pep8 reformatted

19 files changed, 107 insertions, 52 deletions

diff --git a/pysnmp/carrier/asyncio/base.py b/pysnmp/carrier/asyncio/base.py
index 002239bb..217092a6 100644
--- a/pysnmp/carrier/asyncio/base.py
+++ b/pysnmp/carrier/asyncio/base.py
@@ -33,6 +33,7 @@
 from pysnmp.carrier.asyncio.dispatch import AsyncioDispatcher
 from pysnmp.carrier.base import AbstractTransport
 
+
 class AbstractAsyncioTransport(AbstractTransport):
     protoTransportDispatcher = AsyncioDispatcher
     """Base Asyncio Transport, to be used with AsyncioDispatcher"""
diff --git a/pysnmp/carrier/asyncio/dgram/base.py b/pysnmp/carrier/asyncio/dgram/base.py
index 5c3b78b6..3abcc3a3 100644
--- a/pysnmp/carrier/asyncio/dgram/base.py
+++ b/pysnmp/carrier/asyncio/dgram/base.py
@@ -35,6 +35,7 @@ import traceback
 from pysnmp.carrier.asyncio.base import AbstractAsyncioTransport
 from pysnmp.carrier import error
 from pysnmp import debug
+
 try:
     import asyncio
 except ImportError:
@@ -42,14 +43,16 @@ except ImportError:
 
 loop = asyncio.get_event_loop()
 
+
 class DgramAsyncioProtocol(asyncio.DatagramProtocol, AbstractAsyncioTransport):
     """Base Asyncio datagram Transport, to be used with AsyncioDispatcher"""
     sockFamily = None
     addressType = lambda x: x
     transport = None
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, sock=None, sockMap=None):
         self._writeQ = []
+        self._lport = None
 
     def datagram_received(self, datagram, transportAddress):
         if self._cbFun is None:
@@ -95,7 +98,8 @@ class DgramAsyncioProtocol(asyncio.DatagramProtocol, AbstractAsyncioTransport):
         return self
 
     def closeTransport(self):
-        self._lport.cancel()
+        if self._lport is not None:
+            self._lport.cancel()
         if self.transport is not None:
             self.transport.close()
         AbstractAsyncioTransport.closeTransport(self)
diff --git a/pysnmp/carrier/asyncio/dgram/udp.py b/pysnmp/carrier/asyncio/dgram/udp.py
index aa73fb10..f80de36b 100644
--- a/pysnmp/carrier/asyncio/dgram/udp.py
+++ b/pysnmp/carrier/asyncio/dgram/udp.py
@@ -33,6 +33,7 @@
 import socket
 from pysnmp.carrier.base import AbstractTransportAddress
 from pysnmp.carrier.asyncio.dgram.base import DgramAsyncioProtocol
+
 try:
     import asyncio
 except ImportError:
@@ -42,11 +43,14 @@ loop = asyncio.get_event_loop()
 
 domainName = snmpUDPDomain = (1, 3, 6, 1, 6, 1, 1)
 
+
 class UdpTransportAddress(tuple, AbstractTransportAddress):
     pass
 
+
 class UdpAsyncioTransport(DgramAsyncioProtocol):
     sockFamily = socket.AF_INET
     addressType = UdpTransportAddress
 
+
 UdpTransport = UdpAsyncioTransport
diff --git a/pysnmp/carrier/asyncio/dgram/udp6.py b/pysnmp/carrier/asyncio/dgram/udp6.py
index ad3c28dd..290c03bd 100644
--- a/pysnmp/carrier/asyncio/dgram/udp6.py
+++ b/pysnmp/carrier/asyncio/dgram/udp6.py
@@ -7,6 +7,7 @@
 import socket
 from pysnmp.carrier.base import AbstractTransportAddress
 from pysnmp.carrier.asyncio.dgram.base import DgramAsyncioProtocol
+
 try:
     import asyncio
 except ImportError:
@@ -16,9 +17,11 @@ loop = asyncio.get_event_loop()
 
 domainName = snmpUDP6Domain = (1, 3, 6, 1, 2, 1, 100, 1, 2)
 
