주요 구조체
struct msg_start {
int type; /* Type of the Message - Request/Response */
int len; /* length including delimiter */
union {
struct {
str method; /* Method string */
str uri; /* Request URI */
str version; /* SIP version */
int method_value;
} request;
struct {
str version; /* SIP version */
str status; /* Reply status */
str reason; /* Reply reason phrase */
unsigned int /* statusclass,*/ statuscode;
} reply;
}u;
};