（转）Linux中select函数学习及实例笔记（二）

原文地址：http://www.cnblogs.com/luoxn28/p/6220372.html

#include <iostream>
#include <vector>

#include <unistd.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>

using namespace std;

int getMaxNumOfVector(vector<int> &fds);
vector<int> flipVector(vector<int> &fds);

int main(int argc, char **argv)
{
    vector<int> fds;
    int listenfd, connfd;
    struct sockaddr_in servaddr;
    
    listenfd = socket(AF_INET, SOCK_STREAM, 0);
    
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(8080);
    servaddr.sin_addr.s_addr = INADDR_ANY;
    
    bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
    listen(listenfd, 5);
    
    fd_set read_fd;
    fd_set write_fd;
    fd_set except_fd;
    char buff[1024];
    
    FD_ZERO(&read_fd);
    FD_ZERO(&write_fd);
    FD_ZERO(&except_fd);
    
    fds.push_back(STDIN_FILENO);
    fds.push_back(listenfd);
    
    bool running = true;
    while (running) {
        buff[0] = '\0';
        
        /**
         * 每次调用select都要重新初始化read_fd和except_fd中的文件描述符集
         */
        for (int i = 0; i < fds.size(); i++) {
            FD_SET(fds[i], &read_fd);
            if ((fds[i] != STDIN_FILENO) && (fds[i] != listenfd)) {
                //FD_SET(fds[i], &write_fd);
                FD_SET(fds[i], &except_fd);
            }
        }
        
        int event_num = select(getMaxNumOfVector(fds) + 1, &read_fd, &write_fd, &except_fd, NULL);
        if (event_num < 0) {
            cerr << "select error" << endl;
            break;
        }
        
        for (int i = 0; i < fds.size(); i++) {
            if (fds[i] == STDIN_FILENO) {
                // 从STDIN_FILENO中读取数据
                if (FD_ISSET(STDIN_FILENO, &read_fd)) {
                    cin >> buff;
                    if (strcmp(buff, "quit") == 0) {
                        running = false;
                        break;
                    }
                    else {
                        cout << buff << endl;
                    }
                }
            }
            else if (fds[i] == listenfd) {
                if (FD_ISSET(listenfd, &read_fd)) {
                    connfd = accept(listenfd, NULL, NULL);
                    if (connfd < 0) {
                        running = false;
                        break;
                    }
                    
                    fds.push_back(connfd);
                    cout << "往fds添加 " << connfd << ", fds.size: " << fds.size() << endl;
                }
            }
            else {
                if (FD_ISSET(fds[i], &read_fd)) {
                    int len = recv(fds[i], buff, sizeof(buff) - 1, 0);
                    if (len < 0) {
                        cerr << "recv error" << endl;
                    }
                    else if (len == 0) {
                        cout << "从fds删除 " << fds[i] << endl;
                        // 客户端断开了连接
                        fds[i] = -1;
                    }
                    else {
                        buff[len] = '\0';
                        cout << fds[i] << " recv: " << buff << endl;
                    }
                }
                else if (FD_ISSET(fds[i], &write_fd)) {
                    
                }
                else if (FD_ISSET(fds[i], &except_fd)) {
                    
                }
            }
        }
        
        fds = flipVector(fds);
    }
    
    // 关闭文件描述符
    for (int i = 0; i < fds.size(); i++) {
        close(fds[i]);
    }
    close(listenfd);

    return 0;
}

int getMaxNumOfVector(vector<int> &fds)
{
    int result = 0;
    
    for (int i = 0; i < fds.size(); i++) {
        if (fds[i] > result) {
            result = fds[i];
        }
    }
    
    return result;
}

vector<int> flipVector(vector<int> &fds) {
    vector<int> fdsnew;
    
    for (int i = 0; i < fds.size(); i++) {
        if (fds[i] != -1) {
            fdsnew.push_back(fds[i]);
        }
    }
    
    return fdsnew;
}