{

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

struct sockaddr_in serv_addr;

serv_addr.sin_family = AF_INET;

serv_addr.sin_port = htons(8123);

//serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");

//将 inet_addr() 改用 inet_pton() 这个现代的方法，支持 IPV4 和 IPV6

if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr) == -1) {

printf("inet_pton error\n");

close(cli_sock);

return 0;

}

//将 inet_ntoa() 改用 inet_ntop() 这个现代方法，支持 IPV4 和 IPV6

//printf("bind in %s : %d\n", inet_ntoa(serv_addr.sin_addr), ntohs(serv_addr.sin_port));

//INET_ADDRSTRLEN 是标识 IPV4 地址展现字符串的大小常量,INET6_ADDRSTRLEN是 IPV6 的

char serv_ip[INET_ADDRSTRLEN];

if (inet_ntop(AF_INET, &serv_addr.sin_addr, serv_ip, sizeof(serv_ip)) == NULL) {

printf("inet_ntop error\n");

close(cli_sock);

return 0;

}

printf("bind in %s : %d\n", serv_ip, ntohs(serv_addr.sin_port));

int conn = connect(cli_sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr));

if (conn == -1) {

printf("connect error\n");

return 0;

}

char s[] = "hello world";

char buf[256];

write(cli_sock, s, strlen(s) + 1);

read(cli_sock, buf, sizeof(buf));

printf("read %s\n", buf);

close(cli_sock);

return 0;

}