diff --git a/messaging/relayer/cmd/observer/main.go b/messaging/relayer/cmd/observer/main.go
index 3266834a..a5b760e9 100644
--- a/messaging/relayer/cmd/observer/main.go
+++ b/messaging/relayer/cmd/observer/main.go
@@ -16,16 +16,14 @@ package main
  */
 
 import (
-	"encoding/hex"
 	"encoding/json"
 
 	"github.com/consensys/gpact/messaging/relayer/internal/adminserver"
 	"github.com/consensys/gpact/messaging/relayer/internal/config"
 	"github.com/consensys/gpact/messaging/relayer/internal/contracts/functioncall"
 	"github.com/consensys/gpact/messaging/relayer/internal/logging"
-	v1 "github.com/consensys/gpact/messaging/relayer/internal/messages/v1"
 	"github.com/consensys/gpact/messaging/relayer/internal/mqserver"
-	"github.com/ethereum/go-ethereum/accounts/abi/bind"
+	"github.com/consensys/gpact/messaging/relayer/internal/msgobserver/eth"
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/ethclient"
 	_ "github.com/joho/godotenv/autoload"
@@ -75,7 +73,6 @@ func main() {
 		activeChains[request.BcID] = end
 
 		go func() {
-			// TODO: User msgobserver.
 			chain, err := ethclient.Dial(request.Chain)
 			if err != nil {
 				logging.Error(err.Error())
@@ -88,48 +85,13 @@ func main() {
 				logging.Error(err.Error())
 				return
 			}
-			sink := make(chan *functioncall.SfcCrossCall)
-			event, err := sfc.WatchCrossCall(&bind.WatchOpts{Start: nil, Context: nil}, sink)
+
+			observer, err := eth.NewSFCBridgeObserver(request.BcID, request.SFCAddr, sfc, s, end)
 			if err != nil {
 				logging.Error(err.Error())
 				return
 			}
-			logging.Info("Start observing contract %v.", request.SFCAddr)
-			for {
-				select {
-				case log := <-event.Err():
-					logging.Error(log.Error())
-					return
-				case call := <-sink:
-					// Pack & Send to message queue.
-					logging.Info("Event observed: %v.", call)
-					data, err := json.Marshal(call.Raw)
-					if err != nil {
-						logging.Error(err.Error())
-						return
-					}
-					msg := &v1.Message{
-						ID:        "TBD", //TODO
-						Timestamp: call.Timestamp.Int64(),
-						MsgType:   v1.MessageType,
-						Version:   v1.Version,
-						Destination: v1.ApplicationAddress{
-							NetworkID:       call.DestBcId.String(),
-							ContractAddress: call.DestContract.String(),
-						},
-						Source: v1.ApplicationAddress{
-							NetworkID:       request.BcID,
-							ContractAddress: request.SFCAddr,
-						},
-						Proofs:  []v1.Proof{},
-						Payload: hex.EncodeToString(data),
-					}
-					s.Request(v1.Version, v1.MessageType, msg)
-					logging.Info("Event processed.")
-				case <-end:
-					logging.Info("Stop observing contract %v.", request.SFCAddr)
-				}
-			}
+			observer.Start()
 		}()
 		return []byte{0}, nil
 	}
diff --git a/messaging/relayer/internal/msgobserver/eth/event_transformer.go b/messaging/relayer/internal/msgobserver/eth/event_transformer.go
index 9a22bd55..f2304176 100644
--- a/messaging/relayer/internal/msgobserver/eth/event_transformer.go
+++ b/messaging/relayer/internal/msgobserver/eth/event_transformer.go
@@ -17,6 +17,7 @@ package eth
 
 import (
 	"encoding/hex"
+	"encoding/json"
 	"errors"
 	"fmt"
 
@@ -31,7 +32,8 @@ type EventTransformer interface {
 
 // SFCEventTransformer converts events from a simple-function-call bridge contract to relayer messages
 type SFCEventTransformer struct {
-	Source string
+	Source     string
+	SourceAddr string
 }
 
 // ToMessage converts a 'CrossCall' event emited from a simple-function-call bridge contract to relayer message
@@ -44,9 +46,14 @@ func (t *SFCEventTransformer) ToMessage(event interface{}) (*v1.Message, error)
 		return nil, err
 	}
 
-	source := v1.ApplicationAddress{NetworkID: t.Source, ContractAddress: sfcEvent.DestContract.String()}
+	source := v1.ApplicationAddress{NetworkID: t.Source, ContractAddress: t.SourceAddr}
 	destination := v1.ApplicationAddress{NetworkID: sfcEvent.DestBcId.String(), ContractAddress: sfcEvent.DestContract.String()}
 
