优化设备在线状态

src/main/java/com/genersoft/iot/vmp/gb28181/SipLayer.java

@@ -48,8 +48,15 @@ public class SipLayer{
 		Properties properties = new Properties();
 		properties.setProperty("javax.sip.STACK_NAME", "GB28181_SIP");
 		properties.setProperty("javax.sip.IP_ADDRESS", sipConfig.getMonitorIp());
+		/**
+		 * 完整配置参考 gov.nist.javax.sip.SipStackImpl，需要下载源码
+		 * gov/nist/javax/sip/SipStackImpl.class
+		 */
 		properties.setProperty("gov.nist.javax.sip.LOG_MESSAGE_CONTENT", "true");
 		properties.setProperty("gov.nist.javax.sip.DELIVER_UNSOLICITED_NOTIFY", "true"); // 接收所有notify请求，即使没有订阅
+		properties.setProperty("gov.nist.javax.sip.DELIVER_TERMINATED_EVENT_FOR_NULL_DIALOG", "true"); // 为_NULL _对话框传递_终止的_事件
+		properties.setProperty("gov.nist.javax.sip.RELEASE_REFERENCES_STRATEGY", "Normal"); // 会话清理策略
+		properties.setProperty("gov.nist.javax.sip.RELIABLE_CONNECTION_KEEP_ALIVE_TIMEOUT", "10");
 		/**
 		 * sip_server_log.log 和 sip_debug_log.log public static final int TRACE_NONE =
 		 * 0; public static final int TRACE_MESSAGES = 16; public static final int