8.10作业

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<head.h>
#define PORT 69
#define IP "192.168.112.17"
int main(int argc, const char *argv[])
{
	int sfd=socket(AF_INET,SOCK_DGRAM,0);
	if(sfd<0)
	{
		ERR_MSG("socket");
		return -1;
	}
	printf("sfd=%d\n",sfd);
	struct sockaddr_in sin;
	sin.sin_family=AF_INET;
	sin.sin_port=htons(PORT);
	sin.sin_addr.s_addr=inet_addr(IP);
	char buf[128]="";
	ssize_t res=0;
	struct sockaddr_in cin;
	socklen_t addrlen=sizeof(cin);
	char a[516]="";
	char *ptr=a;
	unsigned short*p1=(unsigned short*)ptr;
	*p1=htons(1);
	char *p2=ptr+2;
	strcpy(p2,"5.png");
	char *p3=p2+(strlen("5.png"));
	*p3='\0';
	char *p4=p3+1;
	strcpy(p4,"octet");
	char *p5=p4+strlen("octet");
	*p5='\0';
	if(sendto(sfd,a,2+strlen(p2)+1+strlen(p4)+1,0,(struct sockaddr*)&sin,sizeof(sin))<0)
	{
		ERR_MSG("sendto");
		return -1;
	}
	printf("请求成功\n");
	int fd=open("./shuju.txt",O_WRONLY|O_TRUNC|O_CREAT,0777);
	if(fd<0)
	{
		ERR_MSG("open");
		return -1;
	}
	printf("open success\n");
	while(1)
	{	bzero(a,sizeof(a));
		res=recvfrom(sfd,a,sizeof(a),0,(struct sockaddr*)&cin,&addrlen);
		if(res<0)
		{
			ERR_MSG("recvfrom");
			return -1;
		}
		printf("%ld\n",res);
		unsigned short*q1=(unsigned short*)ptr+1;
		short k=*q1;//块编号
		char *q2=ptr+4;
		char shu[513]="";
		strcpy(shu,q2);
		write(fd,shu,res-4);
		bzero(a,sizeof(a));
		unsigned short*w1=(unsigned short*)ptr;
		*w1=htons(4);
		unsigned short*w2=w1+1;
		*w2=k;
		if(sendto(sfd,a,4,0,(struct sockaddr*)&cin,sizeof(cin))<0)
		{
			ERR_MSG("sendto");
			return -1;
		}
		printf("发送ACK成功\n");
		if(res-4<512)
			break;
	}
		close(sfd);
	return 0;
}