+	data, err := json.Marshal(sfcEvent.Raw)
+	if err != nil {
+		return nil, err
+	}
+
 	message := v1.Message{
 		ID:          hex.EncodeToString(randomBytes(16)), // TODO: replace with a proper message id scheme
 		Timestamp:   sfcEvent.Timestamp.Int64(),
@@ -54,7 +61,8 @@ func (t *SFCEventTransformer) ToMessage(event interface{}) (*v1.Message, error)
 		Version:     v1.Version,
 		Destination: destination,
 		Source:      source,
-		Payload:     toBase64String(sfcEvent.DestFunctionCall),
+		Proofs:      []v1.Proof{},
+		Payload:     hex.EncodeToString(data),
 	}
 
 	return &message, nil
@@ -72,6 +80,6 @@ func (t *SFCEventTransformer) validate(event *functioncall.SfcCrossCall) error {
 	return nil
 }
 
-func NewSFCEventTransformer(sourceNetwork string) *SFCEventTransformer {
-	return &SFCEventTransformer{sourceNetwork}
+func NewSFCEventTransformer(sourceNetwork string, sourceAddr string) *SFCEventTransformer {
+	return &SFCEventTransformer{sourceNetwork, sourceAddr}
 }
diff --git a/messaging/relayer/internal/msgobserver/eth/event_transformer_test.go b/messaging/relayer/internal/msgobserver/eth/event_transformer_test.go
index 548388a3..4ea87fd6 100644
--- a/messaging/relayer/internal/msgobserver/eth/event_transformer_test.go
+++ b/messaging/relayer/internal/msgobserver/eth/event_transformer_test.go
@@ -16,6 +16,8 @@ package eth
  */
 
 import (
+	"encoding/hex"
+	"encoding/json"
 	"math/big"
 	"testing"
 
@@ -30,16 +32,19 @@ var fixValidEvent = functioncall.SfcCrossCall{
 	Timestamp:        big.NewInt(1639527190),
 	DestFunctionCall: randomBytes(10),
 }
-var transformer = NewSFCEventTransformer("network-001")
+var transformer = NewSFCEventTransformer("network-001", "0x8e215d06ea7ec1fdb4fc5fd21768f4b34ee92ef4")
 
 func TestSFCTransformer(t *testing.T) {
 	message, err := transformer.ToMessage(&fixValidEvent)
 	assert.Nil(t, err)
 
+	data, err := json.Marshal(fixValidEvent.Raw)
+	assert.Nil(t, err)
+
 	assert.Equal(t, fixValidEvent.DestBcId.String(), message.Destination.NetworkID)
 	assert.Equal(t, fixValidEvent.DestContract.String(), message.Destination.ContractAddress)
 	assert.Equal(t, fixValidEvent.Timestamp, big.NewInt(message.Timestamp))
-	assert.Equal(t, toBase64String(fixValidEvent.DestFunctionCall), message.Payload)
+	assert.Equal(t, hex.EncodeToString(data), message.Payload)
 }
 func TestSFCTransformerFailsOnInvalidEventType(t *testing.T) {
 	assert.Panics(t, func() { transformer.ToMessage("invalid event") })
diff --git a/messaging/relayer/internal/msgobserver/eth/event_watcher.go b/messaging/relayer/internal/msgobserver/eth/event_watcher.go
index 3afe8047..176faa11 100644
--- a/messaging/relayer/internal/msgobserver/eth/event_watcher.go
+++ b/messaging/relayer/internal/msgobserver/eth/event_watcher.go
@@ -20,6 +20,7 @@ import (
 	"log"
 
 	"github.com/consensys/gpact/messaging/relayer/internal/contracts/functioncall"
+	"github.com/consensys/gpact/messaging/relayer/internal/logging"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/event"
 )
@@ -39,6 +40,8 @@ type EventWatcherConfig struct {
 type SFCCrossCallWatcher struct {
 	EventWatcherConfig
 	SfcContract *functioncall.Sfc
+
+	end chan bool
 }
 
 // Watch subscribes and starts listening to 'CrossCall' events from a given simple-function-call contract.
@@ -55,17 +58,21 @@ func (l *SFCCrossCallWatcher) Watch() {
 }
 
 func (l *SFCCrossCallWatcher) start(sub event.Subscription, chanEvents <-chan *functioncall.SfcCrossCall) {
+	logging.Info("Start watching %v...", l.SfcContract)
 	for {
 		select {
 		case err := <-sub.Err():
 			// TODO: communicate this to the calling context
-			log.Fatalf("error in log subscription %v", err)
+			logging.Error("error in log subscription %v", err)
 		case log := <-chanEvents:
 			l.Handler.Handle(log)
+		case <-l.end:
+			logging.Info("Stop watching %v.", l.SfcContract)
+			return
 		}
 	}
 }
 
