poll实现多路IO

源码地址：https://github.com/whuwzp/linuxc/tree/master/poll
源码说明：
- server.cpp: 监听127.1:6666，功能是将收到的小写转大写
- include/wrap.cpp: 封装的一些socket基本操作，加了基本的错误处理

1. 概要

一定先select实现,poll是select的改进版:,有以下不同

输入输出参数方面
- select: 需要allfds和readfds两个集合,因为readfds作为输入输出参数,每次select前都要用allfds赋值给它
- poll: pollfd结构体中,有events和revents两个,分别用来表示输入输出
监听集合的形式
- select: 用fd_set位图标记需要监听的fd
- poll: 用pollfd结构体中的fd成员标记,用结构体数组表示需要监听的集合
监听信号类型
- select: 用readfds, writefds集合分别表示
- poll: 用POLLIN,POLLOUT表示,fds[0].events = POLLIN
判断是否有信号
- select: 用FD_ISSET(fd,readfds)
- poll: 用fds[0].revents & POLLIN

2. 核心代码

#include "include/wrap.h"

#include <arpa/inet.h>

#include <ctype.h>

#include <errno.h>

#include <netinet/in.h>

#include <poll.h>

#include <pthread.h>

#include <stdio.h>

#include <stdlib.h>

#include <stdnoreturn.h>

#include <string.h>

#include <sys/select.h>

#include <sys/socket.h>

#include <sys/types.h> /* See NOTES */

#include <unistd.h>

#include <wait.h>

#define LOCALIP "127.0.0.1"

#define PORT 6666

void handler(char *in, char *out) {

    for (int i = 0; i < (int)strlen(out) + 1; ++i) {

        out[i] = toupper(in[i]);

    }

}

int workthread(const int &fd_client) {

    char recvbuf[2048] = {0};

    char sendbuf[2048] = {0};

    int  ret           = 0;

    ret = (int)Read(fd_client, recvbuf, 2048);

    if (ret <= 0) {

        printf("ret==0\n");

        return ret;

    }

    handler(recvbuf, sendbuf);

    ret = (int)Write(fd_client, sendbuf, strlen(sendbuf) + 1);

    return ret;

}

void startsock(int &fd, struct sockaddr_in &addr, const char *ip,

               const int port) {

    fd = Socket(AF_INET, SOCK_STREAM, 0);

    memset(&addr, 0, sizeof(addr));

    addr.sin_family      = AF_INET;

    addr.sin_addr.s_addr = inet_addr(ip);

    addr.sin_port        = htons(port);

}

int main() {

    int                fd_server = 0;

    int                fd_client = 0;

    int                ret       = 0;

    struct sockaddr_in sock_client;

    struct sockaddr_in sock_server;

    socklen_t          client_len = (socklen_t)sizeof(sock_client);

    int                opt        = 0;

    struct pollfd      fds[FD_SETSIZE];

    int                maxi    = 0;

    int                nselect = 0;

    int                i       = 0;

    startsock(fd_server, sock_server, LOCALIP, PORT);

    opt = 1;

    Setsockopt(fd_server, SOL_SOCKET, SO_REUSEADDR, &opt,

               (socklen_t)sizeof(opt));

    Bind(fd_server, (struct sockaddr *)&sock_server, sizeof(sock_server));

    Listen(fd_server, 5);

    for (i = 0; i < FD_SETSIZE; ++i) {

        fds[i].fd     = -1;

        fds[i].events = POLLIN;

    }

    fds[0].fd = fd_server;

    maxi   = 0;

	while (true) {

        printf("polling...\n");

        nselect = poll(fds, (unsigned long)maxi+1, -1);

        if (nselect == -1) {

            if (errno == EINTR) {

                continue;

            } else {

                perror_exit("poll failed");

            }

        }

        printf("get %d select\n", nselect);

        if (fds[0].revents & POLLIN) {

            fd_client =

                Accept(fd_server, (struct sockaddr *)&sock_client, &client_len);

            printf("accept: %s: %d\n", inet_ntoa(sock_client.sin_addr),

                   ntohs(sock_client.sin_port));

            for (i = 0; i < FD_SETSIZE; ++i) {

                if (fds[i].fd != -1) continue;

                fds[i].fd = fd_client;

                break;

            }

            printf("i: %d, FD_SETSIZE: %d\n", i, FD_SETSIZE);

            if (i == FD_SETSIZE) perror_exit("too many clients");

            if (i > maxi) maxi = i;

            nselect--;

        }

        printf("going to find client, maxi: %d, nselect: %d\n", maxi, nselect);

        for (i = 0; (i <= maxi) && (nselect > 0); ++i) {

            if (!( fds[i].revents & POLLIN )) continue;

            printf("find client %d\n", i + 1);

            ret = workthread(fds[i].fd);

            if (ret <= 0) {

                Close(fds[i].fd);

                fds[i].fd = -1;

            }

            nselect--;

        }

        sleep(3);

    }

    Close(fd_server);

    for (i = 0; i < FD_SETSIZE; ++i) {

        if (fds[i].fd == -1) continue;

        Close(fds[i].fd);

    }

}

3. 参考网址

https://www.bilibili.com/video/av53016117

巴特西

Linux C++ 网络编程学习系列（3）——多路IO之poll实现

poll实现多路IO

1. 概要

2. 核心代码

3. 参考网址

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