//服务端
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#define MYPORT 3490 /*定义用户连接端口*/
#define BACKLOG 10 /*多少等待连接控制*/
int main(int argc, char *argv[])
{
    int sockfd, new_fd;/* listen on sock_fd, new connection on new_fd*/
    struct sockaddr_in my_addr; /* my address information */
    struct sockaddr_in their_addr; /* connector's address information */
    int sin_size;
    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
    {
        perror("socket");
        exit(1);
    }

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

    my_addr.sin_family = AF_INET; /* host byte order */
    my_addr.sin_port = htons(MYPORT); /* short, network byte order */
    my_addr.sin_addr.s_addr = INADDR_ANY; /* auto-fill with my IP */
    bzero(&(my_addr.sin_zero),0); /* zero the rest of the struct */

    if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr))== -1) 
    {
        perror("bind");
        exit(1);
    }
    if (listen(sockfd, BACKLOG) == -1) {
        perror("listen");
        exit(1);
    }

    while(1) { /* main accept() loop */
        sin_size = sizeof(struct sockaddr_in);
        printf("while\n");
        if ((new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size)) == -1) 
        {
            perror("accept");
            continue;
        }
        printf("server: got connection from %s\n", inet_ntoa(their_addr.sin_addr));

        while(1)
        {
            usleep(10000000);
            if (send(new_fd, "Hello, world!\n", 14, 0) == -1)
                perror("send");
        }
        close(new_fd);
        exit(0);

    }
    return 0;
}

//客户端
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netdb.h>
#define PORT 3490 /* 客户机连接远程主机的端口 */
#define MAXDATASIZE 100 /* 每次可以接收的最大字节 */
int main(int argc, char *argv[])
{
    int sockfd, numbytes;
    char buf[MAXDATASIZE];
    struct hostent *he;
    struct sockaddr_in their_addr; /* connector's address information */
    if (argc != 2) 
    {
        fprintf(stderr,"usage: client hostname\n");
        exit(1);
    }
    if ((he=gethostbyname(argv[1])) == NULL) 
    { /* get the host info */
        herror("gethostbyname");
        exit(1);
    }

    if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1) 
    {
        perror("socket");
        exit(1);
    }

    their_addr.sin_family = AF_INET; /* host byte order */
    their_addr.sin_port = htons(PORT); /* short, network byte order */
    their_addr.sin_addr = *((struct in_addr *)(he->h_addr));
    bzero(&(their_addr.sin_zero),0); /* zero the rest of the struct */
    if (connect(sockfd, (struct sockaddr *)&their_addr,sizeof(struct sockaddr)) == -1) 
    {
        perror("connect");
        exit(1);
    }
    while(1)
    {
        printf("receiving......\n");
        if ((numbytes=recv(sockfd, buf, MAXDATASIZE, 0)) == -1) 
        {
            perror("recv");
            exit(1);
        }
        buf[numbytes] = '\0';