socket编程热身程序

 /*server.c*/
 #include <stdio.h>
 #include <arpa/inet.h>
 #include <sys/types.h>          /* See NOTES */
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <stdlib.h>
 #include <unistd.h>
 #define  err_log(errlog) do{ perror(errlog); exit(1);}while(0)
 int main(int argc, const char *argv[])
 {
     int sockfd;
     int acceptfd;
     struct sockaddr_in  serveraddr, clientaddr;

16     if (argc != 3)
     {
         fprintf(stderr,"Usage:%s serverip port.\n", argv[]);
         return -;
     }
 /*server端 第一步：socket 创建套接字*/
     if((sockfd = socket(AF_INET, SOCK_STREAM, )) < )
     {
         err_log("fail to socket");
     }
    /*server端 第二步： 填充网络信息结构体*/
     serveraddr.sin_family = AF_INET;
     serveraddr.sin_addr.s_addr = inet_addr(argv[]);//argv[1]:由手动输入，终端的第二个参数
     serveraddr.sin_port = htons(atoi(argv[]));//htons 将本地字节序变为网络字节序，atoi将数字类字符串转化为数字，如字符串“80” 变为数字80
   /*server端 第三步 ：bind() 绑定*/
     if(bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < )
     {
         err_log("fail to bind");
     }
   /*server端 第四步：listen() 监听*/
     if(listen(sockfd, ) < )
     {
         err_log("fail to listen");
     }

     socklen_t  addrlen = sizeof(struct sockaddr_in);
         /*接收客户端的连接请求*/
     acceptfd = accept(sockfd, (struct sockaddr *)&clientaddr, &addrlen);

     if(acceptfd < )
     {
         err_log("fail to acceptfd");
     }

     printf("%s --> %d\n", inet_ntoa(clientaddr.sin_addr), ntohs(clientaddr.sin_port));
      /*inet_ntoa函数将网络字节序的IP地址转换为十进制的字符串*/
      /*ntohs 将网络端口号转换为本地端口号*/
     close(acceptfd); //关闭文件描述符
     close(sockfd);//关闭文件描述符

52     return ; 
    }

 /*client*/
 #include <stdio.h>
 #include <arpa/inet.h>
 #include <sys/types.h>          /* See NOTES */
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <stdlib.h>
 #include <unistd.h>
 #define  err_log(errlog) do{ perror(errlog); exit(1);}while(0)

 int main(int argc, const char *argv[])
 {
     int sockfd;
     int acceptfd;
     struct sockaddr_in  serveraddr, clientaddr;

     if(argc != )
     {
         fprintf(stderr,"Usage:%s serverip port.\n", argv[]);
         return -;
     }
     /*client端 第一步：socket套接字*/
     if((sockfd = socket(AF_INET, SOCK_STREAM, )) < )
     {
         err_log("fail to socket");
     }
    /*client端 第二部：填充网络信息结构体*/
     serveraddr.sin_family = AF_INET;
     serveraddr.sin_addr.s_addr = inet_addr(argv[]);
     serveraddr.sin_port = htons(atoi(argv[]));
    /*client端 第三步：连接服务器端*/
   if(connect(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < )
     {
         err_log("fail to connect");
     }
   close(sockfd);//关闭文件描述符
   return ;
 }