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套接字编程select,poll,epoll

C/C++ admin 1248℃ 0评论

这是展示select,poll,epoll的例子,并添加注释,代码来自:

参考链接

客户端代码:

#include <unistd.h>
#include <sys/types.h>       /* basic system data types */
#include <sys/socket.h>      /* basic socket definitions */
#include <netinet/in.h>      /* sockaddr_in{} and other Internet defns */
#include <arpa/inet.h>       /* inet(3) functions */
#include <netdb.h> /*gethostbyname function */
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

#define MAXLINE 1024

void handle(int connfd);

int main(int argc, char **argv)
{
    char * servInetAddr = "127.0.0.1"; // 服务器端的IP地址
    int servPort = 6888; // 连接服务器端的端口
    char buf[MAXLINE];
    int connfd;
    struct sockaddr_in servaddr;

    if (argc == 2) {
        servInetAddr = argv[1];
    }
    if (argc == 3) {
        servInetAddr = argv[1];
        servPort = atoi(argv[2]);
    }
    if (argc > 3) {
        printf("usage: echoclient <IPaddress> <Port>\n");
        return -1;
    }

    connfd = socket(AF_INET, SOCK_STREAM, 0); // 创建套接字
    bzero(&servaddr, sizeof(servaddr)); // 清空服务器端地址
    servaddr.sin_family = AF_INET; //协议族
    servaddr.sin_port = htons(servPort); // 端口号
    inet_pton(AF_INET, servInetAddr, &servaddr.sin_addr);

    // 连接服务器端
    if (connect(connfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) {
        perror("connect error");
        return -1;
    }
    printf("welcome to echoclient\n");
    handle(connfd);     /* do it all */
    close(connfd);
    printf("exit\n");
    exit(0);
}

void handle(int sockfd)
{
    char sendline[MAXLINE], recvline[MAXLINE];
    int n;
    for (;;) {
        if (fgets(sendline, MAXLINE, stdin) == NULL) { // 从标准输入获取字符串
            break;//read eof
        }
        /*
        //也可以不用标准库的缓冲流,直接使用系统函数无缓存操作
        if (read(STDIN_FILENO, sendline, MAXLINE) == 0) {
            break;//read eof
        }
        */

        n = write(sockfd, sendline, strlen(sendline)); // 想套接字中的写入字符串
        n = read(sockfd, recvline, MAXLINE); // 从套接字中读取
        if (n == 0) {
            printf("echoclient: server terminated prematurely\n");
            break;
        }
        write(STDOUT_FILENO, recvline, n);
        //如果用标准库的缓存流输出有时会出现问题
        //fputs(recvline, stdout);
    }
}

阻塞模式服务器端

#include <unistd.h>
#include <sys/types.h>       /* basic system data types */
#include <sys/socket.h>      /* basic socket definitions */
#include <netinet/in.h>      /* sockaddr_in{} and other Internet defns */
#include <arpa/inet.h>       /* inet(3) functions */
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

#define MAXLINE 1024
//typedef struct sockaddr  SA;
void handle(int connfd);

int  main(int argc, char **argv)
{
    int listenfd, connfd; // 监听套接字,已连接套接字
    int serverPort = 6888; // 服务器端口
    int listenq = 1024;
    pid_t   childpid;
    char buf[MAXLINE];
    socklen_t socklen;

    // 服务器地址,客户端地址
    struct sockaddr_in cliaddr, servaddr; 
    socklen = sizeof(cliaddr);

    // 给服务器地址这个结构体的各个字段赋值
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(serverPort);

    // 创建监听套接字
    listenfd = socket(AF_INET, SOCK_STREAM, 0);
    if (listenfd < 0) { // 创建失败,小于0
        perror("socket error");
        return -1;
    }
    // 绑定监听套接字和服务器地址
    if (bind(listenfd, (struct sockaddr *) &servaddr, socklen) < 0) {
        perror("bind error");
        return -1;
    }
    // 大概是监听套接字最大连接数
    if (listen(listenfd, listenq) < 0) {
        perror("listen error");    
        return -1;
    }
    // 打印服务器端端口号
    printf("echo server startup,listen on port:%d\n", serverPort);
    for ( ; ; )  { // 死循环,用于客户端连接
        // 如果监听套接字接收到有客户端连接,则返回一个已连接套接字
        connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &socklen);
        if (connfd < 0) { perror("accept error"); continue; } // 打印对等方信息 sprintf(buf, "accept form %s:%d\n", inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port); printf(buf,""); childpid = fork(); if (childpid == 0) { /* child process */ close(listenfd); /* close listening socket */ handle(connfd); /* process the request */ exit (0); } else if (childpid > 0)  {
            close(connfd);          /* parent closes connected socket */
        } else {
            perror("fork error");
        }
    }
}


void handle(int connfd)
{
    size_t n;
    char buf[MAXLINE];