-func NewSFCCrossCallWatcher(context context.Context, handler EventHandler, contract *functioncall.Sfc) *SFCCrossCallWatcher {
-	return &SFCCrossCallWatcher{EventWatcherConfig: EventWatcherConfig{Context: context, Handler: handler}, SfcContract: contract}
+func NewSFCCrossCallWatcher(context context.Context, handler EventHandler, contract *functioncall.Sfc, end chan bool) *SFCCrossCallWatcher {
+	return &SFCCrossCallWatcher{EventWatcherConfig: EventWatcherConfig{Context: context, Handler: handler}, SfcContract: contract, end: end}
 }
diff --git a/messaging/relayer/internal/msgobserver/eth/event_watcher_test.go b/messaging/relayer/internal/msgobserver/eth/event_watcher_test.go
index b7b6086e..113a5dd6 100644
--- a/messaging/relayer/internal/msgobserver/eth/event_watcher_test.go
+++ b/messaging/relayer/internal/msgobserver/eth/event_watcher_test.go
@@ -39,7 +39,7 @@ func TestSFCCrossCallWatcher(t *testing.T) {
 	handler := new(MockEventHandler)
 	handler.On("Handle", mock.AnythingOfType("*functioncall.SfcCrossCall")).Once().Return(nil)
 
-	watcher := NewSFCCrossCallWatcher(auth.Context, handler, contract)
+	watcher := NewSFCCrossCallWatcher(auth.Context, handler, contract, make(chan bool))
 	go watcher.Watch()
 
 	_, err := contract.SfcTransactor.CrossBlockchainCall(auth, big.NewInt(100), auth.From, []byte("payload"))
diff --git a/messaging/relayer/internal/msgobserver/eth/message_observer.go b/messaging/relayer/internal/msgobserver/eth/message_observer.go
index f6b42e9b..dd2f7131 100644
--- a/messaging/relayer/internal/msgobserver/eth/message_observer.go
+++ b/messaging/relayer/internal/msgobserver/eth/message_observer.go
@@ -30,11 +30,11 @@ type SFCBridgeObserver struct {
 	SourceNetwork string
 }
 
-func NewSFCBridgeObserver(source string, contract *functioncall.Sfc, mq mqserver.MessageQueue) (*SFCBridgeObserver, error) {
-	eventTransformer := NewSFCEventTransformer(source)
+func NewSFCBridgeObserver(source string, sourceAddr string, contract *functioncall.Sfc, mq mqserver.MessageQueue, end chan bool) (*SFCBridgeObserver, error) {
+	eventTransformer := NewSFCEventTransformer(source, sourceAddr)
 	messageHandler := NewMessageEnqueueHandler(mq)
 	eventHandler := NewSimpleEventHandler(eventTransformer, messageHandler)
-	eventWatcher := NewSFCCrossCallWatcher(context.Background(), eventHandler, contract)
+	eventWatcher := NewSFCCrossCallWatcher(context.Background(), eventHandler, contract, end)
 
 	return &SFCBridgeObserver{EventWatcher: eventWatcher, EventHandler: eventHandler, SourceNetwork: source}, nil
 }
diff --git a/messaging/relayer/internal/msgobserver/eth/message_observer_test.go b/messaging/relayer/internal/msgobserver/eth/message_observer_test.go
index b130c0a5..ac15fb2e 100644
--- a/messaging/relayer/internal/msgobserver/eth/message_observer_test.go
+++ b/messaging/relayer/internal/msgobserver/eth/message_observer_test.go
@@ -30,12 +30,13 @@ func TestSFCBridgeObserver(t *testing.T) {
 	fixDesAddress := common.HexToAddress("0x8e215d06ea7ec1fdb4fc5fd21768f4b34ee92ef4")
 	fixDestID := big.NewInt(2)
 	fixSourceID := "1"
+	fixSourceAddress := "0x8e215d06ea7ec1fdb4fc5fd21768f4b34ee92ef4"
 
 	simBackend, auth := simulatedBackend(t)
 	contract := deployContract(t, simBackend, auth)
 	mockMQ := new(MockMQ)
 
-	observer, err := NewSFCBridgeObserver(fixSourceID, contract, mockMQ)
+	observer, err := NewSFCBridgeObserver(fixSourceID, fixSourceAddress, contract, mockMQ, make(chan bool))
 	assert.Nil(t, err)
 	go observer.Start()