diff --git a/appPublic/across_nat.py b/appPublic/across_nat.py
new file mode 100644
index 0000000..33beec7
--- /dev/null
+++ b/appPublic/across_nat.py
@@ -0,0 +1,158 @@
+
+from natpmp import NATPMP as pmp
+from aioupnp.upnp import UPnP
+from requests import get
+from .background import Background
+
+class AcrossNat(object):
+	def __init__(self):
+		self.external_ip = None
+		self.upnp = None
+		self.pmp_supported = True
+		self.upnp_supported = True
+		self.init_pmp()
+
+	async def init_upnp(self):
+		if self.upnp is None:
+			self.upnp = await UPnP.discover()
+
+	def init_pmp(self):
+		try:
+			self.external_ip = pmp.get_public_address()
+		except pmp.NATPMPUnsupportedError:
+			self.pmp_supported = False
+
+	def init_upnp(self):
+		try:
+			self.upnp = UPnP()
+			devices = self.upnp.discover()
+			if len(devices) == 0:
+				self.upnp_supported = False
+		except:
+			self.upnp_supported = False
+
+	async def get_external_ip(self):
+		if self.pmp_supported:
+			return self._pmp_get_external_ip()
+
+		if self.upnp_supported:
+			return await self.upnp.get_external_ip()
+
+		try:
+			return get('https://api.ipify.org').text
+		except:
+			return get('https://ipapi.co/ip/').text
+
+
+	def _pmp_get_external_ip(self):
+		return pmp.get_public_address()
+
+	def _upnp_get_external_ip(self):
+		
+	await def upnp_map_port(inner_port, protocol='TCP', from_port=40003):
+		protocol = protocol.upper()
+		external_port = from_port
+		while external_port < 52333:
+			x = await self.upnp.get_specific_port_mapping(external_port, protocol)
+			if len(x) == 0:
+				break
+			external_port += 1
+
+		if external_port < 52333:
+			await self.upnp.add_port_mapping(external_port,
+									protocol,
+									inner_port,
+									lan_address,
+									desc or 'user added')
+			return external_port
+		return None
+
+	async def is_port_mapped(self, external_port, protocol='TCP'):
+		protocol = protocol.upper()
+		if self.upnp_supported:
+			x = await self.upnp.get_specific_port_mapping(external_port, 
+									protocol)
+			if len(x) == 0:
+				return True
+			return False
+		raise Exception('not implemented')
+
+	async def port_unmap(self, external_port, protocol='TCP'):
+		protocol = protocol.upper()
+		if self.upnp_supported:
+			await self.upnp.delete_port_mapping(external_port, protocol)
+		raise Exception('not implemented')
+
+	def map_port(self, inner_port, protocol='tcp', from_port=40003):
+		if pmp_supported:
+			return _map_port(inner_port, protocol=protocol)
+
+		return self.upnp.add_port_mapping(
+			
+			inner_port, protocol=protocol)
+
+
+
+pmp_supported = True
+
+"""
+_natmap mapping a localhost port to network gateway outter ip's port
+input:
+	port: integer, localhost host port
+	protocal: string, 'tcp', or 'udp', default is 'tcp'
+	from_port: integer, the return port will from this prot, 
+				default is 49000, if mapping failed, increases by one, 
+				and try it again. 
+
+return:
+	gateway outter ip's port, if gateway not support natpmp, return None
+"""
+
+def pmp_getExtenalIPAddress():
+	return pmp.get_public_address()
+
+
+
+def get_external_ip():
+	global pmp_supported
+	if pmp_supported:
+		try:
+			return pmp_get_public_address()
+		except pmp.NATPMPUnsupportedError:
+			pmp_supported = False
+		except Exception as e:
+			raise e
+	upnp = UPnP()
+	devices = upnp.discover()
+	if len(devices) < 1:
+		return None
+	d = devices[0]
+	services = d.get_services()
+
+def _pmp_natmap(innerport, 
+			protocol='tcp', 
+			from_port=49000, 
+			timeout=3600):
+	gateway = pmp.get_gateway_addr()
+	ret_port = from_port
+	while 1:
+		try:
+			mode = pmp.NATPMP_PROTOCOL_TCP
+			if protocol != 'tcp':
+				mode = pmp.NATPMP_PROTOCOL_UDP
+
+			x = pmp.map_port(mode, 
+						ret_port, 
+						innerport, 
+						timeout, 
+						gateway_ip=gateway)
+			return x.public_port
+		except pmp.NATPMPUnsupportedError:
+			return None
+		except Exception, e:
+			time.sleep(0.01)
+			ret_port+=1
+			if ret_port > 60000:
+				return None
+
+def natmap(
diff --git a/requirements.txt b/requirements.txt
index e4eaf90..9af24b6 100755
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,6 +7,7 @@ numpy
 cryptography
 brotli
 aiohttp
+aioupnp
 asyncio 
 requests
 jinja2