    for(;;) {
        // 从已连接套接字中读取消息
        n = read(connfd, buf, MAXLINE);
        if (n < 0) { // 如果读取的消息数目小于0,则说明出错了
            if(errno != EINTR) {
                perror("read error");
                break;
            }
        }
        // 读取到的消息等于0,说明套接字中没有消息,关闭已连接套接字
        if (n == 0) { 
            //connfd is closed by client
            close(connfd);
            printf("client exit\n");
            break;
        }
        //client exit
        // 特殊符号,退出
        if (strncmp("exit", buf, 4) == 0) {
            close(connfd);
            printf("client exit\n");
            break;
        }
        write(connfd, buf, n); //write maybe fail,here don't process failed error
    } 
}

select模式服务器

#include <unistd.h>
#include <sys/types.h>       /* basic system data types */
#include <sys/socket.h>      /* basic socket definitions */
#include <netinet/in.h>      /* sockaddr_in{} and other Internet defns */
#include <arpa/inet.h>       /* inet(3) functions */
#include <sys/select.h>       /* select function*/
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

#define MAXLINE 10240

void handle(int * clientSockFds, int maxFds, fd_set* pRset, fd_set* pAllset);

int  main(int argc, char **argv)
{
    int servPort = 6888; // 服务器端口
    int listenq = 1024;

    int  listenfd, connfd; // 监听套接字,已连接套接字
    struct sockaddr_in cliaddr, servaddr; // 定义服务器,客户端地址结构体
    socklen_t socklen = sizeof(struct sockaddr_in);
    int nready, nread;
    char buf[MAXLINE];
    int clientSockFds[FD_SETSIZE];
    fd_set allset, rset;
    int maxfd;

    listenfd = socket(AF_INET, SOCK_STREAM, 0); // 创建监听套接字
    if (listenfd < 0) {
        perror("socket error");
        return -1;
    }

    int opt = 1;
    if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) < 0) {
        perror("setsockopt error");    
    }  

	// 向服务器地址结构体中的各个字段赋值
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(servPort);

	// 绑定监听套接字和服务器地址
    if(bind(listenfd, (struct sockaddr*)&servaddr, socklen) == -1) {
        perror("bind error");
        exit(-1);
    }

    if (listen(listenfd, listenq) < 0) {
        perror("listen error");
        return -1;
    }

    int i = 0;
    for (i = 0; i< FD_SETSIZE; i++) 
        clientSockFds[i] = -1; 
    FD_ZERO(&allset); // 情况文件描述符集合
    FD_SET(listenfd, &allset); // 将监听套接字加入文件描述符集合
    maxfd = listenfd;    

    printf("echo server use select startup, listen on port %d\n", servPort);
    printf("max connection: %d\n", FD_SETSIZE);

    for ( ; ; )  {
        rset = allset; // 将套接字集合赋值给reset

		// nready是..
        nready = select(maxfd + 1, &rset, NULL, NULL, NULL);
        if (nready < 0) {
            perror("select error");
            continue;
        }
		// 如果监听套接字有返回
        if (FD_ISSET(listenfd, &rset)) {
			// 建立连接,返回已连接套接字
            connfd = accept(listenfd, (struct sockaddr*) &cliaddr, &socklen);
            if (connfd < 0) {
                perror("accept error");
                continue;
            }

			// 打印对等方信息
            sprintf(buf, "accept form %s:%d\n", inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port);
            printf(buf, "");

			// 将已连接套接字加入套接字存放的数组
            for (i = 0; i< FD_SETSIZE; i++) { if (clientSockFds[i] == -1) { clientSockFds[i] = connfd; break; } } // 如果套接字存放数组中没有空闲的地方,则关闭 if (i == FD_SETSIZE) { fprintf(stderr, "too many connection, more than %d\n", FD_SETSIZE); close(connfd); continue; } // 已连接套接字的文件描述符是否是最大的,如果是,则更新 if (connfd > maxfd)
                maxfd = connfd;

			// 将已连接套接字放入套接字集合
            FD_SET(connfd, &allset);
            if (--nready <= 0)
                continue;
        }

		// 存放套接字数组,最大套接字文件描述符,套接字集合
        handle(clientSockFds, maxfd, &rset, &allset); 
    }
}


void handle(int * clientSockFds, int maxFds, fd_set* pRset, fd_set* pAllset) {
    int nread;
    int i;
    char buf[MAXLINE];
    for (i = 0; i< maxFds; i++) {
        if (clientSockFds[i] != -1) {
            if (FD_ISSET(clientSockFds[i], pRset)) {
                nread = read(clientSockFds[i], buf, MAXLINE);//读取客户端socket流
                if (nread < 0) {
                    perror("read error");
                    close(clientSockFds[i]);
                    FD_CLR(clientSockFds[i], pAllset);
                    clientSockFds[i] = -1;
                    continue;
                }
                if (nread == 0) {
                    printf("client close the connection\n");
                    close(clientSockFds[i]);
                    FD_CLR(clientSockFds[i], pAllset);
                    clientSockFds[i] = -1;
                    continue;
                } 

                write(clientSockFds[i], buf, nread);//响应客户端  有可能失败,暂不处理
            }
        }
    }