+
 class Udp6TransportAddress(tuple, AbstractTransportAddress):
     pass
 
+
 class Udp6AsyncioTransport(DgramAsyncioProtocol):
     sockFamily = socket.has_ipv6 and socket.AF_INET6 or None
     addressType = Udp6TransportAddress
@@ -28,9 +31,10 @@ class Udp6AsyncioTransport(DgramAsyncioProtocol):
             return self.addressType((transportAddress[0].split('%')[0],
                                      transportAddress[1],
                                      0,  # flowinfo
-                                     0)) # scopeid
+                                     0))  # scopeid
         else:
             return self.addressType((transportAddress[0],
                                      transportAddress[1], 0, 0))
 
+
 Udp6Transport = Udp6AsyncioTransport
diff --git a/pysnmp/carrier/asyncio/dispatch.py b/pysnmp/carrier/asyncio/dispatch.py
index 0cfa4ceb..cb4c0941 100644
--- a/pysnmp/carrier/asyncio/dispatch.py
+++ b/pysnmp/carrier/asyncio/dispatch.py
@@ -34,6 +34,7 @@ import sys
 import traceback
 from pysnmp.carrier.base import AbstractTransportDispatcher
 from pysnmp.error import PySnmpError
+
 try:
     import asyncio
 except ImportError:
@@ -41,8 +42,10 @@ except ImportError:
 
 loop = asyncio.get_event_loop()
 
+
 class AsyncioDispatcher(AbstractTransportDispatcher):
     """AsyncioDispatcher based on asyncio event loop"""
+
     def __init__(self, *args, **kwargs):
         AbstractTransportDispatcher.__init__(self)
         self.__transportCount = 0
@@ -70,7 +73,7 @@ class AsyncioDispatcher(AbstractTransportDispatcher):
             self.loopingcall = asyncio.async(self.handle_timeout())
         AbstractTransportDispatcher.registerTransport(
             self, tDomain, transport
-            )
+        )
         self.__transportCount += 1
 
     def unregisterTransport(self, tDomain):
@@ -84,9 +87,10 @@ class AsyncioDispatcher(AbstractTransportDispatcher):
             self.loopingcall.cancel()
             self.loopingcall = None
 
+
 # Trollius or Tulip?
 if not hasattr(asyncio, "From"):
-    exec("""\
+    exec ("""\
 @asyncio.coroutine
 def handle_timeout(self):
     while True:
@@ -94,4 +98,3 @@ def handle_timeout(self):
         self.handleTimerTick(loop.time())
 AsyncioDispatcher.handle_timeout = handle_timeout\
 """)
-
diff --git a/pysnmp/carrier/asyncore/base.py b/pysnmp/carrier/asyncore/base.py
index da68774d..04044775 100644
--- a/pysnmp/carrier/asyncore/base.py
+++ b/pysnmp/carrier/asyncore/base.py
@@ -4,13 +4,15 @@
 # Copyright (c) 2005-2016, Ilya Etingof <ilya@glas.net>
 # License: http://pysnmp.sf.net/license.html
 #
-import socket, sys
+import socket
+import sys
 import asyncore
 from pysnmp.carrier import error
 from pysnmp.carrier.base import AbstractTransport
 from pysnmp.carrier.asyncore.dispatch import AsyncoreDispatcher
 from pysnmp import debug
 
+
 class AbstractSocketTransport(asyncore.dispatcher, AbstractTransport):
     protoTransportDispatcher = AsyncoreDispatcher
     sockFamily = sockType = None
@@ -25,11 +27,11 @@ class AbstractSocketTransport(asyncore.dispatcher, AbstractTransport):
             if self.sockFamily is None:
                 raise error.CarrierError(
                     'Address family %s not supported' % self.__class__.__name__
-                    )
+                )
             if self.sockType is None:
                 raise error.CarrierError(
                     'Socket type %s not supported' % self.__class__.__name__
-                    )
+                )
             try:
                 sock = socket.socket(self.sockFamily, self.sockType)
             except socket.error:
@@ -42,7 +44,7 @@ class AbstractSocketTransport(asyncore.dispatcher, AbstractTransport):
                         sock.setsockopt(socket.SOL_SOCKET, b, self.bufferSize)
                         debug.logger & debug.flagIO and debug.logger('%s: socket %d buffer size increased from %d to %d for buffer %d' % (self.__class__.__name__, sock.fileno(), bsize, self.bufferSize, b))
             except Exception:
-                debug.logger & debug.flagIO and debug.logger('%s: socket buffer size option mangling failure for buffer %d: %s' % (self.__class__.__name__, b, sys.exc_info()[1]))
+                debug.logger & debug.flagIO and debug.logger('%s: socket buffer size option mangling failure for buffer: %s' % (self.__class__.__name__, sys.exc_info()[1]))
 
