#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
/*
 *  这个头文件用于网络字节序的转换
 *  htonl  ==>  host to network long
 *  htons  ==>  host to network short
 *  ntohl  ==>  network to host long
 *  ntohs  ==>  network to host shorts
*/

int main()
{
    int server = 0;
    struct sockaddr_in saddr = {0};  // 对应到头文件netinet/in.h中，这个结构体中的in是什么意思？
    int client = 0;
    struct sockaddr_in caddr = {0};
    socklen_t asize = 0;
    int len = 0;
    char buf[64] = {0};
    int r = 0;

    server = socket(PF_INET, SOCK_STREAM, 0);
    if (server == -1) {
        printf("server socket error\n");
        return -1;
    }

    saddr.sin_family = AF_INET;
    // 服务器每一个网卡对应一个IP地址，INADDR_ANY表示监听所有的网卡
    saddr.sin_addr.s_addr = htonl(INADDR_ANY);
    saddr.sin_port = htons(8899);

    if (bind(server, (struct sockaddr *)&saddr, sizeof(saddr)) == -1) {
        printf("server bind error\n");
        return -1;
    }

    if (listen(server, 1) == -1) {
        printf("server listen error\n");
        return -1;
    }

    printf("server start success\n");

    asize = sizeof(caddr);

    client = accept(server, (struct sockaddr *)&caddr, &asize);
    if (client == -1) {
        printf("client accept error\n");
        return -1;
    }

    printf("client: %d\n", client);

    len = 0;

    do {
        int i = 0;

        r = recv(client, buf, sizeof(buf), 0);

        if( r > 0 ) {
            len += r;
        }

        for(i = 0; i < r; i++) {
            printf("%c", buf[i]);
        }

    } while ( len < 64 );

    printf("\n");

    send(client, "Hello world!", 12, 0);

    sleep(1);  // 保证上述的字符串可以发送到网络上

    close(client);
    close(server);

    return 0;
}