0
点赞
收藏
分享

微信扫一扫

套接字基础

Xin_So 2024-04-25 阅读 11
c++

套接字基础

套接字

一、socket

 int socket(int domain, int type, int protocol);
  • 参数一 domain:

  • 参数二 type:

  • 参数三 protocol:

    使用示例:

     int listenfd = socket(AF_INET, SOCK_STREAM, 0);
    

二、setsockopt

使用示例:

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

三、bind

#include <sys/socket.h>
 int bind(int sockfd, const struct sockaddr *addr,socklen_t addrlen);

sockaddr_in结构体

 struct sockaddr_in {
           sa_family_t     sin_family;     /* AF_INET */
           in_port_t       sin_port;       /* Port number */
           struct in_addr  sin_addr;       /* IPv4 address */
       };

这个结构体也是挺麻烦的,在使用之前我们需要进行初始化,因为我们一般的数据格式是无法在网络中传输了,需要转为特定格式才行,转格式就需要用到下面几个函数,头文件 #include <arpa/inet.h>

这个结构体在使用之前一般还需要清空

既然有从本地数据转为网络,自然也有从网络转本地的

使用示例:

struct sockaddr_in serverAddr;
bzero(&serverAddr, sizeof(serverAddr));
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(6666);
Inet_pton(AF_INET, "127.0.0.1", &serverAddr.sin_addr);
Bind(listenfd, (struct sockaddr*)&serverAddr, sizeof(serverAddr));

四、listen

使用示例:

listen(listenfd, 128);

五、select

#include <sys/select.h>
int select(int nfds, fd_set *_Nullable restrict readfds,
                  fd_set *_Nullable restrict writefds,
                  fd_set *_Nullable restrict exceptfds,
                  struct timeval *_Nullable restrict timeout);
//select 函数的返回值表示就绪的文件描述符数量

参数一 nfds:

参数二 ,三,四 readfdswritefdsexceptfds

参数三:

使用示例:

count = select(maxfd + 1, &rset, nullptr, nullptr, nullptr);

由于select函数设计的比较好,所有使用是来就略显的复杂,由于select函数只返回符合条件的文件描述符的总数,我们并不知道具体是哪个文件描述符符合,所有我们需要不断的遍历1024次(1024是select所支持的最大文件描述符数量),这样效率看起来就很低,在遍历的过程中我们还需要配合几个函数使用,当然,select也可以通过改变实现方式提高效率,如添加一个数组,等下可以看实现,现在先讲配合select使用的四个函数

void FD_CLR(int fd, fd_set *set); //从集合中删除某文件描述符,即断开连接时使用
int  FD_ISSET(int fd, fd_set *set);//查询某文件描述符是否在集合中
void FD_SET(int fd, fd_set *set);//将某文件描述符添加到集合中
void FD_ZERO(fd_set *set);//将集合清空,全部置0

关于为什么要每次都循环1024次,主要还是怕没检查到位而遗漏某请求,因为每有请求时都需要循环1024次,这样看起来效率就很低,关于为什么select还没有被淘汰,那就是它跨平台,耐打。关于使用数组优化,那就是在每添加一个请求时,将这个请求放入这个数组中,我们在某程度上就能减少循环次数,我们只需要循环 我们给定的数组就行,而不需要每次都遍历全部的连接文件描述符,借鉴于poll函数

/*select实现多路IO转接 */
#include <algorithm>
#include <iostream>
#include "wrap.h"

#define IPSERVER "127.0.0.1"
#define PORT 6666

int main() {
    /* Create a client[] array to make up for the problem of selecting looping 1024 times each time */
    int clientfd, client[FD_SETSIZE], listenfd, maxi, maxfd;
    char buf[BUFSIZ], str[INET_ADDRSTRLEN];
    struct sockaddr_in serverAddr, clientAddr;
    socklen_t clientAddrLen;
    fd_set rset, allset;

    listenfd = Socket(AF_INET, SOCK_STREAM, 0);
    int opt = 1;
    setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

    bzero(&serverAddr, sizeof(serverAddr));
    serverAddr.sin_family = AF_INET;
    Inet_pton(AF_INET, IPSERVER, &serverAddr.sin_addr);
    serverAddr.sin_port = htons(PORT);
    Bind(listenfd, (struct sockaddr*)&serverAddr, sizeof(serverAddr));

    Listen(listenfd, 128);

    FD_ZERO(&allset);
    FD_SET(listenfd, &allset);
    maxfd = listenfd;
    maxi = -1;

    for (int i = 0; i < FD_SETSIZE; i++) {
        client[i] = -1;
    }
    int count;
    clientAddrLen = sizeof(clientAddr);
    while (true) {
        rset = allset;
        count = select(maxfd + 1, &rset, nullptr, nullptr, nullptr);
        if (FD_ISSET(listenfd, &rset)) {
            int i;
            clientfd = Accept(listenfd, (struct sockaddr*)&clientAddr, &clientAddrLen);
            for (i = 0; i < FD_SETSIZE; i++) {
                if (client[i] < 0) {
                    client[i] = clientfd;
                    break;
                }
            }
            if (maxi == FD_SETSIZE) {
                perr_exit("文件描述符已满");
                continue;
            }
            maxi = std::max(i, maxi);
            maxfd = std::max(clientfd, maxfd);