         # The socket map is managed by the AsyncoreDispatcher on
         # which this transport is registered. Here we just prepare
diff --git a/pysnmp/carrier/asyncore/dgram/base.py b/pysnmp/carrier/asyncore/dgram/base.py
index c64b7e89..49b7846e 100644
--- a/pysnmp/carrier/asyncore/dgram/base.py
+++ b/pysnmp/carrier/asyncore/dgram/base.py
@@ -4,7 +4,9 @@
 # Copyright (c) 2005-2016, Ilya Etingof <ilya@glas.net>
 # License: http://pysnmp.sf.net/license.html
 #
-import socket, errno, sys
+import socket
+import errno
+import sys
 from pysnmp.carrier.asyncore.base import AbstractSocketTransport
 from pysnmp.carrier import sockfix, sockmsg, error
 from pysnmp import debug
@@ -21,17 +23,21 @@ if hasattr(errno, 'EBADFD'):
     # bad FD may happen upon FD closure on n-1 select() event
     sockErrors[errno.EBADFD] = True
 
+
 class DgramSocketTransport(AbstractSocketTransport):
     sockType = socket.SOCK_DGRAM
     retryCount = 3
     retryInterval = 1
     addressType = lambda x: x
+
     def __init__(self, sock=None, sockMap=None):
         self.__outQueue = []
         self._sendto = lambda s, b, a: s.sendto(b, a)
+
         def __recvfrom(s, sz):
             d, a = s.recvfrom(sz)
             return d, self.addressType(a)
+
         self._recvfrom = __recvfrom
         AbstractSocketTransport.__init__(self, sock, sockMap)
 
@@ -40,10 +46,11 @@ class DgramSocketTransport(AbstractSocketTransport):
             try:
                 self.socket.bind(iface)
             except socket.error:
-                raise error.CarrierError('bind() for %s failed: %s' % (iface is None and "<all local>" or iface, sys.exc_info()[1]))
+                raise error.CarrierError(
+                    'bind() for %s failed: %s' % (iface is None and "<all local>" or iface, sys.exc_info()[1]))
         return self
 
-    def openServerMode(self, iface=None):
+    def openServerMode(self, iface):
         try:
             self.socket.bind(iface)
         except socket.error:
@@ -62,7 +69,7 @@ class DgramSocketTransport(AbstractSocketTransport):
 
     def enablePktInfo(self, flag=1):
         if not hasattr(self.socket, 'sendmsg') or \
-           not hasattr(self.socket, 'recvmsg'):
+                not hasattr(self.socket, 'recvmsg'):
             raise error.CarrierError('sendmsg()/recvmsg() interface is not supported by this OS and/or Python version')
 
         try:
@@ -100,7 +107,7 @@ class DgramSocketTransport(AbstractSocketTransport):
     def sendMessage(self, outgoingMessage, transportAddress):
         self.__outQueue.append(
             (outgoingMessage, self.normalizeAddress(transportAddress))
-            )
+        )
         debug.logger & debug.flagIO and debug.logger('sendMessage: outgoingMessage queued (%d octets) %s' % (len(outgoingMessage), debug.hexdump(outgoingMessage)))
 
     def normalizeAddress(self, transportAddress):
@@ -114,8 +121,8 @@ class DgramSocketTransport(AbstractSocketTransport):
         # one evil OS does not seem to support getsockname() for DGRAM sockets
         try:
             return self.socket.getsockname()
-        except:
-            return ('0.0.0.0', 0)
+        except Exception:
+            return '0.0.0.0', 0
 
