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epoll的使用例子

 // local.h
#include <iostream>
#include <list>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <sys/epoll.h>
#include <sys/sendfile.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <fcntl.h>
#include <errno.h> 




#define BUF_SIZE 1024                 //預設緩沖區
#define SERVER_PORT 44444             //監聽端口
#define SERVER_HOST "192.168.1.103"   //伺服器IP位址
#define EPOLL_RUN_TIMEOUT -1          //epoll的逾時時間
//#define EPOLL_SIZE 10000              //epoll監聽的用戶端的最大數目
#define EPOLL_SIZE 1019              //epoll監聽的用戶端的最大數目

#define STR_WELCOME "Welcome to seChat! You ID is: Client #%d"
#define STR_MESSAGE "Client #%d>> %s"
#define STR_NOONE_CONNECTED "Noone connected to server except you!"
#define CMD_EXIT "EXIT"

//兩個有用的宏定義：檢查和指派并且檢測
#define CHK(eval) if(eval < 0){perror("eval"); exit(-1);}
#define CHK2(res, eval) if((res = eval) < 0){perror("eval"); exit(-1);}

//================================================================================================
//函數名：                  setnonblocking
//函數描述：                設定socket為不阻塞
//輸入：                    [in] sockfd socket标示符
//輸出：                    無
//傳回：                    0
//================================================================================================
int setnonblocking(int sockfd);

//================================================================================================
//函數名：                  handle_message
//函數描述：                處理每個用戶端socket
//輸入：                    [in] new_fd socket标示符
//輸出：                    無
//傳回：                    傳回從用戶端接受的資料的長度
//================================================================================================
int handle_message(int new_fd);
           
// utils.h 

#include "local.h"


int setnonblocking(int sockfd)
{
    CHK(fcntl(sockfd, F_SETFL, fcntl(sockfd, F_GETFD, 0)|O_NONBLOCK));
    return 0;
}

server.cpp

生成server  g++ -o server server.cpp

#include "local.h"
#include "utils.h"

using namespace std;

list<int>clients_list;

int main(int ac,char**av)
{
    int listenfd;
    struct sockaddr_in addr,their_addr;
    addr.sin_family=AF_INET;
    addr.sin_port=htons(SERVER_PORT);
    addr.sin_addr.s_addr=inet_addr(SERVER_HOST);
    socklen_t socklen;
    socklen=sizeof(struct sockaddr_in);


    static struct epoll_event ev,events[EPOLL_SIZE];
    char message[BUF_SIZE];
    int epfd;
    clock_t tStart;

    int client,res,epoll_events_count;

    CHK2(listenfd,socket(AF_INET,SOCK_STREAM,0));
    setnonblocking(listenfd);
    CHK(bind(listenfd,(struct sockaddr*)&addr,sizeof(addr)));
    CHK(listen(listenfd,1));

    CHK2(epfd,epoll_create(EPOLL_SIZE));
    ev.events=EPOLLIN;
    ev.data.fd=listenfd;
    CHK(epoll_ctl(epfd,EPOLL_CTL_ADD,listenfd,&ev));

    while(1){
	CHK2(epoll_events_count,epoll_wait(epfd,events,EPOLL_SIZE,
		    EPOLL_RUN_TIMEOUT));
	tStart=clock();
	for(int i=0;i<epoll_events_count;i++){
	    if(events[i].data.fd==listenfd){
		CHK2(client,accept(listenfd,(struct sockaddr*)&their_addr,
			    &socklen));
		setnonblocking(client);
		ev.data.fd=client;
		CHK(epoll_ctl(epfd,EPOLL_CTL_ADD,client,&ev)); //沒有改變事件，依然是
								//沿用的ev.events
								//=EPOLL_IN,可讀事件
               //這裡的ev起到一個綁定事件和描述符的中間變量，可以重複使用
	       //也即，每個描述符都可以綁定特殊的事件
		clients_list.push_back(client);
		bzero(message,BUF_SIZE);
		res=sprintf(message,STR_WELCOME,client);
		CHK2(res,send(client,message,BUF_SIZE,0));
	    }else{
		CHK2(res,handle_message(events[i].data.fd));
	    }
	}
	printf("statistics:%d events handled spent:%.2f second \n",
		epoll_events_count,(double)(clock()-tStart)/CLOCKS_PER_SEC);
    }

    close(listenfd);
    close(epfd);
    return 0;
}
int handle_message(int client)
{
    char buf[BUF_SIZE],message[BUF_SIZE];
    bzero(buf,sizeof(buf));
    bzero(message,sizeof(message));

    int len;
    CHK2(len,recv(client,buf,BUF_SIZE,0));

    if(len==0){ //表示收到了FIN分節
	CHK(close(client));
	clients_list.remove(client);
    }else{
	if(clients_list.size()==1){
	    CHK(send(client,STR_NOONE_CONNECTED,strlen(STR_NOONE_CONNECTED),
			0));
	    return len;
	}
	sprintf(message,STR_MESSAGE,client,buf);
	list<int>::iterator it; //模仿了群聊，轉發給所有人
	for(it=clients_list.begin();it!=clients_list.end();it++){
	    if(*it!=client)
		CHK(send(*it,message,BUF_SIZE,0));
	}
    }
    return len;
}

