diff --git a/ssh-audit.py b/ssh-audit.py
index c1dfaf2..9e11be0 100755
--- a/ssh-audit.py
+++ b/ssh-audit.py
@@ -28,21 +28,22 @@ import os, io, sys, socket, struct, random, errno, getopt, re, hashlib, base64
 
 VERSION = 'v1.6.1.dev'
 
-if sys.version_info >= (3,):
+if sys.version_info >= (3,):  # pragma: nocover
 	StringIO, BytesIO = io.StringIO, io.BytesIO
 	text_type = str
 	binary_type = bytes
-else:
+else:  # pragma: nocover
 	import StringIO as _StringIO  # pylint: disable=import-error
 	StringIO = BytesIO = _StringIO.StringIO
 	text_type = unicode  # pylint: disable=undefined-variable
 	binary_type = str
-try:
+try:  # pragma: nocover
 	# pylint: disable=unused-import
-	from typing import List, Tuple, Optional, Callable, Union, Any
+	from typing import List, Set, Sequence, Tuple, Iterable
+	from typing import Callable, Optional, Union, Any
 except ImportError:  # pragma: nocover
 	pass
-try:
+try:  # pragma: nocover
 	from colorama import init as colorama_init
 	colorama_init()  # pragma: nocover
 except ImportError:  # pragma: nocover
@@ -53,13 +54,16 @@ def usage(err=None):
 	# type: (Optional[str]) -> None
 	uout = Output()
 	p = os.path.basename(sys.argv[0])
-	uout.head('# {0} {1}, moo@arthepsy.eu'.format(p, VERSION))
+	uout.head('# {0} {1}, moo@arthepsy.eu\n'.format(p, VERSION))
 	if err is not None:
 		uout.fail('\n' + err)
-	uout.info('\nusage: {0} [-12bnv] [-l <level>] <host[:port]>\n'.format(p))
+	uout.info('usage: {0} [-1246pbnvl] <host>\n'.format(p))
 	uout.info('   -h,  --help             print this help')
 	uout.info('   -1,  --ssh1             force ssh version 1 only')
 	uout.info('   -2,  --ssh2             force ssh version 2 only')
+	uout.info('   -4,  --ipv4             enable IPv4 (order of precedence)')
+	uout.info('   -6,  --ipv6             enable IPv6 (order of precedence)')
+	uout.info('   -p,  --port=<port>      port to connect')
 	uout.info('   -b,  --batch            batch output')
 	uout.info('   -n,  --no-colors        disable colors')
 	uout.info('   -v,  --verbose          verbose output')
@@ -69,6 +73,7 @@ def usage(err=None):
 
 
 class AuditConf(object):
+	# pylint: disable=too-many-instance-attributes
 	def __init__(self, host=None, port=22):
 		# type: (Optional[str], int) -> None
 		self.host = host
@@ -79,12 +84,35 @@ class AuditConf(object):
 		self.colors = True
 		self.verbose = False
 		self.minlevel = 'info'
+		self.ipvo = ()  # type: Sequence[int]
+		self.ipv4 = False
+		self.ipv6 = False
 	
