网络编程 day2-优快云博客

本文链接：https://blog.youkuaiyun.com/zero2all/article/details/131119426

该程序创建了一个UDP套接字，绑定到指定端口，接收用户输入的文件名，向服务器发送请求。如果收到允许打开文件的响应，程序打开并写入接收到的数据，然后发送确认消息。

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#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/msg.h>
#include<stdio.h>
#include<sys/ipc.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<sys/stat.h>
#include<fcntl.h>
#define PORT 69
#define IP "192.168.2.144"
#define ERR_MSG(msg) do{\
   fprintf(stderr,"line:%d: %s %s",__LINE__,__FILE__,__func__);\
   perror(msg);\
}while(0)
int main()
{

   //创建套接字
   int soketfd=socket(AF_INET,SOCK_DGRAM,0);
   if(soketfd<0)
   {
       ERR_MSG("socket");
       return -1;
   }
   struct sockaddr_in myaddr;
   myaddr.sin_family=AF_INET;
   myaddr.sin_port=htons(PORT);
   myaddr.sin_addr.s_addr=inet_addr(IP);
   //绑定端口与套字节
   if(bind(soketfd,(struct sockaddr *)&myaddr,sizeof(myaddr))<0)
   {
       ERR_MSG("bind");
       return -1;
   }
   printf("bind success __%d__\n",__LINE__);
   char buf[516]="";
   char *sp1;
   short blok;
   printf("input the filename\n");
   scanf("%s",sp1);
   int size=sprintf(buf,"%c%c%s%c%s%c",0,1,sp1,0,"octet",0);
   if(sendto(soketfd,buf,size,0,(struct sockaddr *)&myaddr,size)<0)
   {
       ERR_MSG("SENDTO");
       return -1;
   }
   printf("send access __%d__",__LINE__);

   struct sockaddr_in cin;
   int addrlen=sizeof(cin);
   int myopen;
   if(recvfrom(soketfd,buf,size,0,(struct sockaddr *)&cin,&addrlen)<0)
   {
       ERR_MSG("RECSFROM");
       return -1;
   }
   if(buf[2]==5)
   {
       char *sp2=buf+4;
       printf("%s\n",sp2);
   }
   else if(buf[2]==3)
   {
       if(myopen==open("./test.txt",O_RDWR|O_APPEND|O_CREAT,0664))
       {
           ERR_MSG("OPEN");
           return -1;
       }
       while(buf)
       {
           write(myopen,buf,strlen(buf));
       }
       buf[0]=4;
       char ack[4];
       sprintf(ack,"%c%c%s",0,4,buf[2]);
       if(sendto(ack,buf,4,0,(struct sockaddr_in *)&cin,sizeof(cin))<0)
       {
           ERR_MSG("SENDTO");
           return -1;
       }
       close(myopen);
   }

   close(soketfd);
   return 0;
}