eXosip事件总结：
EXosip使用UDP socket套接字实现底层sip协议的接收/发送。并且封装了sip消息的解释器。
EXosip使用定时轮循的方式调用Osip2的transaction处理函数，这部分是协议栈运转的核心。透过添加/读取transaction消息管道的方式，驱动transaction的状态机，使得来自远端的sip信令能汇报给调用程序，来自调用程序的反馈能通过sip信令回传给远端。
EXosip增加了对各个类型transaction的超时处理，确保所有资源都能循环使用，不会被耗用殆尽。
EXosip使用jevent消息管道来向上通知调用程序底层发生的事件，调用程序只要读取该消息管道，就能获得感兴趣的事件，进行相关的处理。
EXosip里比较重要的应用有j_calls、j_subscribes、j_notifies、j_reg、j_pub、osip_negotiation和authinfos。J_calls对应呼叫链表，记录所有当前活动的呼叫。J_reg对应注册链表，记录所有当前活动的注册信息。Osip_negotiation记录本地的能力集，用于能力交换。Authinfos记录需要的认证信息。
EXOSIP_REGISTRATION_NEW announce new registration. 宣布新的登记。
EXOSIP_REGISTRATION_SUCCESS user is successfully registred. 用户成功 registred
EXOSIP_REGISTRATION_FAILURE user is not registred. 用户不 registred
EXOSIP_REGISTRATION_REFRESHED registration has been refreshed. 注册已刷新
EXOSIP_REGISTRATION_TERMINATED UA is not registred any more. UA是没有任何更多的registred
EXOSIP_CALL_INVITE announce a new call 宣布一个新的呼叫
EXOSIP_CALL_REINVITE announce a new INVITE within call 调用一个内公布新的邀请
EXOSIP_CALL_NOANSWER announce no answer within the timeout 在超时内没有公布答案
EXOSIP_CALL_PROCEEDING announce processing by a remote app 公布一个远程应用程序处理
EXOSIP_CALL_RINGING announce ringback 公布电话铃响
EXOSIP_CALL_ANSWERED announce start of call 公布电话会议开始
EXOSIP_CALL_REDIRECTED announce a redirection 宣布重定向
EXOSIP_CALL_REQUESTFAILURE announce a request failure 宣布一个请求失败
EXOSIP_CALL_SERVERFAILURE announce a server failure 宣布一个服务器失败
EXOSIP_CALL_GLOBALFAILURE announce a global failure 宣布全球失败
EXOSIP_CALL_ACK ACK received for 200ok to INVITE 应答收到 200ok邀请
EXOSIP_CALL_CANCELLED announce that call has been cancelled 宣布这一呼吁已被取消
EXOSIP_CALL_TIMEOUT announce that call has failed 宣布，调用失败
EXOSIP_CALL_MESSAGE_NEW announce new incoming request. 宣布新传入的请求。
EXOSIP_CALL_MESSAGE_PROCEEDING announce a 1xx for request. 公布要求1xx 的。
EXOSIP_CALL_MESSAGE_ANSWERED announce a 200ok
EXOSIP_CALL_MESSAGE_REDIRECTED announce a failure.
EXOSIP_CALL_MESSAGE_REQUESTFAILURE announce a failure.
EXOSIP_CALL_MESSAGE_SERVERFAILURE announce a failure.
EXOSIP_CALL_MESSAGE_GLOBALFAILURE announce a failure.
EXOSIP_CALL_CLOSED a BYE was received for this call 一个BYE收到此呼吁
EXOSIP_CALL_RELEASED call context is cleared. 调用上下文被清除。
EXOSIP_MESSAGE_NEW announce new incoming request. 宣布新传入的请求。
EXOSIP_MESSAGE_PROCEEDING announce a 1xx for request.
EXOSIP_MESSAGE_ANSWERED announce a 200ok
EXOSIP_MESSAGE_REDIRECTED announce a failure.
EXOSIP_MESSAGE_REQUESTFAILURE announce a failure.
EXOSIP_MESSAGE_SERVERFAILURE announce a failure.
EXOSIP_MESSAGE_GLOBALFAILURE announce a failure.
EXOSIP_SUBSCRIPTION_UPDATE announce incoming SUBSCRIBE. 宣布进入订阅。
EXOSIP_SUBSCRIPTION_CLOSED announce end of subscription. 宣布认购结束。
EXOSIP_SUBSCRIPTION_NOANSWER announce no answer
EXOSIP_SUBSCRIPTION_PROCEEDING announce a 1xx
EXOSIP_SUBSCRIPTION_ANSWERED announce a 200ok
EXOSIP_SUBSCRIPTION_REDIRECTED announce a redirection
EXOSIP_SUBSCRIPTION_REQUESTFAILURE announce a request failure
EXOSIP_SUBSCRIPTION_SERVERFAILURE announce a server failure
EXOSIP_SUBSCRIPTION_GLOBALFAILURE announce a global failure
EXOSIP_SUBSCRIPTION_NOTIFY announce new NOTIFY request 宣布新的 NOTIFY请求
EXOSIP_SUBSCRIPTION_RELEASED call context is cleared.
EXOSIP_IN_SUBSCRIPTION_NEW announce new incoming SUBSCRIBE. 宣布新传入的订阅
EXOSIP_IN_SUBSCRIPTION_RELEASED announce end of subscription.
EXOSIP_NOTIFICATION_NOANSWER announce no answer
EXOSIP_NOTIFICATION_PROCEEDING announce a 1xx
EXOSIP_NOTIFICATION_ANSWERED announce a 200ok
EXOSIP_NOTIFICATION_REDIRECTED announce a redirection
EXOSIP_NOTIFICATION_REQUESTFAILURE announce a request failure
EXOSIP_NOTIFICATION_SERVERFAILURE announce a server failure
EXOSIP_NOTIFICATION_GLOBALFAILURE announce a global failure
EXOSIP_EVENT_COUNT MAX number of events