网络编程TCP socket简单demo

#include    <sys/types.h>    /* basic system data types */
#include    <sys/socket.h>    /* basic socket definitions */
#include    <sys/time.h>    /* timeval{} for select() */
#include    <time.h>        /* timespec{} for pselect() */
#include    <netinet/in.h>    /* sockaddr_in{} and other Internet defns */
#include    <arpa/inet.h>    /* inet(3) functions */
#include    <errno.h>
#include    <fcntl.h>        /* for nonblocking */
#include    <netdb.h>
#include    <signal.h>
#include    <stdio.h>
#include    <stdlib.h>
#include    <string.h>
#include    <sys/stat.h>    /* for S_xxx file mode constants */
#include    <sys/uio.h>        /* for iovec{} and readv/writev */
#include    <unistd.h>
#include    <sys/wait.h>
#include    <sys/un.h>        /* for Unix domain sockets */
#include    <sys/select.h>    /* for convenience */
#include    <sys/sysctl.h>
#include    <poll.h>        /* for convenience */
#include    <strings.h>        /* for convenience */
#include    <sys/ioctl.h>
#include    <pthread.h>

size_t readn(int fd, void *buffer, size_t size) {
    char *buffer_pointer = buffer;
    int length = size;

    while (length > 0) {
        int result = read(fd, buffer_pointer, length);

        if (result < 0) {
            if (errno == EINTR)
                continue;     /* 考虑非阻塞的情况，这里需要再次调用read */
            else
                return (-1);
        } else if (result == 0)
            break;                /* EOF(End of File)表示套接字关闭 */

        length -= result;
        buffer_pointer += result;
    }
    return (size - length);        /* 返回的是实际读取的字节数*/
}

void read_data(int sockfd) {
    ssize_t n;
    char buf[1024];

    int time = 0;
    for (;;) {
        fprintf(stdout, "block in read\n");
        if ((n = readn(sockfd, buf, 1024)) == 0)
            return;

        time++;
        fprintf(stdout, "1K read for %d \n", time);
        // 接收设置延迟时间，观察client发送数据和server接收数据，client将数据写入到缓冲区之后就会立即返回成功
        sleep(5);
    }
}




int main(int argc, char **argv) {
    int listenfd, connfd;
    socklen_t clilen;
    // 声明地址信息结构体
    struct sockaddr_in cliaddr, servaddr;
    // 创建套接字
    listenfd = socket(AF_INET, SOCK_STREAM, 0);
    // 将指定内存区域的前 n 个字节全部设置为零，用于初始化内存区域
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    // INADDR_ANY IPv4通配地址 IN6ADDR_ANY IPv6通配地址
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    // 设置端口号，设置为0时由操作系统选择一个空闲的端口
    // htons函数：将一个无符号短整型（通常是16位）的主机数值转换为网络字节顺序
    servaddr.sin_port = htons(12345);

    // bind到本地地址，端口为12345 
    // bind函数套接字和地址关联
    bind(listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr));
    // 初始化创建的套接字，可以认为是一个"主动"套接字，其目的是之后主动发起请求
    // 通过 listen 函数，可以将原来的"主动"套接字转换为"被动"套接字
    listen(listenfd, 1024);

    /* 循环处理用户请求 */
    for (;;) {
        clilen = sizeof(cliaddr);
        // 客户端发起连接请求，accept函数接受请求建立连接
        // 第一个参数listenfd是用于监听的套接字，返回的是新建立连接的套接字
        connfd = accept(listenfd, (struct sockaddr *) &cliaddr, &clilen);
        read_data(connfd);   /* 读取数据 */
        close(connfd);          /* 关闭连接套接字，注意不是监听套接字*/
    }
}

#include    <sys/types.h>    /* basic system data types */
#include    <sys/socket.h>    /* basic socket definitions */
#include    <sys/time.h>    /* timeval{} for select() */
#include    <time.h>        /* timespec{} for pselect() */
#include    <netinet/in.h>    /* sockaddr_in{} and other Internet defns */
#include    <arpa/inet.h>    /* inet(3) functions */
#include    <errno.h>
#include    <fcntl.h>        /* for nonblocking */
#include    <netdb.h>
#include    <signal.h>
#include    <stdio.h>
#include    <stdlib.h>
#include    <string.h>
#include    <sys/stat.h>    /* for S_xxx file mode constants */
#include    <sys/uio.h>        /* for iovec{} and readv/writev */
#include    <unistd.h>
#include    <sys/wait.h>
#include    <sys/un.h>        /* for Unix domain sockets */
#include    <sys/select.h>    /* for convenience */
#include    <sys/sysctl.h>
#include    <poll.h>        /* for convenience */
#include    <strings.h>        /* for convenience */
#include    <sys/ioctl.h>
#include    <pthread.h>
#include    <stdarg.h>        /* ANSI C header file */
#include    <syslog.h>        /* for syslog() */

# define MESSAGE_SIZE 102400

void error(int status, int err, char *fmt, ...) {
    va_list ap;

    va_start(ap, fmt);
    vfprintf(stderr, fmt, ap);
    va_end(ap);
    if (err)
        fprintf(stderr, ": %s (%d)\n", strerror(err), err);
    if (status)
        exit(status);
}

void send_data(int sockfd) {
    char *query;
    query = malloc(MESSAGE_SIZE + 1);
    for (int i = 0; i < MESSAGE_SIZE; i++) {
        query[i] = 'a';
    }
    query[MESSAGE_SIZE] = '\0';

    const char *cp;
    cp = query;
    size_t remaining = strlen(query);
    while (remaining) {
        int n_written = send(sockfd, cp, remaining, 0);
        fprintf(stdout, "send into buffer %d \n", n_written);
        if (n_written <= 0) {
            error(1, errno, "send failed");
            return;
        }
        remaining -= n_written;
        cp += n_written;
    }

    return;
}

int main(int argc, char **argv) {
    int sockfd;
    struct sockaddr_in servaddr;

    if (argc != 2)
        error(1, 0, "usage: tcpclient <IPaddress>");

    sockfd = socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(12345);
    inet_pton(AF_INET, argv[1], &servaddr.sin_addr);
    int connect_rt = connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr));
    if (connect_rt < 0) {
        error(1, errno, "connect failed ");
    }
    send_data(sockfd);
    exit(0);
}