Increase the minimal interval based on which coupler should send a

keep alive message. THis is not a sane value (1s) but is a temporary workaround
around real problem which is that in this implementation coupler's subscribe
implementation can not cope with flood of subscribed to it UDP diagrams.
Real solution to reach high avialability is to make coupler's UDP handling
use multithreading and signifficantly speed up UDP handling in Subscribe part.

coupler/opc-ua-server/keep_alive.h

@@ -18,7 +18,7 @@ static int HEART_BEAT_TIMEOUT_INTERVAL = DEFAULT_HEART_BEAT_TIMEOUT_INTERVAL;
 unsigned int HEART_BEAT_ID_LIST[] = {0, 0, 0, 0, 0, 0, 0, 0};
 
 // the interval for publishing messages$
-const int PUBLISHING_INTERVAL = 100;
+const int PUBLISHING_INTERVAL = 1000;
 
 // a hard coded writer group, data set and publisher ID$
 // (should be same for publisher / subscriber)$

coupler/opc-ua-server/keep_alive_publisher.h

@@ -53,6 +53,7 @@ static void addWriterGroup(UA_Server *server) {
     memset(&writerGroupConfig, 0, sizeof(UA_WriterGroupConfig));
     writerGroupConfig.name = UA_STRING("Demo WriterGroup");
     writerGroupConfig.publishingInterval = PUBLISHING_INTERVAL;
+    writerGroupConfig.keepAliveTime = PUBLISHING_INTERVAL;
     writerGroupConfig.enabled = UA_FALSE;
     writerGroupConfig.writerGroupId = WRITER_GROUP_ID;
     writerGroupConfig.encodingMimeType = UA_PUBSUB_ENCODING_UADP;