}

Poll函数服务器

#include  <unistd.h>
#include  <sys/types.h>       /* basic system data types */
#include  <sys/socket.h>      /* basic socket definitions */
#include  <netinet/in.h>      /* sockaddr_in{} and other Internet defns */
#include  <arpa/inet.h>       /* inet(3) functions */

#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>


#include <poll.h> /* poll function */
#include <limits.h>

#define MAXLINE 10240

#ifndef OPEN_MAX
#define OPEN_MAX 40960
#endif

void handle(struct pollfd* clients, int maxClient, int readyClient);

int  main(int argc, char **argv)
{
    int servPort = 6888; // 端口信息
    int listenq = 1024; // listen等待的最大文件描述符
    int listenfd, connfd;
    struct pollfd clients[OPEN_MAX]; // poll打开的最大文件描述符
    int  maxi;
    socklen_t socklen = sizeof(struct sockaddr_in); // 地址长度
    struct sockaddr_in cliaddr, servaddr; // 服务器地址和客户端地址
    char buf[MAXLINE]; // bug长度
    int nready;

	// 初始化服务器地址
    bzero(&servaddr, socklen);
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(servPort);

	// 创建监听套接字
    listenfd = socket(AF_INET, SOCK_STREAM, 0);
    if (listenfd < 0) {
        perror("socket error");
    }

	// 保证地址可以重复利用
    int opt = 1;
    if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)) < 0) {
        perror("setsockopt error");
    }

	// 绑定监听套接字和服务器地址
    if(bind(listenfd, (struct sockaddr *) &servaddr, socklen) == -1) {
        perror("bind error");
        exit(-1);
    }
    if (listen(listenfd, listenq) < 0) {
        perror("listen error");    
    }

	// clients中的第一个套接字是监听套接字
    clients[0].fd = listenfd;
	// clients中的第一个套接字,我们关心的事件是POLLIN事件
    clients[0].events = POLLIN;
    int i;
	// 其他套接字置为-1
    for (i = 1; i< OPEN_MAX; i++) 
        clients[i].fd = -1; 
    maxi = listenfd + 1;

    printf("pollechoserver startup, listen on port:%d\n", servPort);
    printf("max connection is %d\n", OPEN_MAX);

    for ( ; ; )  {
		printf("For\n");
		// poll 函数,clients集合,最大文件描述符,不超时
        nready = poll(clients, maxi + 1, -1);
		printf("Poll End\n");
        //printf("nready is %d\n", nready);
        if (nready == -1) {
            perror("poll error");
        }
		// 如果clients中的第一个文件描述符有POLLIN事件
        if (clients[0].revents & POLLIN) {
			// 建立连接,返回已连接套接字
            connfd = accept(listenfd, (struct sockaddr *) &cliaddr, &socklen);
            sprintf(buf, "accept form %s:%d\n", inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port);
            printf(buf, "");

			// 将已连接套接字加入空闲位置,并对POLLIN事件感兴趣
            for (i = 0; i < OPEN_MAX; i++) {
                if (clients[i].fd == -1) {
                    clients[i].fd = connfd;
                    clients[i].events = POLLIN;
                    break;
                }
            }

			// 如果没有空闲位置了,则表明clients集合已经满了,关闭套接字
            if (i == OPEN_MAX) {
                fprintf(stderr, "too many connection, more than %d\n", OPEN_MAX);
                close(connfd);
                continue;
            }

            if (i > maxi)
                maxi = i;

            --nready;
        }

        handle(clients, maxi, nready);
    }
}

void handle(struct pollfd* clients, int maxClient, int nready) {
    int connfd;
    int i, nread;
    char buf[MAXLINE];
	printf("Print\n");

    if (nready == 0)
        return;

    for (i = 1; i< maxClient; i++) {
        connfd = clients[i].fd;
        if (connfd == -1) 
            continue;
        if (clients[i].revents & (POLLIN | POLLERR)) {
            nread = read(connfd, buf, MAXLINE);//读取客户端socket流
            if (nread < 0) {
                perror("read error");
                close(connfd);
                clients[i].fd = -1;
                continue;
            }
            if (nread == 0) {
                printf("client close the connection");
                close(connfd);
                clients[i].fd = -1;
                continue;
            }

            write(connfd, buf, nread);//响应客户端  
            if (--nready <= 0)//没有连接需要处理,退出循环
                break;
        }
    }
}

 

 

 

 

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