     # asyncore API
     def handle_connect(self):
@@ -145,11 +152,10 @@ class DgramSocketTransport(AbstractSocketTransport):
 
     def handle_read(self):
         try:
-            incomingMessage, transportAddress = self._recvfrom(
-                self.socket, 65535
-            )
+            incomingMessage, transportAddress = self._recvfrom(self.socket, 65535)
             transportAddress = self.normalizeAddress(transportAddress)
-            debug.logger & debug.flagIO and debug.logger('handle_read: transportAddress %r -> %r incomingMessage (%d octets) %s' % (transportAddress, transportAddress.getLocalAddress(), len(incomingMessage), debug.hexdump(incomingMessage)))
+            debug.logger & debug.flagIO and debug.logger(
+                'handle_read: transportAddress %r -> %r incomingMessage (%d octets) %s' % (transportAddress, transportAddress.getLocalAddress(), len(incomingMessage), debug.hexdump(incomingMessage)))
             if not incomingMessage:
                 self.handle_close()
                 return
@@ -165,4 +171,4 @@ class DgramSocketTransport(AbstractSocketTransport):
                 raise error.CarrierError('recvfrom() failed: %s' % (sys.exc_info()[1],))
 
     def handle_close(self):
-        pass # no datagram connection
+        pass  # no datagram connection
diff --git a/pysnmp/carrier/asyncore/dgram/udp.py b/pysnmp/carrier/asyncore/dgram/udp.py
index f8b5ac1b..09b783dd 100644
--- a/pysnmp/carrier/asyncore/dgram/udp.py
+++ b/pysnmp/carrier/asyncore/dgram/udp.py
@@ -10,11 +10,14 @@ from pysnmp.carrier.asyncore.dgram.base import DgramSocketTransport
 
 domainName = snmpUDPDomain = (1, 3, 6, 1, 6, 1, 1)
 
+
 class UdpTransportAddress(tuple, AbstractTransportAddress):
     pass
 
+
 class UdpSocketTransport(DgramSocketTransport):
     sockFamily = AF_INET
     addressType = UdpTransportAddress
 
+
 UdpTransport = UdpSocketTransport
diff --git a/pysnmp/carrier/asyncore/dgram/udp6.py b/pysnmp/carrier/asyncore/dgram/udp6.py
index 947ecd23..c659dc35 100644
--- a/pysnmp/carrier/asyncore/dgram/udp6.py
+++ b/pysnmp/carrier/asyncore/dgram/udp6.py
@@ -11,9 +11,11 @@ import socket
 
 domainName = snmpUDP6Domain = (1, 3, 6, 1, 2, 1, 100, 1, 2)
 
+
 class Udp6TransportAddress(tuple, AbstractTransportAddress):
     pass
 
+
 class Udp6SocketTransport(DgramSocketTransport):
     sockFamily = socket.has_ipv6 and socket.AF_INET6 or None
     addressType = Udp6TransportAddress
@@ -22,7 +24,7 @@ class Udp6SocketTransport(DgramSocketTransport):
         if '%' in transportAddress[0]:  # strip zone ID
             ta = self.addressType((transportAddress[0].split('%')[0],
                                    transportAddress[1],
-                                   0,   # flowinfo
+                                   0,  # flowinfo
                                    0))  # scopeid
         else:
             ta = self.addressType((transportAddress[0],
@@ -34,4 +36,5 @@ class Udp6SocketTransport(DgramSocketTransport):
         else:
             return ta.setLocalAddress(self.getLocalAddress())
 
+
 Udp6Transport = Udp6SocketTransport
diff --git a/pysnmp/carrier/asyncore/dgram/unix.py b/pysnmp/carrier/asyncore/dgram/unix.py
index f8b193eb..7bac79af 100644
--- a/pysnmp/carrier/asyncore/dgram/unix.py
+++ b/pysnmp/carrier/asyncore/dgram/unix.py
@@ -6,6 +6,7 @@
 #
 import os
 import random
+
 try:
     from socket import AF_UNIX
 except ImportError:
@@ -17,12 +18,15 @@ domainName = snmpLocalDomain = (1, 3, 6, 1, 2, 1, 100, 1, 13)
 
 random.seed()
 
