学步园

下面是一个简单的时间服务器程序。

#include <stdio.h>  
#include <stdlib.h>  
#include <unistd.h>
#include <string.h>  
#include <sys/types.h>  
#include <sys/socket.h>
#include <time.h>
#include <netinet/in.h>  
#include <arpa/inet.h>  
 
#define MAX_LISTEN             5  
#define PORT                 1234  
 
int main()  
{  
    int conn_fd = 0;  
    int sock_fd = 0;
    int recv_num;  
    int send_num;  
    char recv_buf[100];  
    char send_buf[100];   
    int i, ready, max_fd;
    fd_set readset;  
    int client[FD_SETSIZE];              //用一个数组记录描述符的状态
    struct sockaddr_in addr_client;  
    struct sockaddr_in addr_serv;  
    socklen_t client_size;

    //创建socket
    sock_fd = socket(AF_INET,SOCK_STREAM,0);  
    if (sock_fd < 0)
    {  
        printf("create socket failed\n");  
        return -1;  
    }  

    client_size = sizeof(struct sockaddr_in);  

    //设置套接口
    int opt = SO_REUSEADDR;
    setsockopt(sock_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

    memset(&addr_serv, 0, sizeof(addr_serv));  
    addr_serv.sin_family = AF_INET;  
    addr_serv.sin_port = htons(PORT);  
    addr_serv.sin_addr.s_addr = htonl(INADDR_ANY);  

    //为创建的socket绑定端口
    if (bind(sock_fd, (struct sockaddr *)&addr_serv, sizeof(struct sockaddr_in)) < 0)
    {   
        printf("bind error\n");  
        return -1;  
    }  

    if (listen(sock_fd, MAX_LISTEN) < 0)
    {  
        printf("listen error\n");  
        return -1;
    }  

    //初始化套接字数组
    for (i=0; i<FD_SETSIZE; i++)
    {  
        client[i] = -1;  
    }  
    
    max_fd = sock_fd;  
    while (1)
    {  
        //重置监听的描述符  
        FD_ZERO(&readset);  
        FD_SET(sock_fd, &readset);  
        for (i=0; i<FD_SETSIZE; i++)
        {  
            if (client[i] == 1)
            {  
                FD_SET(i, &readset);  
            }  
        }  

        //开始监听描述符，是异步的，不会阻塞  
        ready = select(max_fd+1, &readset, NULL, NULL, NULL);  

        //判断是否有可用套接字
        if (FD_ISSET(sock_fd, &readset))
        {  
            conn_fd = accept(sock_fd, (struct sockaddr *)&addr_client, &client_size);  
            if (conn_fd < 0)
            {  
                printf("accept error\n");  
                return -1;
            }  

            //将新建连接的套接字添加到的select序列
            FD_SET(conn_fd, &readset);          
            //从readset序列清除sockfd
            FD_CLR(sock_fd, &readset);          

            if (conn_fd > max_fd)
            {  
                max_fd = conn_fd;  
            }  
            client[conn_fd] = 1;      
        }  

        //检查所有的描述符，判断是否有可用套接字，有的话对套接字进行读写操作
        for (i=0; i<FD_SETSIZE; i++)
        {  
            if (FD_ISSET(i, &readset))
            {  
                recv_num = recv(i, recv_buf, sizeof(recv_buf), 0);  
                if (recv_num <= 0)
                {  
                    //从readset序列清除i套接字
                    FD_CLR(i, &readset);          
                    client[i] = -1;  
                }  
                recv_buf[recv_num] = '\0';  

                //获取时间
                memset(send_buf, 0, sizeof(send_buf));  
                struct tm * timeinfo;
                time_t gttime;
                time(>time);
                timeinfo = localtime(>time);
                char sTime[20];
                sprintf(sTime,"%4d-%02d-%02d %02d:%02d:%02d"
                    ,1900+timeinfo->tm_year, 1+timeinfo->tm_mon,timeinfo->tm_mday
                    ,timeinfo->tm_hour,timeinfo->tm_min,timeinfo->tm_sec);

                //给客户度端发送时间
                send_num = send(i, sTime, strlen(sTime), 0);
                if (send_num <= 0)
                {  
                    FD_CLR(i, &readset);  
                    client[i] = -1;  
                }  
            }  
        }  
    }  

    close(sock_fd);  
    
    return 0;  
}