网络编程学习之路3-epoll

书接前文，前文书讲到使用多线程来处理tcp 连接，这次是使用单线程+epoll来处理tcp连接。
使用多线程来管理tcp连接，会增加多线程创建所代码的开销。系统所能接受的tcp连接数 = 系统内存/线程栈大小。我用的ubuntu默认栈大小是8M。1G的空间也只能创建128个tcp连接。当然可以通过增加内存或者调整栈空间大小来让单机接收更多连接。但始终不是一种高效的办法。

epoll api

//创建epoll实例
extern int epoll_create (int __size) ;
//用来增加或移除被epoll所监听的文件描述符
int epoll_ctl(int epfd, int op, int fd, struct 	epoll_event *event);
//等待epoll实例中注册的事件触发,timeout =-1表示无限等待
 int epoll_wait(int epfd, struct epoll_event* events, int maxevents, int timeout);

效果

同样是用telnet来测试，server端打印如下

[email protected]:~/share/mycode/c++/tcp-server-epoll$ ./bin/Debug/tcp-server-epoll 
socket fd is 3
local ip =0.0.0.0
enter epoll_wait
epoll -wait end ,active_fd_num =1
accept connect success, client port=13475ip =127.0.0.1
newsockfd=5
enter epoll_wait
epoll -wait end ,active_fd_num =1
accept connect success, client port=14499ip =127.0.0.1
newsockfd=6
enter epoll_wait
epoll -wait end ,active_fd_num =1
accept connect success, client port=15011ip =127.0.0.1
newsockfd=7
enter epoll_wait
epoll -wait end ,active_fd_num =1
------------------------sockfd 5 start----------------
thread: 15156 sockfd:5 recv data:fdjaidf
------------------------sockfd  5 end----------------
enter epoll_wait
epoll -wait end ,active_fd_num =1
------------------------sockfd 5 start----------------
thread: 15156 sockfd:5 recv data:

------------------------sockfd  5 end----------------
enter epoll_wait
epoll -wait end ,active_fd_num =1
------------------------sockfd 6 start----------------
thread: 15156 sockfd:6 recv data:faifda

------------------------sockfd  6 end----------------
enter epoll_wait
epoll -wait end ,active_fd_num =1
------------------------sockfd 7 start----------------
thread: 15156 sockfd:7 recv data:fjiadfa
------------------------sockfd  7 end----------------
enter epoll_wait
epoll -wait end ,active_fd_num =1
------------------------sockfd 7 start----------------
thread: 15156 sockfd:7 recv data:

------------------------sockfd  7 end----------------
enter epoll_wait

代码

#include <iostream>
#include <arpa/inet.h>
#include <err.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <thread>
#include <sys/epoll.h>

#define PORT 12351
#define  MAXSIZE 10240
#define MAX_EVENT 100

using namespace std;


void read_data(int sockfd){
    printf("------------------------sockfd %d start----------------\n", sockfd);
    long tid = getpid();

    char *buffer = (char*)malloc( 1000 * sizeof(char));
    int n = read(sockfd, (void*)buffer, sizeof(buffer)/sizeof(char));
    if(n ==-1){
        perror("read error");
        strerror(errno);
        std::cout<<"socket fd =" << sockfd<<std::endl;
        free(buffer);
        exit(errno);
    }
        std::cout<< "thread: "<<tid << " sockfd:"<<sockfd<<" recv data:" <<string(buffer,n)<<std::endl;

     free(buffer);
     printf("------------------------sockfd  %d end----------------\n", sockfd);
}

int main(int args, char *argv[])
{
//    cout << "Hello world!" << endl;
    int sockfd, newsockfd;
    struct sockaddr_in server_addr;
    struct sockaddr_in client_addr;

    int sin_size, portnum;
    char buf[MAX_EVENT][MAXSIZE] = {0};

    int epfd ;
    int active_fd_num;

    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
        fprintf(stderr, "create socket failed!");
        strerror(errno);
        close(sockfd);
        exit(1);
    }

    std::cout<<"socket fd is " << sockfd <<std::endl;

    bzero(&server_addr, sizeof(struct sockaddr_in));
    server_addr.sin_port = htons(PORT);
    server_addr.sin_family = AF_INET;
//    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_addr.s_addr = inet_addr("0.0.0.0");

    if( bind(sockfd, (struct sockaddr*)(&server_addr), sizeof(struct sockaddr))){
        fprintf(stderr, "bind failed");
        strerror(errno);
        close(sockfd);
        exit(2);
    }

    struct sockaddr_in local_addr;
    int len;
    if (getsockname(sockfd, (struct sockaddr *)&local_addr, (socklen_t* )&len) == 0) {
        struct sockaddr_in* sin = (struct sockaddr_in*)(&local_addr);
//        *port = sin->sin_port;
        char addr_buffer[INET_ADDRSTRLEN];
        void * tmp = &(sin->sin_addr);
        if (inet_ntop(AF_INET, tmp, addr_buffer, INET_ADDRSTRLEN) == NULL){
         cerr << "inet_ntop err";
         return false;
        }
        printf("local ip =%s\n", addr_buffer);
    }

    if(listen(sockfd, 10) < 0){
        fprintf(stderr,"listen failed");
        strerror(errno);
        close(sockfd);
        exit(3);
    }
    sin_size = sizeof(struct sockaddr_in);

    //create epoll fd
    if((epfd = epoll_create(100)) == -1){
        fprintf(stderr, "create epoll fd failed!");
        strerror(errno);
        close(epfd);
        exit(1);
    }
    struct epoll_event ev, active_events[100];
    ev.data.fd = sockfd;
    ev.events = EPOLLIN;

    if(epoll_ctl(epfd, EPOLL_CTL_ADD, sockfd,  &ev) == -1){
        fprintf(stderr, "add sock fd failed!");
        strerror(errno);
        close(epfd);
        exit(1);
    }
    while(1){
        std::cout<<"enter epoll_wait" <<std::endl;
        active_fd_num = epoll_wait(epfd, active_events, MAX_EVENT, -1);//-1
        if(active_fd_num <= 0)
            continue;
        std::cout<<"epoll -wait end ,active_fd_num =" << active_fd_num<<std::endl;

        for(int i =0; i<active_fd_num ; i++){
            if(active_events[i].data.fd == sockfd){
                if( (newsockfd = accept(sockfd, (struct sockaddr *) (&client_addr),(socklen_t*) &sin_size))< 0){
                    fprintf(stderr, "listen failed");
                    strerror(errno);
                    exit(3);
                }
                std::cout<<"accept connect success, client port=" << client_addr.sin_port<<
                "ip =" <<inet_ntoa(client_addr.sin_addr)<<std::endl;
                std::cout<< "newsockfd=" << newsockfd<<std::endl;

                 active_events[i].events = EPOLLIN;
                 active_events[i].data.fd = newsockfd;
                 if(epoll_ctl(epfd, EPOLL_CTL_ADD, newsockfd,  &active_events[i]) == -1){
                        fprintf(stderr, "add sock fd failed!");
                        strerror(errno);
                        close(epfd);
                        exit(1);
                 }

            }else {
                read_data(active_events[i].data.fd);
            }
        }
    }
    for(int i =0; i<MAX_EVENT ;i++){
        if( active_events[i].data.fd != 0)
            close(active_events[i].data.fd);
    }

    return 0;
}