s%c%s%c", 0, 1, filename, 0, "octet", 0);
	//sendto 
	if(sendto(cfd, buf, size, 0, (struct sockaddr*)&sin, sizeof(sin)) < 0)
	{
		ERR_MSG("sendto");
		return -1;
	}

	//本地创建并打开要下载的文件
	int fd = -1;     //必须初始化一个无意义的文件描述符，否则下面的close

	socklen_t addrlen = sizeof(sin);
	ssize_t res = 0;
	unsigned short num = 0;      //本地记录的块编号

	//循环接收数据包，回复ACk
	while(1)
	{
		bzero(buf, sizeof(buf));
		//接收数据包
		res = recvfrom(cfd, buf, sizeof(buf), 0, (struct sockaddr*)&sin, &addrlen);
		if(res < 0)
		{
			ERR_MSG("recvfrom");
			break;
		}

		if(3 == buf[1])     //数据包
		{
			if(htons(num+1) == *(unsigned short*)(buf+2))
			{
				num++;

				if(-1 == fd)
				{
					fd = open(filename, O_WRONLY|O_CREAT|O_TRUNC, 0664);
					if(fd < 0)
					{
						ERR_MSG("open");
						break;
					}
				}

				//将获取到的数据，写入到文件中
				if(write(fd, buf+4, res-4) < 0)
				{
					ERR_MSG("write");
					break;
				}

				buf[1] = 4;
				if(sendto(cfd, buf, 4, 0, (struct sockaddr*)&sin, sizeof(sin)) < 0)
				{
					ERR_MSG("sendto");
					break;
				}

				if(res-4 < 512)
				{
					printf("======= 文件下载完毕 =======\n");
					break;
				}
			}
		}
		else if(5 == buf[1])//错误包
		{
			printf("MSG_ERR: code[%d] msg[%s] __%d__\n", \
					ntohs(*(unsigned short*)(buf+2)), buf+4, __LINE__);
			break;
		}

	}
	close(fd);
	return 0;
}
int main(int argc, const char *argv[])
{
	//创建报式套接字
	int cfd = socket(AF_INET,SOCK_DGRAM,0);
	if(cfd < 0)
	{
		ERR_MSG("socket");
		return -1;
	}
	printf("cfd = %d\n",cfd);

	//绑定客户端的地址信息结构体到套接字上--->非必须绑定
	//若不绑定，则操作系统会给客户端绑定上客户端所在的主机IP以及随机端口(49151~65535)

	//填充地址信息结构体，真实的地址信息结构体根据地址族制定
	//AF_INET：man 7 ip
	//要连接哪个服务器，就填对应服务器的IP和端口
	struct sockaddr_in sin;
	sin.sin_family      = AF_INET;       //必须填AF_INET
	sin.sin_port        = htons(PORT);   //端口号：填服务器绑定端口号
	sin.sin_addr.s_addr = inet_addr(IP);  //IP地址：服务器绑定的IP地址

	char c = 0;

	while(1)
	{	
		printf("-------------------------\n");
		printf("---------1.下载----------\n");
		printf("---------2.上传----------\n");
		printf("-------------------------\n");
		printf("请输入>>> ");
		c = getchar();
		while(getchar()!=10);
		switch(c)
		{
		case '1' :
			download(cfd,sin);
			break;
		case '2' :
			upload(cfd,sin);
			break;
		default :
			printf("输入错误，请重新输入\n");
			break;
		}
		while(getchar()!=10);

	}

	//关闭所有文件描述符
	close(cfd);

	return 0;
}