1.sockaddr结构体

struct sockaddr{
    unsigned short sa_family;    //地址类型，AF_XXX
    char sa_data[14];                //14字节的端口和地址
}

2.sockaddr_in结构体

struct sockaddr_in{
    short int sin_family;        //地址类型
    unsigned short int sin_port;    //端口号
    struct in_addr sin_addr;    //地址
    unsigned char sin_zero[8];    //为了保持与struct 的长度sockaddr一样的长度
}

3.in_addr结构体

struct addr_in{
    unsigned long s_addr;    //地址
}