select实现高并发服务器

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <ctype.h>

#include "wrap.h"

#define SERV_PORT 6666

int main(int argc, char *argv[])
{
    int i, j, n, maxi;

    int nready, client[FD_SETSIZE];                 /* 自定义数组client, 防止遍历1024个文件描述符  FD_SETSIZE默认为1024 */
    int maxfd, listenfd, connfd, sockfd;
    char buf[BUFSIZ], str[INET_ADDRSTRLEN];         /* #define INET_ADDRSTRLEN 16 */

    struct sockaddr_in clie_addr, serv_addr;
    socklen_t clie_addr_len;
    fd_set rset, allset;                            /* rset 读事件文件描述符集合 allset用来暂存 */

    listenfd = Socket(AF_INET, SOCK_STREAM, 0);

    int opt = 1;
    setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

    bzero(&serv_addr, sizeof(serv_addr));
    serv_addr.sin_family= AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port= htons(SERV_PORT);

    Bind(listenfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr));
    Listen(listenfd, 128);

    maxfd = listenfd;                                           /* 起初 listenfd 即为最大文件描述符 */

    maxi = -1;                                                  /* 将来用作client[]的下标, 初始值指向0个元素之前下标位置 */
    for (i = 0; i < FD_SETSIZE; i++)
        client[i] = -1;                                         /* 用-1初始化client[] */

    FD_ZERO(&allset);
    FD_SET(listenfd, &allset);                                  /* 构造select监控文件描述符集 */

    while (1) {   
        rset = allset;                                          /* 每次循环时都从新设置select监控信号集 */
        nready = select(maxfd+1, &rset, NULL, NULL, NULL);
        if (nready < 0)
            perr_exit("select error");

        if (FD_ISSET(listenfd, &rset)) {                        /* 说明有新的客户端链接请求 */

            clie_addr_len = sizeof(clie_addr);
            connfd = Accept(listenfd, (struct sockaddr *)&clie_addr, &clie_addr_len);       /* Accept 不会阻塞 */
            printf("received from %s at PORT %d\n",
                    inet_ntop(AF_INET, &clie_addr.sin_addr, str, sizeof(str)),
                    ntohs(clie_addr.sin_port));

            for (i = 0; i < FD_SETSIZE; i++)
                if (client[i] < 0) {                            /* 找client[]中没有使用的位置 */
                    client[i] = connfd;                         /* 保存accept返回的文件描述符到client[]里 */
                    break;
                }

            if (i == FD_SETSIZE) {                              /* 达到select能监控的文件个数上限 1024 */
                fputs("too many clients\n", stderr);
                exit(1);
            }

            FD_SET(connfd, &allset);                            /* 向监控文件描述符集合allset添加新的文件描述符connfd */
            if (connfd > maxfd)
                maxfd = connfd;                                 /* select第一个参数需要 */

            if (i > maxi)
                maxi = i;                                       /* 保证maxi存的总是client[]最后一个元素下标 */

            if (--nready == 0)
                continue;
        } 

        for (i = 0; i <= maxi; i++) {                               /* 检测哪个clients 有数据就绪 */

            if ((sockfd = client[i]) < 0)
                continue;
            if (FD_ISSET(sockfd, &rset)) {

                if ((n = Read(sockfd, buf, sizeof(buf))) == 0) {    /* 当client关闭链接时,服务器端也关闭对应链接 */
                    Close(sockfd);
                    FD_CLR(sockfd, &allset);                        /* 解除select对此文件描述符的监控 */
                    client[i] = -1;
                } else if (n > 0) {
                    for (j = 0; j < n; j++)
                        buf[j] = toupper(buf[j]);
                    Write(sockfd, buf, n);
                    Write(STDOUT_FILENO, buf, n);
                }
                if (--nready == 0)
                    break;                                          /* 跳出for, 但还在while中 */
            }
        }
    }
    Close(listenfd);
    return 0;
}

/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>

#include "wrap.h"

#define MAXLINE 80
#define SERV_PORT 6666

int main(int argc, char *argv[])
{
    struct sockaddr_in servaddr;
    char buf[MAXLINE];
    int sockfd, n;

    if (argc != 2)
        printf("./client IP\n");

    sockfd = Socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    inet_pton(AF_INET, argv[1], &servaddr.sin_addr);
    servaddr.sin_port = htons(SERV_PORT);

    Connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
    printf("------------connect ok----------------\n");

    while (fgets(buf, MAXLINE, stdin) != NULL) {
        Write(sockfd, buf, strlen(buf));
        n = Read(sockfd, buf, MAXLINE);
        if (n == 0) {
            printf("the other side has been closed.\n");
            break;
        }
        else
            Write(STDOUT_FILENO, buf, n);
    }
    Close(sockfd);

    return 0;
}