 	def __setattr__(self, name, value):
-		# type: (str, Union[str, int, bool]) -> None
+		# type: (str, Union[str, int, bool, Sequence[int]]) -> None
 		valid = False
 		if name in ['ssh1', 'ssh2', 'batch', 'colors', 'verbose']:
 			valid, value = True, True if value else False
+		elif name in ['ipv4', 'ipv6']:
+			valid = False
+			value = True if value else False
+			ipv = 4 if name == 'ipv4' else 6
+			if value:
+				value = tuple(list(self.ipvo) + [ipv])
+			else:
+				if len(self.ipvo) == 0:
+					value = (6,) if ipv == 4 else (4,)
+				else:
+					value = tuple(filter(lambda x: x != ipv, self.ipvo))
+			self.__setattr__('ipvo', value)
+		elif name == 'ipvo':
+			if isinstance(value, (tuple, list)):
+				uniq_value = utils.unique_seq(value)
+				value = tuple(filter(lambda x: x in (4, 6), uniq_value))
+				valid = True
+				ipv_both = len(value) == 0
+				object.__setattr__(self, 'ipv4', ipv_both or 4 in value)
+				object.__setattr__(self, 'ipv6', ipv_both or 6 in value)
 		elif name == 'port':
 			valid, port = True, utils.parse_int(value)
 			if port < 1 or port > 65535:
@@ -105,13 +133,14 @@ class AuditConf(object):
 		# pylint: disable=too-many-branches
 		aconf = cls()
 		try:
-			sopts = 'h12bnvl:'
-			lopts = ['help', 'ssh1', 'ssh2', 'batch',
-			         'no-colors', 'verbose', 'level=']
+			sopts = 'h1246p:bnvl:'
+			lopts = ['help', 'ssh1', 'ssh2', 'ipv4', 'ipv6', 'port',
+			         'batch', 'no-colors', 'verbose', 'level=']
 			opts, args = getopt.getopt(args, sopts, lopts)
 		except getopt.GetoptError as err:
 			usage_cb(str(err))
 		aconf.ssh1, aconf.ssh2 = False, False
+		oport = None
 		for o, a in opts:
 			if o in ('-h', '--help'):
 				usage_cb()
@@ -119,6 +148,12 @@ class AuditConf(object):
 				aconf.ssh1 = True
 			elif o in ('-2', '--ssh2'):
 				aconf.ssh2 = True
+			elif o in ('-4', '--ipv4'):
+				aconf.ipv4 = True
+			elif o in ('-6', '--ipv6'):
+				aconf.ipv6 = True
+			elif o in ('-p', '--port'):
+				oport = a
 			elif o in ('-b', '--batch'):
 				aconf.batch = True
 				aconf.verbose = True
@@ -132,14 +167,20 @@ class AuditConf(object):
 				aconf.minlevel = a
 		if len(args) == 0:
 			usage_cb()
-		s = args[0].split(':')
-		host, port = s[0].strip(), 22
-		if len(s) > 1:
-			port = utils.parse_int(s[1])
+		if oport is not None:
+			host = args[0]
+			port = utils.parse_int(oport)
+		else:
+			s = args[0].split(':')
+			host = s[0].strip()
+			if len(s) == 2:
+				oport, port = s[1], utils.parse_int(s[1])
+			else:
+				oport, port = '22', 22
 		if not host:
 			usage_cb('host is empty')
 		if port <= 0 or port > 65535:
-			usage_cb('port {0} is not valid'.format(s[1]))
+			usage_cb('port {0} is not valid'.format(oport))
 		aconf.host = host
 		aconf.port = port
 		if not (aconf.ssh1 or aconf.ssh2):
@@ -1038,24 +1079,67 @@ class SSH(object):  # pylint: disable=too-few-public-methods
 		
 		SM_BANNER_SENT = 1
 		
-		def __init__(self, host, port, cto=3.0, rto=5.0):
-			# type: (str, int, float, float) -> None
+		def __init__(self, host, port):
+			# type: (str, int) -> None
+			super(SSH.Socket, self).__init__()
 			self.__block_size = 8
 			self.__state = 0
 			self.__header = []  # type: List[text_type]
 			self.__banner = None  # type: Optional[SSH.Banner]
-			super(SSH.Socket, self).__init__()
-			try:
-				self.__sock = socket.create_connection((host, port), cto)
-				self.__sock.settimeout(rto)
-			except Exception as e:  # pylint: disable=broad-except
-				out.fail('[fail] {0}'.format(e))
-				sys.exit(1)
+			self.__host = host
+			self.__port = port
+			self.__sock = None  # type: socket.socket
 		
