多路IO复用--poll实现

迷南。 2022-02-16 08:21 247阅读 0赞

### 文章目录 ###

*   *  函数参数说明
     *  server.c

## 函数参数说明 ##

int poll(struct pollfd *fds, nfds_t nfds, int timeout);
     struct pollfd {
        
                   int   fd;         /* file descriptor */
                   short events;     /* requested events */
                   short revents;    /* returned events */
               };
               
    Instructions on Linux: poll() performs a similar task to select(2): it waits for one of a set of file descriptors to become ready to perform I/O.
    	POLLIN			普通或带外优先数据可读,即POLLRDNORM | POLLRDBAND
    	POLLRDNORM		数据可读
    	POLLRDBAND		优先级带数据可读
    	POLLPRI 		高优先级可读数据
    	POLLOUT			普通或带外数据可写
    	POLLWRNORM		数据可写
    	POLLWRBAND		优先级带数据可写
    	POLLERR 		发生错误
    	POLLHUP 		发生挂起
    	POLLNVAL 		描述字不是一个打开的文件
    
    	nfds 			监控数组中有多少文件描述符需要被监控
    timeout 		毫秒级等待
    		-1：阻塞等，#define INFTIM -1 				Linux中没有定义此宏
    		=0：立即返回，不阻塞进程
    		>0：等待指定毫秒数，如当前系统时间精度不够毫秒，向上取值
    		
    如果不再监控某个文件描述符时，可以把pollfd中，fd设置为-1，poll不再监控此pollfd，下次返回时，把revents设置为0

## server.c ##

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <netinet/in.h>
    #include <arpa/inet.h>
    #include <poll.h>
    #include <errno.h>
    #define MAXLINE     80
    #define SERV_PORT   6666
    #define OPEN_MAX    1024
    
    int main(int argc, char *argv[])
    {
        
        int listenfd = 0;
        int connfd = 0;
        int sockfd = 0;
        int nready;
        char buf[MAXLINE],str[INET_ADDRSTRLEN];
        struct pollfd client[OPEN_MAX];
    
        listenfd = Socket(AF_INET,SOCK_STREAM,0);
        int opt = 1;
        setsockopt(listenfd,SOL_SOCKET,SO_REUSEADDR,&opt,sizeof(opt));
        struct sockaddr_in servaddr;
        bzero(&servaddr,sizeof(servaddr));
        servaddr.sin_family = AF_INET;
        servaddr.sin_port = htons(SERV_PORT);
        servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    
        Bind(listenfd,(struct sockaddr *)&servaddr,sizeof(servaddr));
        Listen(listenfd,128);
    
        memset(&client,-1,OPEN_MAX);//用-1初始化client[].fd里剩下元素
    
        client[0].fd = listenfd;
        client[0].events = POLLRDNORM;//listenfd 监听普通读事件
        int i = 0;
        nfds_t maxi = 0;   //client[]数组有效元素中最大元素下标
        for(;;)
        {
        
            nready = poll(client, maxi + 1, -1); //阻塞
            if(client[0].revents & POLLRDNORM)      //有客户端链接请求
            {
        
                struct sockaddr_in clienaddr;
                ssize_t cliensize = sizeof(clienaddr);
                bzero(&clienaddr,sizeof(clienaddr));
                connfd = Accept(listenfd,(struct sockaddr *)&clienaddr,&cliensize);
                strcpy(str,inet_ntop(AF_INET,&clienaddr.sin_addr,str,sizeof(str)));
                printf("received from %s at port %d\n",str,ntohs(clienaddr.sin_port));
                for(i = 1;i<OPEN_MAX;i++)
                {
        
                    if(client[i].fd < 0)
                    {
        
                        client[i].fd = connfd;//找到client[]中空闲的位置，存放accept返回的connfd
                        break;
                    }
                }
    
                if(i == OPEN_MAX)
                {
        
                    perr_exit("too many clients");
                }
                client[i].events = POLLRDNORM;      //设置刚刚返回的connfd，监控读事件
                if(i > maxi)
                {
        
                    maxi = i;
                }
                if(--nready <= 0)
                {
        
                    continue;
                }
            }
            for(i = 1; i <= maxi; i++)
            {
        
                sockfd = client[i].fd;
                if(sockfd < 0)
                {
        
                    continue;
                }
                short int flag = POLLRDNORM | POLLERR;
                printf("client[%d].revents = 0x%x,flag = 0x%x,revents&flag = 0x%x\n",i,
                       client[i].revents,flag,(client[i].revents)&flag);
                if(client[i].revents & (POLLRDNORM | POLLERR))
                {
        
                    printf("--------------------\n");
                    memset(buf,0,sizeof(buf));
                    ssize_t n = Read(sockfd,buf,MAXLINE);
                    if(n < 0)
                    {
        
                        if(errno == ECONNRESET) //当收到 RST标志时
                        {
        
                            printf("client[%d] aborted connection\n",i);
                            Close(sockfd);
                            client[i].fd = -1;
                        }
                        else
                        {
        
                            perr_exit("read error");
                        }
                    }
                    else if(n == 0)
                    {
        
                        printf("client[%d] closed connection\n",i);
                        Close(sockfd);
                        client[i].fd = -1;
                    }
                    else
                    {
        
                        struct sockaddr_in sa;
                        int len = sizeof(sa);
                        if(!getpeername(sockfd, (struct sockaddr *)&sa, &len))
                        {
        
                            printf( "%s :%d-->%s\n", inet_ntoa(sa.sin_addr),ntohs(sa.sin_port),buf);
                        }
                        Write(sockfd,buf,n);//回射客户端
                    }
                    if(--nready <= 0)
                    {
        
                        break;
                    }
                }
            }
        }
        return 0;
    }