+
 class UnixTransportAddress(str, AbstractTransportAddress):
     pass
 
+
 class UnixSocketTransport(DgramSocketTransport):
     sockFamily = AF_UNIX
     addressType = UnixTransportAddress
+    _iface = ''
 
     def openClientMode(self, iface=None):
         if iface is None:
@@ -35,21 +39,22 @@ class UnixSocketTransport(DgramSocketTransport):
         if os.path.exists(iface):
             os.remove(iface)
         DgramSocketTransport.openClientMode(self, iface)
-        self.__iface = iface
+        self._iface = iface
         return self
 
     def openServerMode(self, iface):
         DgramSocketTransport.openServerMode(self, iface)
-        self.__iface = iface
+        self._iface = iface
         return self
 
     def closeTransport(self):
         DgramSocketTransport.closeTransport(self)
         try:
-            os.remove(self.__iface)
+            os.remove(self._iface)
         except OSError:
             pass
 
+
 UnixTransport = UnixSocketTransport
 
 # Compatibility stub
diff --git a/pysnmp/carrier/asyncore/dispatch.py b/pysnmp/carrier/asyncore/dispatch.py
index ae602549..78f6dcf8 100644
--- a/pysnmp/carrier/asyncore/dispatch.py
+++ b/pysnmp/carrier/asyncore/dispatch.py
@@ -12,9 +12,10 @@ from asyncore import loop
 from pysnmp.carrier.base import AbstractTransportDispatcher
 from pysnmp.error import PySnmpError
 
+
 class AsyncoreDispatcher(AbstractTransportDispatcher):
     def __init__(self):
-        self.__sockMap = {} # use own map for MT safety
+        self.__sockMap = {}  # use own map for MT safety
         self.timeout = 0.5
         AbstractTransportDispatcher.__init__(self)
 
diff --git a/pysnmp/carrier/base.py b/pysnmp/carrier/base.py
index 3aa2de4e..653ea3fe 100644
--- a/pysnmp/carrier/base.py
+++ b/pysnmp/carrier/base.py
@@ -6,6 +6,7 @@
 #
 from pysnmp.carrier import error
 
+
 class TimerCallable:
     def __init__(self, cbFun, callInterval):
         self.__cbFun = cbFun
@@ -35,6 +36,7 @@ class TimerCallable:
     def __ge__(self, cbFun):
         return self.__cbFun >= cbFun
 
+
 class AbstractTransportDispatcher:
     def __init__(self):
         self.__transports = {}
@@ -54,7 +56,7 @@ class AbstractTransportDispatcher:
         else:
             raise error.CarrierError(
                 'Unregistered transport %s' % (incomingTransport,)
-                )
+            )
 
         if self.__routingCbFun:
             recvId = self.__routingCbFun(
@@ -69,7 +71,7 @@ class AbstractTransportDispatcher:
             )
         else:
             raise error.CarrierError(
-                'No callback for "%r" found - loosing incoming event'%(recvId,)
+                'No callback for "%r" found - loosing incoming event' % (recvId,)
             )
 
     # Dispatcher API
@@ -111,7 +113,7 @@ class AbstractTransportDispatcher:
         if tDomain in self.__transports:
             raise error.CarrierError(
                 'Transport %s already registered' % (tDomain,)
-                )
+            )
         transport.registerCbFun(self._cbFun)
         self.__transports[tDomain] = transport
         self.__transportDomainMap[transport] = tDomain
@@ -120,7 +122,7 @@ class AbstractTransportDispatcher:
         if tDomain not in self.__transports:
             raise error.CarrierError(
                 'Transport %s not registered' % (tDomain,)
-                )
+            )
         self.__transports[tDomain].unregisterCbFun()
         del self.__transportDomainMap[self.__transports[tDomain]]
         del self.__transports[tDomain]
@@ -130,18 +132,18 @@ class AbstractTransportDispatcher:
             return self.__transports[transportDomain]
         raise error.CarrierError(
             'Transport %s not registered' % (transportDomain,)
-            )
+        )
 
     def sendMessage(self, outgoingMessage, transportDomain,
                     transportAddress):
         if transportDomain in self.__transports:
             self.__transports[transportDomain].sendMessage(
                 outgoingMessage, transportAddress
-                )
+            )
         else:
             raise error.CarrierError(
                 'No suitable transport domain for %s' % (transportDomain,)
-                )
+            )
 
