diff --git a/networks/tor/BaseOnionService.go b/networks/tor/BaseOnionService.go
index c6a30a8..37e7cf9 100644
--- a/networks/tor/BaseOnionService.go
+++ b/networks/tor/BaseOnionService.go
@@ -21,6 +21,27 @@ type BaseOnionService struct {
 	privateKey  ed25519.PrivateKey
 	ls          connectivity.ListenService
 	lock        sync.Mutex
+	port        int
+}
+
+// Metrics provides a report of useful information about the status of the service e.g. the number of active
+// connections
+func (s *BaseOnionService) Metrics() tapir.ServiceMetrics {
+	s.lock.Lock()
+	defer s.lock.Unlock()
+
+	count := 0
+	s.connections.Range(func(key, value interface{}) bool {
+		connection := value.(tapir.Connection)
+		if !connection.IsClosed() {
+			count++
+		}
+		return true
+	})
+
+	return tapir.ServiceMetrics{
+		ConnectionCount: count,
+	}
 }
 
 // Metrics provide metrics for services
@@ -50,6 +71,12 @@ func (s *BaseOnionService) Init(acn connectivity.ACN, sk ed25519.PrivateKey, id
 	s.acn = acn
 	s.id = id
 	s.privateKey = sk
+	s.port = 9878
+}
+
+// SetPort configures the port that the service uses.
+func (s *BaseOnionService) SetPort(port int) {
+	s.port = port
 }
 
 // WaitForCapabilityOrClose blocks until the connection has the given capability or the underlying connection is closed
@@ -145,7 +172,7 @@ func (s *BaseOnionService) Listen(app tapir.Application) error {
 	// accepts a new connection
 	// spins off to a connection struct
 	s.lock.Lock()
-	ls, err := s.acn.Listen(s.privateKey, 9878)
+	ls, err := s.acn.Listen(s.privateKey, s.port)
 	s.ls = ls
 	log.Debugf("Starting a service on %v ", ls.AddressFull())
 	s.lock.Unlock()
@@ -171,7 +198,9 @@ func (s *BaseOnionService) Listen(app tapir.Application) error {
 func (s *BaseOnionService) Shutdown() {
 	s.lock.Lock()
 	defer s.lock.Unlock()
-	s.ls.Close()
+	if s.ls != nil {
+		s.ls.Close()
+	}
 	s.connections.Range(func(key, value interface{}) bool {
 		connection := value.(tapir.Connection)
 		connection.Close()
diff --git a/primitives/privacypass/token.go b/primitives/privacypass/token.go
index e4ffc0d..e7ce557 100644
--- a/primitives/privacypass/token.go
+++ b/primitives/privacypass/token.go
@@ -72,7 +72,8 @@ func (t *Token) unblindSignedToken(token SignedToken) {
 func (t *Token) SpendToken(data []byte) SpentToken {
 	key := sha3.Sum256(append(t.t, t.W.Encode(nil)...))
 	mac := hmac.New(sha3.New512, key[:])
-	return SpentToken{t.t, mac.Sum(data)}
+	mac.Write(data)
+	return SpentToken{t.t, mac.Sum(nil)}
 }
 
 // GenerateBlindedTokenBatch generates a batch of blinded tokens (and their unblinded equivalents)
diff --git a/primitives/privacypass/tokenserver.go b/primitives/privacypass/tokenserver.go
index 72a279b..7559a77 100644
--- a/primitives/privacypass/tokenserver.go
+++ b/primitives/privacypass/tokenserver.go
@@ -136,7 +136,8 @@ func (ts *TokenServer) SpendToken(token SpentToken, data []byte) error {
 	W := new(ristretto.Element).ScalarMult(ts.k, T)
 	key := sha3.Sum256(append(token.T, W.Encode(nil)...))
 	mac := hmac.New(sha3.New512, key[:])
-	computedMAC := mac.Sum(data)
+	mac.Write(data)
+	computedMAC := mac.Sum(nil)
 	result := hmac.Equal(token.MAC, computedMAC)
 	if result == true {
 		if ts.persistanceService == nil {
diff --git a/scratch/main.go b/scratch/main.go
new file mode 100644
index 0000000..e69de29
diff --git a/service.go b/service.go
index 2ba5d65..e971ae8 100644
--- a/service.go
+++ b/service.go
@@ -12,7 +12,8 @@ import (
 	"sync"
 )
 
-// ServiceMetrics are metrics for servers...
+
+// ServiceMetrics outlines higher level information about the service e.g. counts of connections
 type ServiceMetrics struct {
 	ConnectionCount int
 }