socket編程 -- epoll模型服務端/客戶端通信的實現

https://blog.csdn.net/y396397735/article/details/50680359

本例實現如下功能： 

支持多客戶端與一個服務端進行通信，客戶端給服務端發送字符串數據，服務端將字符串中小寫轉爲大寫後發送回客戶端，客戶端打印輸出經轉換後的字符串。 
例如：發送abcde，打印輸出ABCDE 
服務端源碼如下：

/*server.c*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/epoll.h>
#include <errno.h>

#define BUFSIZE 666
#define SERV_PORT 8000
#define OPEN_MAX 1024

int main()
{
    int i, j, maxi, listenfd, connfd, sockfd;
    int nready, efd, res;
    ssize_t n;
    char buf[BUFSIZE], str[INET_ADDRSTRLEN];
    socklen_t clilen;
    int client[OPEN_MAX];
    struct sockaddr_in cliaddr, servaddr;

    struct epoll_event tep, ep[OPEN_MAX];//監聽事件
    /*分配一個網絡通信套接字，監聽文件描述符listenfd*/
    listenfd = socket(AF_INET, SOCK_STREAM, 0);
    /*初始化 IP類型 端口*/
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(SERV_PORT);
    /*將listenfd綁定服務端地址*/
    bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr));

    /*監聽請求*/
    listen(listenfd, 20);
    /*將客戶端標識初始化爲-1*/
    for(i = 0; i < OPEN_MAX; i++){
        client[i] = -1;
    }
    maxi = -1;
    /*告訴內核要監聽的文件描述符個數 OPEN_MAX = 1024*/
    efd = epoll_create(OPEN_MAX);

    if(efd == -1){
        perror("epoll_create");
    }

    tep.events = EPOLLIN;/*監聽文件描述符的可讀事件*/
    tep.data.fd = listenfd;/*設置爲監聽的文件描述符*/
    /*控制epoll監控的文件描述符上的事件*/
    res = epoll_ctl(efd, EPOLL_CTL_ADD/*註冊新的fd到efd*/, listenfd, &tep);

    if(res == -1)
        perror("epoll_ctl");

    for(;;){
        /*等待所監控文件描述符上有事件的產生，阻塞監聽*/
        nready = epoll_wait(efd, ep, OPEN_MAX, -1);
        if(nready == -1)
            perror("epoll_wait");
        for(i = 0; i < nready; i++){
            if(!(ep[i].events & EPOLLIN))/*若不是EPOLLIN事件，不做往下的處理*/
                continue;
            if(ep[i].data.fd == listenfd){ /*若是EPOLLIN，執行連接，接受請求*/
                clilen = sizeof(cliaddr);
                /*接受請求，分配新文件描述符connfd進行通信*/
                connfd = accept(listenfd, (struct sockaddr*)&cliaddr, &clilen);
                printf("received from %s at PORT %d\n", (char*)inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)), ntohs(cliaddr.sin_port));

                /*若將此新客戶端添加至客戶端集中*/
                for(j = 0; j < OPEN_MAX; j++)
                    if(client[j] < 0){
                        client[j] = connfd;
                        break;
                    }
                if(j == OPEN_MAX)
                    perror("客戶端超過限制");

                if(j > maxi)
                    maxi = j;//保證maxi爲最大文件描述符

                tep.events = EPOLLIN;
                tep.data.fd = connfd;
                res = epoll_ctl(efd, EPOLL_CTL_ADD/*註冊新的connfd到efd*/, connfd, &tep);
                if(res == -1)
                    perror("epoll_ctl");
            }else{/*處理efd中監聽的客戶端請求*/
                sockfd = ep[i].data.fd;
                n = read(sockfd, buf, BUFSIZE);
                if(n == 0){ /*讀取若爲空*/
                    for(j = 0; j <= maxi; j++){
                        if(client[j] == sockfd){
                            client[j] = -1;
                            break;
                        }
                    }
                    /*清除對sockfd文件描述符事件的監聽*/
                    res = epoll_ctl(efd, EPOLL_CTL_DEL, sockfd, NULL);
                    if(res == -1)
                        perror("epoll_ctl");
                    close(sockfd);
                    printf("client[%d] closed connection\n", j);
                }else{/*非空則處理客戶端信息*/
                    for(j = 0; j<n; j++)
                        buf[j] = toupper(buf[j]);
                    /*寫入與客戶端通信的文件描述符sockfd*/
                    write(sockfd, buf, n);
                }
            }
        }
    }
    /*關閉監聽*/
    close(listenfd);
    close(efd);
    return 0;
}

客戶端源碼如下：

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

#define BUFSIZE 666
#define SERV_PORT 8000
#define OPEN_MAX 1024

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

    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
    servaddr.sin_port = htons(SERV_PORT);

    /*連接服務端*/
    connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr));

    while(fgets(buf, BUFSIZE, stdin) != NULL){
        /*通過sockfd給服務端發送數據*/
        write(sockfd, buf, strlen(buf));
        n = read(sockfd, buf, BUFSIZE);
        if(n == 0)
            printf("the other side has been closed.\n");
        else/*打印輸出服務端傳過來的數據*/
            write(STDOUT_FILENO, buf, n);
    }

    close(sockfd);
    return 0;
}

---

編譯及執行

在終端1先執行：

yu@ubuntu:~/Linux/217/epoll$ ls
client.c  server.c
yu@ubuntu:~/Linux/217/epoll$ gcc -o client client.c
yu@ubuntu:~/Linux/217/epoll$ gcc -o server server.c
yu@ubuntu:~/Linux/217/epoll$ ./server

• 1
• 2
• 3
• 4
• 5

另開一終端2：

yu@ubuntu:~/Linux/217/epoll$ ./client
hey how are you
HEY HOW ARE YOU
bye
BYE

• 
  

再另開一終端3：

yu@ubuntu:~/Linux/217/epoll$ ./client
i am here 007
I AM HERE 007
hehe
HEHE

• 
  

最後開一終端4：

yu@ubuntu:~/Linux/217/epoll$ ./client
i am 008
I AM 008
zai jian
ZAI JIAN

• 
  

關閉3個客戶端(CTR+C)後服務端窗口：

yu@ubuntu:~/Linux/217/epoll$ ./server
received from 127.0.0.1 at PORT 58385
received from 127.0.0.1 at PORT 58386
received from 127.0.0.1 at PORT 58387
client[2] closed connection
client[1] closed connection
client[0] closed connection

•