     def getTimerResolution(self):
         return self.__timerResolution
@@ -156,7 +158,7 @@ class AbstractTransportDispatcher:
         return self.__ticks
 
     def handleTimerTick(self, timeNow):
-        if self.__nextTime == 0:   # initial initialization
+        if self.__nextTime == 0:  # initial initialization
             self.__nextTime = timeNow + self.__timerResolution - self.__timerDelta
 
         if self.__nextTime >= timeNow:
@@ -180,10 +182,7 @@ class AbstractTransportDispatcher:
             del self.__jobs[jobId]
 
     def jobsArePending(self):
-        if self.__jobs:
-            return 1
-        else:
-            return 0
+        return bool(self.__jobs)
 
     def runDispatcher(self, timeout=0.0):
         raise error.CarrierError('Method not implemented')
@@ -196,8 +195,10 @@ class AbstractTransportDispatcher:
         self.unregisterRecvCbFun()
         self.unregisterTimerCbFun()
 
+
 class AbstractTransportAddress:
     _localAddress = None
+
     def setLocalAddress(self, s):
         self._localAddress = s
         return self
@@ -208,10 +209,12 @@ class AbstractTransportAddress:
     def clone(self, localAddress=None):
         return self.__class__(self).setLocalAddress(localAddress is None and self.getLocalAddress() or localAddress)
 
+
 class AbstractTransport:
     protoTransportDispatcher = None
     addressType = AbstractTransportAddress
     _cbFun = None
+
     @classmethod
     def isCompatibleWithDispatcher(cls, transportDispatcher):
         return isinstance(transportDispatcher, cls.protoTransportDispatcher)
@@ -220,7 +223,7 @@ class AbstractTransport:
         if self._cbFun:
             raise error.CarrierError(
                 'Callback function %s already registered at %s' % (self._cbFun, self)
-                )
+            )
         self._cbFun = cbFun
 
     def unregisterCbFun(self):
@@ -234,7 +237,7 @@ class AbstractTransport:
     def openClientMode(self, iface=None):
         raise error.CarrierError('Method not implemented')
 
-    def openServerMode(self, iface=None):
+    def openServerMode(self, iface):
         raise error.CarrierError('Method not implemented')
 
     def sendMessage(self, outgoingMessage, transportAddress):
diff --git a/pysnmp/carrier/error.py b/pysnmp/carrier/error.py
index cdc3b308..290eb659 100644
--- a/pysnmp/carrier/error.py
+++ b/pysnmp/carrier/error.py
@@ -6,5 +6,6 @@
 #
 from pysnmp import error
 
+
 class CarrierError(error.PySnmpError):
     pass
diff --git a/pysnmp/carrier/sockfix.py b/pysnmp/carrier/sockfix.py
index 3abcd932..4c84321a 100644
--- a/pysnmp/carrier/sockfix.py
+++ b/pysnmp/carrier/sockfix.py
@@ -7,11 +7,11 @@
 import socket
 
 symbols = {
-    'IP_PKTINFO':       8,
-    'IP_TRANSPARENT':   19,
-    'SOL_IPV6':         41,
+    'IP_PKTINFO': 8,
+    'IP_TRANSPARENT': 19,
+    'SOL_IPV6': 41,
     'IPV6_RECVPKTINFO': 49,
-    'IPV6_PKTINFO':     50
+    'IPV6_PKTINFO': 50
 }
 
 for symbol in symbols:
diff --git a/pysnmp/carrier/twisted/base.py b/pysnmp/carrier/twisted/base.py
index 60f300ef..590717df 100644
--- a/pysnmp/carrier/twisted/base.py
+++ b/pysnmp/carrier/twisted/base.py
@@ -15,7 +15,10 @@
 from pysnmp.carrier.twisted.dispatch import TwistedDispatcher
 from pysnmp.carrier.base import AbstractTransport
 
