Refactor sequence code into SequenceManager

Networks.go

@@ -0,0 +1,34 @@
+/*
+File Name:  Networks.go
+Copyright:  2021 Peernet s.r.o.
+Author:     Peter Kleissner
+*/
+
+package core
+
+// Networks is the collection of all connected networks
+type Networks struct {
+	// networks is a list of all connected networks
+	//networks4, networks6 []*Network
+
+	// Mutex for both network lists. Higher granularity currently not needed.
+	//sync.RWMutex
+	//networksMutex sync.RWMutex
+
+	// countListenX is the number of networks listened to, excluding link-local only listeners. This number might be different than len(networksN).
+	// This is useful to determine if there are any IPv4 or IPv6 listeners for potential external connections. This can be used to determine IPv4_LISTEN and IPv6_LISTEN.
+	//countListen4, countListen6 int64
+
+	Sequences *SequenceManager
+}
+
+//  ReplyTimeout is the round-trip timeout for message sequences.
+const ReplyTimeout = 20
+
+var networks *Networks
+
+func initMessageSequence() {
+	networks = &Networks{}
+
+	networks.Sequences = NewSequenceManager(ReplyTimeout)
+}