diff --git a/internal/port/port.go b/internal/port/port.go
index 6512f40..68e185a 100644
--- a/internal/port/port.go
+++ b/internal/port/port.go
@@ -9,36 +9,47 @@ import (
 	"tunnel_pls/utils"
 )
 
-type PortManager struct {
+type Manager interface {
+	AddPortRange(startPort, endPort uint16) error
+	GetUnassignedPort() (uint16, bool)
+	SetPortStatus(port uint16, assigned bool) error
+	GetPortStatus(port uint16) (bool, bool)
+}
+
+type manager struct {
 	mu          sync.RWMutex
 	ports       map[uint16]bool
 	sortedPorts []uint16
 }
 
-var Manager = PortManager{
+var Default Manager = &manager{
 	ports:       make(map[uint16]bool),
 	sortedPorts: []uint16{},
 }
 
 func init() {
-	rawRange := utils.Getenv("ALLOWED_PORTS", "40000-41000")
+	rawRange := utils.Getenv("ALLOWED_PORTS", "")
+	if rawRange == "" {
+		return
+	}
+
 	splitRange := strings.Split(rawRange, "-")
 	if len(splitRange) != 2 {
-		Manager.AddPortRange(30000, 31000)
-	} else {
-		start, err := strconv.ParseUint(splitRange[0], 10, 16)
-		if err != nil {
-			start = 30000
-		}
-		end, err := strconv.ParseUint(splitRange[1], 10, 16)
-		if err != nil {
-			end = 31000
-		}
-		Manager.AddPortRange(uint16(start), uint16(end))
+		return
 	}
+
+	start, err := strconv.ParseUint(splitRange[0], 10, 16)
+	if err != nil {
+		return
+	}
+	end, err := strconv.ParseUint(splitRange[1], 10, 16)
+	if err != nil {
+		return
+	}
+	_ = Default.AddPortRange(uint16(start), uint16(end))
 }
 
-func (pm *PortManager) AddPortRange(startPort, endPort uint16) error {
+func (pm *manager) AddPortRange(startPort, endPort uint16) error {
 	pm.mu.Lock()
 	defer pm.mu.Unlock()
 
@@ -57,7 +68,7 @@ func (pm *PortManager) AddPortRange(startPort, endPort uint16) error {
 	return nil
 }
 
-func (pm *PortManager) GetUnassignedPort() (uint16, bool) {
+func (pm *manager) GetUnassignedPort() (uint16, bool) {
 	pm.mu.Lock()
 	defer pm.mu.Unlock()
 
@@ -70,7 +81,7 @@ func (pm *PortManager) GetUnassignedPort() (uint16, bool) {
 	return 0, false
 }
 
-func (pm *PortManager) SetPortStatus(port uint16, assigned bool) error {
+func (pm *manager) SetPortStatus(port uint16, assigned bool) error {
 	pm.mu.Lock()
 	defer pm.mu.Unlock()
 
@@ -78,7 +89,7 @@ func (pm *PortManager) SetPortStatus(port uint16, assigned bool) error {
 	return nil
 }
 
-func (pm *PortManager) GetPortStatus(port uint16) (bool, bool) {
+func (pm *manager) GetPortStatus(port uint16) (bool, bool) {
 	pm.mu.RLock()
 	defer pm.mu.RUnlock()
 
diff --git a/session/handler.go b/session/handler.go
index eb61cfd..d536b51 100644
--- a/session/handler.go
+++ b/session/handler.go
@@ -107,7 +107,7 @@ func (s *SSHSession) HandleTCPIPForward(req *ssh.Request) {
 		return
 	} else {
 		if portToBind == 0 {
-			unassign, success := portUtil.Manager.GetUnassignedPort()
+			unassign, success := portUtil.Default.GetUnassignedPort()
 			portToBind = unassign
 			if !success {
 				s.Interaction.SendMessage("No available port\r\n")
@@ -122,7 +122,7 @@ func (s *SSHSession) HandleTCPIPForward(req *ssh.Request) {
 				}
 				return
 			}
-		} else if isUse, isExist := portUtil.Manager.GetPortStatus(portToBind); isExist && isUse {
+		} else if isUse, isExist := portUtil.Default.GetPortStatus(portToBind); isExist && isUse {
 			s.Interaction.SendMessage(fmt.Sprintf("Port %d is already in use or restricted. Please choose a different port. (03)\r\n", portToBind))
 			err := req.Reply(false, nil)
 			if err != nil {
@@ -135,7 +135,7 @@ func (s *SSHSession) HandleTCPIPForward(req *ssh.Request) {
 			}
 			return
 		}
-		err := portUtil.Manager.SetPortStatus(portToBind, true)
+		err := portUtil.Default.SetPortStatus(portToBind, true)
 		if err != nil {
 			log.Println("Failed to set port status:", err)
 			return
@@ -208,7 +208,7 @@ func (s *SSHSession) HandleTCPForward(req *ssh.Request, addr string, portToBind
 	listener, err := net.Listen("tcp", fmt.Sprintf("0.0.0.0:%d", portToBind))
 	if err != nil {
 		s.Interaction.SendMessage(fmt.Sprintf("Port %d is already in use or restricted. Please choose a different port.\r\n", portToBind))
-		if setErr := portUtil.Manager.SetPortStatus(portToBind, false); setErr != nil {
+		if setErr := portUtil.Default.SetPortStatus(portToBind, false); setErr != nil {
 			log.Printf("Failed to reset port status: %v", setErr)
 		}
 		err = req.Reply(false, nil)
@@ -227,7 +227,7 @@ func (s *SSHSession) HandleTCPForward(req *ssh.Request, addr string, portToBind
 	err = binary.Write(buf, binary.BigEndian, uint32(portToBind))
 	if err != nil {
 		log.Println("Failed to write port to buffer:", err)
-		if setErr := portUtil.Manager.SetPortStatus(portToBind, false); setErr != nil {
+		if setErr := portUtil.Default.SetPortStatus(portToBind, false); setErr != nil {
 			log.Printf("Failed to reset port status: %v", setErr)
 		}
 		err = listener.Close()
@@ -242,7 +242,7 @@ func (s *SSHSession) HandleTCPForward(req *ssh.Request, addr string, portToBind
 	err = req.Reply(true, buf.Bytes())
 	if err != nil {
 		log.Println("Failed to reply to request:", err)
-		if setErr := portUtil.Manager.SetPortStatus(portToBind, false); setErr != nil {
+		if setErr := portUtil.Default.SetPortStatus(portToBind, false); setErr != nil {
 			log.Printf("Failed to reset port status: %v", setErr)
 		}
 		err = listener.Close()
diff --git a/session/lifecycle/lifecycle.go b/session/lifecycle/lifecycle.go
index ecfc206..11106f8 100644
--- a/session/lifecycle/lifecycle.go
+++ b/session/lifecycle/lifecycle.go
@@ -85,7 +85,7 @@ func (l *Lifecycle) Close() error {
 	}
 
 	if l.Forwarder.GetTunnelType() == types.TCP {
-		err := portUtil.Manager.SetPortStatus(l.Forwarder.GetForwardedPort(), false)
+		err := portUtil.Default.SetPortStatus(l.Forwarder.GetForwardedPort(), false)
 		if err != nil {
 			return err
 		}