+
 class AbstractTwistedTransport(AbstractTransport):
     protoTransportDispatcher = TwistedDispatcher
-    def __init__(self):
+
+    def __init__(self, sock=None, sockMap=None):
         self._writeQ = []
+        DgramTwistedTransport.__init__(self)
diff --git a/pysnmp/carrier/twisted/dgram/base.py b/pysnmp/carrier/twisted/dgram/base.py
index 4c556a4a..9dd2334b 100644
--- a/pysnmp/carrier/twisted/dgram/base.py
+++ b/pysnmp/carrier/twisted/dgram/base.py
@@ -11,6 +11,7 @@ from pysnmp.carrier.twisted.base import AbstractTwistedTransport
 from pysnmp.carrier import error
 from pysnmp import debug
 
+
 class DgramTwistedTransport(DatagramProtocol, AbstractTwistedTransport):
     """Base Twisted datagram Transport, to be used with TwistedDispatcher"""
 
diff --git a/pysnmp/carrier/twisted/dgram/udp.py b/pysnmp/carrier/twisted/dgram/udp.py
index 658359f6..3bf06413 100644
--- a/pysnmp/carrier/twisted/dgram/udp.py
+++ b/pysnmp/carrier/twisted/dgram/udp.py
@@ -12,11 +12,14 @@ from pysnmp.carrier import error
 
 domainName = snmpUDPDomain = (1, 3, 6, 1, 6, 1, 1)
 
+
 class UdpTransportAddress(tuple, AbstractTransportAddress):
     pass
 
+
 class UdpTwistedTransport(DgramTwistedTransport):
     addressType = UdpTransportAddress
+    _lport = None
 
     # AbstractTwistedTransport API
 
@@ -37,8 +40,11 @@ class UdpTwistedTransport(DgramTwistedTransport):
         return self
 
     def closeTransport(self):
-        d = self._lport.stopListening()
-        d and d.addCallback(lambda x: None)
-        DgramTwistedTransport.closeTransport(self)
+        if self._lport is not None:
+            d = self._lport.stopListening()
+            if d:
+                d.addCallback(lambda x: None)
+            DgramTwistedTransport.closeTransport(self)
+
 
 UdpTransport = UdpTwistedTransport
diff --git a/pysnmp/carrier/twisted/dgram/unix.py b/pysnmp/carrier/twisted/dgram/unix.py
index 5dc84bd3..61ccff93 100644
--- a/pysnmp/carrier/twisted/dgram/unix.py
+++ b/pysnmp/carrier/twisted/dgram/unix.py
@@ -17,6 +17,7 @@ class UnixTransportAddress(str, AbstractTransportAddress):
 
 class UnixTwistedTransport(DgramTwistedTransport):
     addressType = UnixTransportAddress
+    _lport = None
 
     # AbstractTwistedTransport API
 
@@ -27,7 +28,7 @@ class UnixTwistedTransport(DgramTwistedTransport):
             raise error.CarrierError(sys.exc_info()[1])
         return self
 
-    def openServerMode(self, iface=None):
+    def openServerMode(self, iface):
         try:
             self._lport = reactor.listenUNIXDatagram(iface, self)
         except Exception:
@@ -36,8 +37,10 @@ class UnixTwistedTransport(DgramTwistedTransport):
         return self
 
     def closeTransport(self):
-        d = self._lport.stopListening()
-        d and d.addCallback(lambda x: None)
+        if self._lport is not None:
+            d = self._lport.stopListening()
+            if d:
+                d.addCallback(lambda x: None)
         DgramTwistedTransport.closeTransport(self)
 
 UnixTransport = UnixTwistedTransport
diff --git a/pysnmp/carrier/twisted/dispatch.py b/pysnmp/carrier/twisted/dispatch.py
index 4cadec32..04cf9fae 100644
--- a/pysnmp/carrier/twisted/dispatch.py
+++ b/pysnmp/carrier/twisted/dispatch.py
@@ -17,8 +17,10 @@ from twisted.internet import reactor, task
 from pysnmp.carrier.base import AbstractTransportDispatcher
 from pysnmp.error import PySnmpError
 
+
 class TwistedDispatcher(AbstractTransportDispatcher):
     """TransportDispatcher based on twisted.internet.reactor"""
+
     def __init__(self, *args, **kwargs):
         AbstractTransportDispatcher.__init__(self)
         self.__transportCount = 0