uip main函数分析1_IP地址的实现
uip_ipaddr_t ipaddr;
uip_ipaddr_t 定义：
/**
* Repressentation of an IP address.
*
*/
typedef u16_t uip_ip4addr_t[2];//uip_ip4addr_t为u16_t的数组类型，该数组类型有两个数据。
typedef u16_t uip_ip6addr_t[8];//同上
#if UIP_CONF_IPV6
typedef uip_ip6addr_t uip_ipaddr_t;//别名，用来存储IP地址，用两个16位的数据来存储32位的IP地址，具体实现如下。
#else /* UIP_CONF_IPV6 */
typedef uip_ip4addr_t uip_ipaddr_t;//别名
#endif /* UIP_CONF_IPV4 */
u16_t为16位的数据类型。 移植代码参考如下：typedef unsigned int u16_t;
main函数中另外的一个函数uip_ipaddr(ipaddr, 192,168,0,2);
uip_ipaddr函数（其实是一个macro）定义如下：
/** @} */
/* uIP convenience and converting functions. */
* These functions can be used for converting between different data formats used by uIP.
* Construct an IP address from four bytes
* This function constructs an IP address of the type that uIP handles internally from four bytes. The function is handy for specifying IP addresses to use with e.g. the uip_connect() function.
* Example:
\code
uip_ipaddr_t ipaddr;
struct uip_conn *c;
uip_ipaddr(&ipaddr, 192,168,1,2);
c = uip_connect(&ipaddr, HTONS(80));
\endcode
* \param addr A pointer to a uip_ipaddr_t variable that will be
* filled in with the IP address.
* \param addr0 The first octet of the IP address.
* \param addr1 The second octet of the IP address.
* \param addr2 The third octet of the IP address.
* \param addr3 The forth octet of the IP address.
*/
#define uip_ipaddr(addr, addr0,addr1,addr2,addr3) do { \
((u16_t *)(addr))[0] = HTONS(((addr0) << 8) | (addr1)); \
((u16_t *)(addr))[1] = HTONS(((addr2) << 8) | (addr3)); \
} while(0)
从上述英文介绍可知该宏用于存储IP地址，将IP地址存储在刚才所述的uip_ipaddr_t类型变量中，用于以后函数调用。