            FD_SET(clientfd, &allset);
            if (count == 1)
                continue;
        }
        for (int i = 0; i <= maxi; i++) {
            if (FD_ISSET(client[i], &rset)) {
                int n = Read(client[i], buf, BUFSIZ);
                if (n == 0) {
                    Close(client[i]);
                    FD_CLR(client[i], &allset);
                    client[i] = -1;
                }
                Write(STDOUT_FILENO, buf, n);
                for (int j = 0; j < n; ++j) {
                    buf[j] = toupper(buf[j]);
                }
                Write(client[i], buf, n);
            }
        }
    }
    return 0;
}

六、poll

#include <poll.h>
int poll(struct pollfd *fds, nfds_t nfds, int timeout);
//返回值大于0,表示符合条件的总文件描述符数,等于0表示在指定的超时期间内没有任何事件发生,-1表示发生错误,错误原因存储在全局变量 errno 中。

参数一 fds:

参数二 nfds

参数三 timeout:

示例:

struct pollfd client[FD_SETSIZE];
int nready = poll(client, maxi + 1, -1);
#include <poll.h>
#include <algorithm>
#include <iostream>
#include "wrap.h"

#define IPADDR "127.0.0.1"
#define PORT 6666

int main() {
    int clientfd, listenfd, maxi, n;
    char buf[BUFSIZ], str[INET_ADDRSTRLEN];
    struct sockaddr_in serverAddr, clientAddr;
    socklen_t clientAddrLen;
    struct pollfd client[FD_SETSIZE];

    listenfd = Socket(AF_INET, SOCK_STREAM, 0);
    int opt = 1;
    setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

    bzero(&serverAddr, sizeof(serverAddr));
    serverAddr.sin_family = AF_INET;
    Inet_pton(AF_INET, IPADDR, &serverAddr.sin_addr);
    serverAddr.sin_port = htons(PORT);
    Bind(listenfd, (struct sockaddr*)&serverAddr, sizeof(serverAddr));

    Listen(listenfd, 128);
    client[0].fd = listenfd;
    client[0].events = POLLIN;
    for (int i = 1; i < FD_SETSIZE; i++) {
        client[i].fd = -1;
    }

    while (1) {
        int nready = poll(client, maxi + 1, -1);
        if (nready < 0) {
            perror("poll error");
            exit(1);
        }

        if (client[0].revents & POLLIN) {  // New connection
            int i;
            clientAddrLen = sizeof(clientAddr);
            clientfd = accept(listenfd, (struct sockaddr*)&clientAddr, &clientAddrLen);
            for (i = 1; i < FD_SETSIZE; i++) {
                if (client[i].fd < 0) {
                    client[i].fd = clientfd;
                    break;
                }
            }
            if (i == FD_SETSIZE) {
                printf("Too many clients\n");
                close(clientfd);
                continue;
            }

            client[i].events = POLLIN;
            if (i > maxi)
                maxi = i;
            if (--nready <= 0)
                continue;
        }

        for (int i = 1; i <= maxi; i++) {  // Check all clients for data
            if (client[i].fd < 0)
                continue;
            if (client[i].revents & (POLLIN | POLLERR)) {
                n = read(client[i].fd, buf, BUFSIZ);
                if (n < 0) {
                    perror("read error");
                    close(client[i].fd);
                    client[i].fd = -1;
                } else if (n == 0) {
                    printf("Client closed connection\n");
                    close(client[i].fd);
                    client[i].fd = -1;
                } else {
                    write(client[i].fd, buf, n);   // Echo back
                    write(STDOUT_FILENO, buf, n);  // Echo back
                }
            }
        }
    }
    return 0;
}

七、epoll

  • epoll_create函数:
  • epoll_ctl函数

参数一 epfd:

参数二 op:

参数三 fd:

参数四 event:

  • epoll_wait函数

参数一 apfd:

参数二 events

参数三 maxevents

参数四 timeout

//示例:
struct epoll_event temp, client[FD_SETSIZE];
ret = epoll_wait(epfd, client, 128, -1);
#include <sys/epoll.h>
#include <sys/socket.h>
#include <unistd.h>
#include <iostream>
#include "wrap.h"

int main() {
    int listenfd, clientfd;
    socklen_t clientAddrLen;
    struct sockaddr_in serverAddr, clientAddr;
    char buf[BUFSIZ];
    listenfd = socket(AF_INET, SOCK_STREAM, 0);