 test.cpp 模拟高并發，連接配接成功後，函數就傳回了，所有連接配接又斷裂

g++ -o test test.cpp

#include "local.h"
#include "utils.h"

using namespace std;

char message[BUF_SIZE];
list<int>list_of_clients;
int res;
clock_t tStart;

int main(int ac,char**av)
{
    int sock;
    struct sockaddr_in addr;
    addr.sin_family=AF_INET;
    addr.sin_port=htons(SERVER_PORT);
    addr.sin_addr.s_addr=inet_addr(SERVER_HOST);

    tStart=clock();
    for(int i=0;i<EPOLL_SIZE;i++){
	CHK2(sock,socket(PF_INET,SOCK_STREAM,0));
	CHK(connect(sock,(struct sockaddr*)&addr,sizeof(addr))<0);
	list_of_clients.push_back(sock);

	bzero(&message,BUF_SIZE);
	CHK2(res,recv(sock,message,BUF_SIZE,0));
	printf("%s\n",message);
    }

    list<int>::iterator it;
    for(it=list_of_clients.begin();it!=list_of_clients.end();it++)
	close(*it);
    printf("Test passed at:%.4f second(s)\n",
	    (double)(clock()-tStart)/CLOCKS_PER_SEC);
    printf("Total server connections was:%d\n",EPOLL_SIZE);
    return 0;
}

client.cpp

可以試着群聊：：：

#include "local.h"
#include "utils.h"

using namespace std;

char message[BUF_SIZE];

/*
    流程：
        調用fork産生兩個程序，兩個程序通過管道進行通信
        子程序：等待客戶輸入，并将客戶輸入的資訊通過管道寫給父程序
        父程序：接受伺服器的資訊并顯示，将從子程序接受到的資訊發送給伺服器
*/
int main(int argc, char *argv[])
{
    int sock, pid, pipe_fd[2], epfd;

    struct sockaddr_in addr;
    addr.sin_family = PF_INET;
    addr.sin_port = htons(SERVER_PORT);
    addr.sin_addr.s_addr = inet_addr(SERVER_HOST);

    static struct epoll_event ev, events[2]; 
    ev.events = EPOLLIN | EPOLLET;

    //退出标志
    int continue_to_work = 1;

    CHK2(sock,socket(PF_INET, SOCK_STREAM, 0));
    CHK(connect(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0);

    CHK(pipe(pipe_fd));
    
    CHK2(epfd,epoll_create(EPOLL_SIZE));

    ev.data.fd = sock;
    CHK(epoll_ctl(epfd, EPOLL_CTL_ADD, sock, &ev));

    ev.data.fd = pipe_fd[0];
    CHK(epoll_ctl(epfd, EPOLL_CTL_ADD, pipe_fd[0], &ev));

    // 調用fork産生兩個程序
    CHK2(pid,fork());
    switch(pid)
    {
        case 0:                   // 子程序
            close(pipe_fd[0]);    // 關閉讀端
            printf("Enter 'exit' to exit\n");
            while(continue_to_work)
            {
                bzero(&message, BUF_SIZE);
                fgets(message, BUF_SIZE, stdin);

                // 當收到exit指令時，退出
                if(strncasecmp(message, CMD_EXIT, strlen(CMD_EXIT)) == 0)
                {
                    continue_to_work = 0;
                }
                else
                {            
                    CHK(write(pipe_fd[1], message, strlen(message) - 1));
                }
            }
            break;
        default:                 // 父程序
            close(pipe_fd[1]);   // 關閉寫端
            int epoll_events_count, res;
            while(continue_to_work) 
            {
                CHK2(epoll_events_count,epoll_wait(epfd, events, 2, EPOLL_RUN_TIMEOUT));

                for(int i = 0; i < epoll_events_count ; i++)
                {
                    bzero(&message, BUF_SIZE);
                    if(events[i].data.fd == sock)   //從伺服器接受資訊
                    {
                        CHK2(res,recv(sock, message, BUF_SIZE, 0));
                        if(res == 0)               //伺服器已關閉
                        {
                            CHK(close(sock));
                            continue_to_work = 0;
                        }
                        else 
                        {
                            printf("%s\n", message);
                        }
                    }
                    else        //從子程序接受資訊
                    {
                        CHK2(res, read(events[i].data.fd, message, BUF_SIZE));
                        if(res == 0)
                        {
                            continue_to_work = 0; 
                        }
                        else
                        {
                            CHK(send(sock, message, BUF_SIZE, 0));
                        }
                    }
                }
            }
    }
    if(pid)
    {
        close(pipe_fd[0]);
        close(sock);
    }else
    {
        close(pipe_fd[1]);
    }

    return 0;
}
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