+ \r
+ The address of class A starts with 0.\r
+ If the address belong to class A, return IP4_ADDR_CLASSA.\r
+ The address of class B starts with 10. \r
+ If the address belong to class B, return IP4_ADDR_CLASSB.\r
+ The address of class C starts with 110. \r
+ If the address belong to class C, return IP4_ADDR_CLASSC.\r
+ The address of class D starts with 1110. \r
+ If the address belong to class D, return IP4_ADDR_CLASSD.\r
+ The address of class E starts with 1111.\r
+ If the address belong to class E, return IP4_ADDR_CLASSE.\r