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

    bzero(&serverAddr, sizeof(serverAddr));
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(6666);
    Inet_pton(AF_INET, "127.0.0.1", &serverAddr.sin_addr);
    Bind(listenfd, (struct sockaddr*)&serverAddr, sizeof(serverAddr));
    Listen(listenfd, 128);
    /* 创建红黑树,得到句柄 */
    int epfd = epoll_create(128);
    /* temp用于设置单个fd的属性 */
    struct epoll_event temp, client[FD_SETSIZE];
    temp.events = EPOLLIN;
    temp.data.fd = listenfd;

    epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &temp);
    int ret, n;
    clientAddrLen = sizeof(clientAddr);
    while (true) {
        ret = epoll_wait(epfd, client, 128, -1);
        for (int i = 0; i < ret; ++i) {
            if (listenfd == client[i].data.fd) {
                clientfd = Accept(listenfd, (struct sockaddr*)&clientAddr, &clientAddrLen);
                client[i].data.fd = clientfd;
                temp.events = EPOLLIN;
                temp.data.fd = clientfd;
                epoll_ctl(epfd, EPOLL_CTL_ADD, clientfd, &temp);
            } else {
                n = Read(client[i].data.fd, buf, sizeof(buf));
                if (n == 0) {
                    Close(client[i].data.fd);
                    epoll_ctl(epfd, EPOLL_CTL_DEL, client[i].data.fd, &temp);
                } else {
                    Write(STDOUT_FILENO, buf, n);
                }
            }
        }
    }

    return 0;
}

一、水平模式(Level-Triggered,LT)

二、边沿模式(Edge-Triggered,ET)

从**水平模式转为边沿模式,**只需要或上EPOLLET

#include <sys/epoll.h>

int epfd = epoll_create1(0);
if (epfd == -1) {
    perror("epoll_create1");
    exit(EXIT_FAILURE);
}

struct epoll_event event;
int fd = ...; // 这里 fd 是你需要监控的文件描述符

event.events = EPOLLIN | EPOLLET; // 设置为边缘触发模式
event.data.fd = fd;

if (epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &event) == -1) {
    perror("epoll_ctl");
    exit(EXIT_FAILURE);
}

边沿模式需要配合 无阻塞和忙轮询,我们的epoll反应堆就是基于边沿模式,无阻塞,忙轮询,回调实现的

// epoll ET
#include <fcntl.h>
#include <sys/epoll.h>
#include <sys/socket.h>
#include <unistd.h>
#include <iostream>
#include "wrap.h"

int main() {
    int listenfd, clientfd;
    socklen_t clientAddrLen;
    struct sockaddr_in serverAddr, clientAddr;
    char buf[BUFSIZ];
    listenfd = socket(AF_INET, SOCK_STREAM, 0);

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

    bzero(&serverAddr, sizeof(serverAddr));
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(6666);
    Inet_pton(AF_INET, "127.0.0.1", &serverAddr.sin_addr);
    Bind(listenfd, (struct sockaddr*)&serverAddr, sizeof(serverAddr));
    Listen(listenfd, 128);

    int epfd = epoll_create(128);
    struct epoll_event temp, client[FD_SETSIZE];
    temp.events = EPOLLIN | EPOLLET;  // 设置ET模式_ET
    // temp.events = EPOLLIN;
    temp.data.fd = listenfd;

    epoll_ctl(epfd, EPOLL_CTL_ADD, listenfd, &temp);
    int ret, n;
    clientAddrLen = sizeof(clientAddr);
    while (true) {
        ret = epoll_wait(epfd, client, 128, -1);
        for (int i = 0; i < ret; ++i) {
            if (listenfd == client[i].data.fd) {
                clientfd = Accept(listenfd, (struct sockaddr*)&clientAddr, &clientAddrLen);
                //     设置非阻塞
                int flags = fcntl(clientfd, F_GETFL, -1);
                flags |= O_NONBLOCK;
                fcntl(clientfd, F_SETFL, flags);
                client[i].data.fd = clientfd;
                temp.events = EPOLLIN;
                temp.data.fd = clientfd;
                epoll_ctl(epfd, EPOLL_CTL_ADD, clientfd, &temp);
            } else {
                while (true) {
                    n = read(client[i].data.fd, buf, sizeof(buf));
                    if (n > 0) {
                        write(STDOUT_FILENO, buf, n);
                    } else if (n == -1 && errno == EAGAIN) {
                        break;  // 没有更多数据
                    } else if (n == 0) {
                        // 客户端关闭了连接
                        close(client[i].data.fd);
                        epoll_ctl(epfd, EPOLL_CTL_DEL, client[i].data.fd, NULL);
                        break;
                    } else {
                        // 处理其他错误
                        perror("Read error");
                        close(client[i].data.fd);
                        epoll_ctl(epfd, EPOLL_CTL_DEL, client[i].data.fd, NULL);
                        break;
                    }
                }
            }
        }
    }

    return 0;
}
举报

相关推荐

0 条评论