diff --git a/cmd/coap/main.go b/cmd/coap/main.go
index 160b7881..d4a3e789 100644
--- a/cmd/coap/main.go
+++ b/cmd/coap/main.go
@@ -33,9 +33,8 @@ func main() {
 	nc := connectToNats(cfg, logger)
 	defer nc.Close()
 
-	nats.StoreConnection(nc)
-
-	ca := adapter.NewCoAPAdapter(logger)
+	repo := nats.NewMessageRepository(nc)
+	ca := adapter.NewCoAPAdapter(logger, repo)
 
 	nc.Subscribe("msg.http", ca.MsgHandler)
 	nc.Subscribe("msg.mqtt", ca.MsgHandler)
diff --git a/coap/adapter.go b/coap/adapter.go
index e0a911c3..7f0b8a49 100644
--- a/coap/adapter.go
+++ b/coap/adapter.go
@@ -20,12 +20,14 @@ type Observer struct {
 type CoAPAdapter struct {
 	obsMap map[string][]Observer
 	logger *zap.Logger
+	repo   writer.MessageRepository
 }
 
 // NewCoAPAdapter creates new CoAP adapter struct
-func NewCoAPAdapter(logger *zap.Logger) *CoAPAdapter {
+func NewCoAPAdapter(logger *zap.Logger, repo writer.MessageRepository) *CoAPAdapter {
 	ca := &CoAPAdapter{
 		logger: logger,
+		repo:   repo,
 	}
 
 	ca.obsMap = make(map[string][]Observer)
diff --git a/coap/messages.go b/coap/messages.go
index 91abfbc7..add648ee 100644
--- a/coap/messages.go
+++ b/coap/messages.go
@@ -7,14 +7,13 @@ import (
 
 	mux "github.com/dereulenspiegel/coap-mux"
 	coap "github.com/dustin/go-coap"
-	"github.com/mainflux/mainflux/coap/nats"
 	"github.com/mainflux/mainflux/writer"
 )
 
 // sendMessage sends the message to NATS
 func (ca *CoAPAdapter) sendMessage(l *net.UDPConn, a *net.UDPAddr, m *coap.Message) *coap.Message {
 	log.Printf("Got message in sendMessage: path=%q: %#v from %v", m.Path(), m, a)
-	var res *coap.Message = nil
+	var res *coap.Message
 	if m.IsConfirmable() {
 		res = &coap.Message{
 			Type:      coap.Acknowledgement,
@@ -43,15 +42,15 @@ func (ca *CoAPAdapter) sendMessage(l *net.UDPConn, a *net.UDPAddr, m *coap.Messa
 	n.Protocol = "coap"
 	n.Payload = m.Payload
 
-	if err := nats.Send(n); err != nil {
+	if err := ca.repo.Save(n); err != nil {
 		if m.IsConfirmable() {
-			res.Payload = []byte("{\"error\": \"cannot publish\"}")
+			res.Code = coap.InternalServerError
 		}
 		return res
 	}
 
 	if m.IsConfirmable() {
-		res.Payload = []byte("{\"res\": \"sent\"}")
+		res.Code = coap.Changed
 	}
 	return res
 }
@@ -86,7 +85,7 @@ func (ca *CoAPAdapter) deregisterObserver(o Observer, cid string) {
 // observeMessage adds client to the observers map
 func (ca *CoAPAdapter) observeMessage(l *net.UDPConn, a *net.UDPAddr, m *coap.Message) *coap.Message {
 	log.Printf("Got message in observeMessage: path=%q: %#v from %v", m.Path(), m, a)
-	var res *coap.Message = nil
+	var res *coap.Message
 
 	if m.IsConfirmable() {
 		res = &coap.Message{
@@ -109,30 +108,33 @@ func (ca *CoAPAdapter) observeMessage(l *net.UDPConn, a *net.UDPAddr, m *coap.Me
 		message: m,
 	}
 
-	if m.Option(coap.Observe) != nil {
-		if value, ok := m.Option(coap.Observe).(uint32); ok {
-			if value == 0 {
-				ca.registerObserver(o, cid)
-			} else {
-				ca.deregisterObserver(o, cid)
-			}
+	if m.Option(coap.Observe) == nil {
+		if m.IsConfirmable() {
+			res.Code = coap.BadRequest
+		}
+		return res
+	}
+
+	if value, ok := m.Option(coap.Observe).(uint32); ok {
+		if value == 0 {
+			ca.registerObserver(o, cid)
 		} else {
-			// Interop - old deregister was when there was no Observe option provided
 			ca.deregisterObserver(o, cid)
 		}
+	} else {
+		// Interop - old deregister was when there was no Observe option provided
+		ca.deregisterObserver(o, cid)
 	}
 
 	if m.IsConfirmable() {
-		res.Payload = []byte("{\"res\": \"observing\"}")
+		res.Code = coap.Valid
 	}
 	return res
 }
 
 // obsTransmit transmits the message to observing clients
 func (ca *CoAPAdapter) obsTransmit(n writer.RawMessage) {
-
 	for _, v := range ca.obsMap[n.Channel] {
-
 		msg := *(v.message)
 		msg.Payload = n.Payload
 
diff --git a/coap/nats/messages.go b/coap/nats/messages.go
index 42dc62c3..eedb7353 100644
--- a/coap/nats/messages.go
+++ b/coap/nats/messages.go
@@ -10,18 +10,25 @@ import (
 
 const topic string = "msg.coap"
 
-// Stored NATS connection
-var snc *broker.Conn
+var _ writer.MessageRepository = (*natsRepository)(nil)
 
-func StoreConnection(nc *broker.Conn) {
-	snc = nc
+type natsRepository struct {
+	nc *broker.Conn
 }
 
-func Send(msg writer.RawMessage) error {
+// NewMessageRepository instantiates NATS message repository. Note that the
+// repository will not truly persist messages, but instead they will be
+// published to the topic and made available for persisting by all interested
+// parties, i.e. the message-writer service.
+func NewMessageRepository(nc *broker.Conn) writer.MessageRepository {
+	return &natsRepository{nc}
+}
+
+func (repo *natsRepository) Save(msg writer.RawMessage) error {
 	b, err := json.Marshal(msg)
 	if err != nil {
 		return err
 	}
 
-	return snc.Publish(topic, b)
+	return repo.nc.Publish(topic, b)
 }