linux poll 学习

一、poll介绍

函数原型：

#include <poll.h>
int poll(struct pollfd *fds, nfds_t nfds, int timeout);

struct pollfd定义：

struct pollfd {
   int   fd;         /* file descriptor */
   short events;     /* requested events */
   short revents;    /* returned events */
};

fd：文件描述符

events：关心的事件，输入参数

revents：产生的事件，输出参数

事件类型：

POLLIN    普通或优先级带数据可读
POLLRDNORM    普通数据可读
POLLRDBAND    优先级带数据可读
POLLPRI    高优先级数据可读
POLLOUT    普通数据可写
POLLWRNORM    普通数据可写
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

关于poll的具体用法，请见下面示例。

二、poll使用

示例1：回显服务器

/*******************************************************************************
* File Name        : poll.cpp
* Author        : zjw
* Email            : emp3XzA3MjJAMTYzLmNvbQo= (base64 encode)
* Create Time    : 2015年07月17日 星期五 09时42分11秒
*******************************************************************************/
#include <sys/types.h>
#include <sys/socket.h>
#include <poll.h>
#include <netinet/in.h>
#include <unistd.h>
#include <arpa/inet.h>

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cerrno>
#include <cstring>
using namespace std;

const int SERVER_PORT = ;
const int EVENT_SIZE = ;
const int RECV_SIZE = ;
const int SEND_SIZE = ;

int main(int argc, char **argv)
{
    int server = socket(AF_INET, SOCK_STREAM, );
    struct sockaddr_in addrServer;
    bzero(&addrServer, sizeof(addrServer));
    addrServer.sin_family = AF_INET;
    addrServer.sin_port = htons(SERVER_PORT);
    addrServer.sin_addr.s_addr = INADDR_ANY;

    if (bind(server, (struct sockaddr*)&addrServer, sizeof(addrServer)))
    {
        perror("bind failed,");
        return -;
    }

    listen(server, );
    cout << "listening on port:" << SERVER_PORT << " ..." << endl;

    struct pollfd fds[EVENT_SIZE] = {{, , }};
    fds[server].fd = server;
    fds[server].events = POLLIN;

    int ret = ;
    char recvBuf[RECV_SIZE + ];
    char sendBuf[SEND_SIZE + ];
    while ()
    {
        if ((ret = poll(fds, EVENT_SIZE, )) < )
        {
            perror("poll failed,");
            return -;
        }

        for (int i = ; i < EVENT_SIZE; i++)
        {
            if (fds[i].fd == )
            {
                continue;
            }

            if (fds[i].fd == server && (fds[i].revents & POLLIN))
            { // accept a new client
                struct sockaddr_in addrClient;
                socklen_t len = sizeof(addrClient);
                int client = accept(server, (struct sockaddr*)&addrClient, &len);
                if (client == -)
                {
                    perror("accept failed,");
                    return -;
                }
                else
                {
                    cout << "accep an new client " << client << ", ip:" << inet_ntoa(addrClient.sin_addr) << endl;
                    fds[client].fd = client;
                    fds[client].events = POLLIN;
                }
            }
            else if (fds[i].revents & POLLIN)
            { // read event
                memset(recvBuf, , RECV_SIZE + );
                if ((ret = recv(fds[i].fd, recvBuf, RECV_SIZE, )) < )
                {
                    perror("recv failed,");
                    return -;
                }
                else if (ret == )
                { // client close
                    close(fds[i].fd);
                    fds[i].fd = ;
                }
                else
                { // recv data
                    cout << "client " << fds[i].fd << " said:" << recvBuf << endl;
                    memset(sendBuf, , SEND_SIZE + );
                    sprintf(sendBuf, "You said:%s", recvBuf);
                    if ((ret = send(fds[i].fd, sendBuf, SEND_SIZE, )) < )
                    {
                        perror("send failed,");
                        return -;
                    }
                }
            }
            else
            { // write event

            }
        }
    }
    close(server);

    return ;
}

Makefile：

echo: poll.cpp
    g++ -g -o $@ $<

clean:
    rm -rf echo

运行结果：

服务器端：

客户端1：

客户端2：

三、参考

http://www.360doc.com/content/12/0821/10/7775902_231465100.shtml

http://blog.chinaunix.net/uid-23842323-id-2656589.html