@@ -248,12 +248,12 @@ type PortMapper struct {

 }

 func (mapper *PortMapper) Map(ip net.IP, port int, backendAddr net.Addr) error {

-	mapKey := (&net.TCPAddr{Port: port, IP: ip}).String()

-	if _, exists := mapper.tcpProxies[mapKey]; exists {

-		return fmt.Errorf("Port %s is already in use", mapKey)

-	}

 	if _, isTCP := backendAddr.(*net.TCPAddr); isTCP {

+		mapKey := (&net.TCPAddr{Port: port, IP: ip}).String()

+		if _, exists := mapper.tcpProxies[mapKey]; exists {

+			return fmt.Errorf("TCP Port %s is already in use", mapKey)

+		}

 		backendPort := backendAddr.(*net.TCPAddr).Port

 		backendIP := backendAddr.(*net.TCPAddr).IP

 		if mapper.iptables != nil {

@@ -270,6 +270,10 @@ func (mapper *PortMapper) Map(ip net.IP, port int, backendAddr net.Addr) error {

 		mapper.tcpProxies[mapKey] = proxy

 		go proxy.Run()

 	} else {

+		mapKey := (&net.UDPAddr{Port: port, IP: ip}).String()

+		if _, exists := mapper.udpProxies[mapKey]; exists {

+			return fmt.Errorf("UDP: Port %s is already in use", mapKey)

+		}

 		backendPort := backendAddr.(*net.UDPAddr).Port

 		backendIP := backendAddr.(*net.UDPAddr).IP

 		if mapper.iptables != nil {

@@ -290,8 +294,8 @@ func (mapper *PortMapper) Map(ip net.IP, port int, backendAddr net.Addr) error {

 }

 func (mapper *PortMapper) Unmap(ip net.IP, port int, proto string) error {

-	mapKey := (&net.TCPAddr{Port: port, IP: ip}).String()

 	if proto == "tcp" {

+		mapKey := (&net.TCPAddr{Port: port, IP: ip}).String()

 		backendAddr, ok := mapper.tcpMapping[mapKey]

 		if !ok {

 			return fmt.Errorf("Port tcp/%s is not mapped", mapKey)

@@ -307,6 +311,7 @@ func (mapper *PortMapper) Unmap(ip net.IP, port int, proto string) error {

 		}

 		delete(mapper.tcpMapping, mapKey)

 	} else {

+		mapKey := (&net.UDPAddr{Port: port, IP: ip}).String()

 		backendAddr, ok := mapper.udpMapping[mapKey]

 		if !ok {

 			return fmt.Errorf("Port udp/%s is not mapped", mapKey)