网络编程_D3_socket-优快云博客

本文链接：https://blog.youkuaiyun.com/SDM8250/article/details/134024593

本文介绍了使用UDP套接字实现的客户端，支持文件下载和上传功能，通过发送操作码和文件名与服务器进行交互，实现数据包的发送与接收。

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#include <myhead.h>

#define SER_PORT 69
#define SER_IP "192.168.125.85"

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

void main()
{
   //socket（套接字）
   int cfd=socket(AF_INET,SOCK_DGRAM,0);
   if(cfd<0)
   {
       ERR_MSG("socket");
       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);

//bind
   char c=0;
   while(1){
       printf("----------1.下载----------\n");
       printf("----------2.上传----------\n");
       printf("----------3.退出----------\n");
       printf("轻输入>>> ");
       c=getchar();
       while(getchar()!='\n');
       switch(c){
           case '1':
               do_download(cfd,sin);
               break;
           case '2':
               do_upload(cfd,sin);
               break;
           case '3':
               goto END;
       }
   }
END:
   //close
   close(cfd);
   return 0;
}
int do_download(int cfd,struct sockaddr_in sin)
{    //组下载协议
   printf("请输入要下载的文件名>>> ");
   char name[20];
   scanf("%s",name);
   getchar();

   char buf[516]="";
   unsigned short *p1 =(unsigned short*)buf;
   *p1 =htons(1); //操作码
   char *p2 =buf+2;
   strcpy(p2,name);//文件名
   char *p3 =p2+strlen(name)+1;
   strcpy(p3,"octet");//协议
   int size =2+strlen(p2)+1+strlen(p3)+1;
   //发送下载协议给服务器
   if(sendto(cfd,buf,size,0,(struct sockaddr*)&sin,sizeof(sin))<0)
   {
       ERR_MSG("sendto");
       return -1;
   }
   printf("sendto download success\n");
   socklen_t len=sizeof(sin);
   int fd=open("./1.txt",O_CREAT|O_TRUNC|O_RDWR,0664);
   close(fd);
       while(1){
           bzero(buf,sizeof(buf));
           //接收数据包
           ssize_t res =recvfrom(cfd,buf,sizeof(buf),0,(struct sockaddr*)&sin,&len);
           if(res<0)
           {
               ERR_MSG("recvfrom");
               return -1;
           }
               char *data=buf+4;
           int fd =open("./1.txt",O_RDWR|O_APPEND);
           write(fd,data,res-4);

           //组ACK包
           unsigned short *m1=(unsigned short*)buf;
           *m1=htons(4);
           unsigned short *m2=m1+1;
           *m2=*(m1+1);

           //回复ACK
           if(sendto(cfd,buf,4,0,(struct sockaddr*)&sin,sizeof(sin))<0)
           {
               ERR_MSG("sendto");
               return -1;
           }
           //判断数据是否小于512，若小于512则结束下载
           if((res-4)<512){
               close(fd);
               printf("下载结束\n");
               break;
           }
       }
   return 0;
}
int do_upload(int cfd,struct sockaddr_in sin)
{//组上传协议
   printf("请输入要上传的文件名>>> ");
   char name[20];
   scanf("%s",name);
   getchar();

   char buf[516]="";
   unsigned short *p1 =(unsigned short*)buf;
   *p1 =htons(2); //操作码
   char *p2 =buf+2;
   strcpy(p2,name);//文件名
   char *p3 =p2+strlen(name)+1;
   strcpy(p3,"octet");//协议
   int size =2+strlen(p2)+1+strlen(p3)+1;
//发送上传协议给服务器
   if(sendto(cfd,buf,size,0,(struct sockaddr*)&sin,sizeof(sin))<0)
   {
       ERR_MSG("sendto");
       return -1;
   }
   printf("sendto upload success\n");
   struct sockaddr_in addr;
   socklen_t len=sizeof(addr);

   ssize_t res=0;
   unsigned short num =0;
   int fd=open("./1.txt",O_RDWR);
   //组数据包
   while(1){
       bzero(buf,sizeof(buf));
       if(recvfrom(cfd,buf,4,0,(struct sockaddr*)&addr,&len)<0)//接ACK
       {
           ERR_MSG("recvfrom");
           return -1;
       }
       if(htons(4)==*(unsigned short*)buf)
       {
           bzero(buf,sizeof(buf));
           *(unsigned short*)buf=htons(3);
           num++;
           *(unsigned short*)(buf+2) = htons(num);
           res=read(fd,buf+4,512);
           if(res<0)
           {
               ERR_MSG("read");
               return -1;
           }
           if(res==0)
           {
               printf("文件传输完毕\n");
               close(fd);
               break;
           }

           if(sendto(cfd,buf,(4+res),0,(struct sockaddr*)&addr,len)<0)
           {
               ERR_MSG("sendto");
               return -1;
           }
       }
       else if(htons(5)==*(unsigned short*)buf)
       {
           printf("------ERROR:%s------\n",buf+4);
           break;
       }
   }
   return 0;
}