 		def __enter__(self):
 			# type: () -> SSH.Socket
 			return self
 		
+		def _resolve(self, ipvo):
+			# type: (Sequence[int]) -> Iterable[Tuple[int, Tuple[Any, ...]]]
+			ipvo = tuple(filter(lambda x: x in (4, 6), utils.unique_seq(ipvo)))
+			ipvo_len = len(ipvo)
+			prefer_ipvo = ipvo_len > 0
+			prefer_ipv4 = prefer_ipvo and ipvo[0] == 4
+			if len(ipvo) == 1:
+				family = {4: socket.AF_INET, 6: socket.AF_INET6}.get(ipvo[0])
+			else:
+				family = socket.AF_UNSPEC
+			try:
+				stype = socket.SOCK_STREAM
+				r = socket.getaddrinfo(self.__host, self.__port, family, stype)
+				if prefer_ipvo:
+					r = sorted(r, key=lambda x: x[0], reverse=not prefer_ipv4)
+				check = any(stype == rline[2] for rline in r)
+				for (af, socktype, proto, canonname, addr) in r:
+					if not check or socktype == socket.SOCK_STREAM:
+						yield (af, addr)
+			except socket.error as e:
+				out.fail('[exception] {0}'.format(e))
+				sys.exit(1)
+		
+		def connect(self, ipvo=(), cto=3.0, rto=5.0):
+			# type: (Sequence[int], float, float) -> None
+			err = None
+			for (af, addr) in self._resolve(ipvo):
+				s = None
+				try:
+					s = socket.socket(af, socket.SOCK_STREAM)
+					s.settimeout(cto)
+					s.connect(addr)
+					s.settimeout(rto)
+					self.__sock = s
+					return
+				except socket.error as e:
+					err = e
+					self._close_socket(s)
+			if err is None:
+				errm = 'host {0} has no DNS records'.format(self.__host)
+			else:
+				errt = (self.__host, self.__port, err)
+				errm = 'cannot connect to {0} port {1}: {2}'.format(*errt)
+			out.fail('[exception] {0}'.format(errm))
+			sys.exit(1)
+		
 		def get_banner(self, sshv=2):
 			# type: (int) -> Tuple[Optional[SSH.Banner], List[text_type]]
 			banner = 'SSH-{0}-OpenSSH_7.3'.format('1.5' if sshv == 1 else '2.0')
@@ -1188,6 +1272,15 @@ class SSH(object):  # pylint: disable=too-few-public-methods
 			data = struct.pack('>Ib', plen, padding) + payload + pad_bytes
 			return self.send(data)
 		
+		def _close_socket(self, s):
+			# type: (Optional[socket.socket]) -> None
+			try:
+				if s is not None:
+					s.shutdown(socket.SHUT_RDWR)
+					s.close()
+			except:  # pylint: disable=bare-except
+				pass
+		
 		def __del__(self):
 			# type: () -> None
 			self.__cleanup()
@@ -1198,11 +1291,7 @@ class SSH(object):  # pylint: disable=too-few-public-methods
 		
 		def __cleanup(self):
 			# type: () -> None
-			try:
-				self.__sock.shutdown(socket.SHUT_RDWR)
-				self.__sock.close()
-			except:  # pylint: disable=bare-except
-				pass
+			self._close_socket(self.__sock)
 
 
 class KexDH(object):
@@ -1847,6 +1936,21 @@ class Utils(object):
 			return cls.to_ntext(v.encode('ascii', errors))
 		raise cls._type_err(v, 'ascii')
 	
+	@classmethod
+	def unique_seq(cls, seq):
+		# type: (Sequence[Any]) -> Sequence[Any]
+		seen = set()  # type: Set[Any]
+		
+		def _seen_add(x):
+			# type: (Any) -> bool
+			seen.add(x)
+			return False
+		
+		if isinstance(seq, tuple):
+			return tuple(x for x in seq if x not in seen and not _seen_add(x))
+		else:
+			return [x for x in seq if x not in seen and not _seen_add(x)]
+		
 	@staticmethod
 	def parse_int(v):
 		# type: (Any) -> int
@@ -1863,6 +1967,7 @@ def audit(aconf, sshv=None):
 	out.verbose = aconf.verbose
 	out.minlevel = aconf.minlevel
 	s = SSH.Socket(aconf.host, aconf.port)
+	s.connect(aconf.ipvo)
 	if sshv is None:
 		sshv = 2 if aconf.ssh2 else 1
 	err = None
diff --git a/test/conftest.py b/test/conftest.py
index 28ab4ef..524c0fa 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -1,10 +1,14 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
-import pytest, os, sys, io, socket
+import os
+import io
+import sys
+import socket
+import pytest
 
 
 if sys.version_info[0] == 2:
-	import StringIO
+	import StringIO  # pylint: disable=import-error
 	StringIO = StringIO.StringIO
 else:
 	StringIO = io.StringIO
@@ -17,6 +21,7 @@ def ssh_audit():
 	return __import__('ssh-audit')
 
 
+# pylint: disable=attribute-defined-outside-init
 class _OutputSpy(list):
 	def begin(self):
 		self.__out = StringIO()
@@ -50,11 +55,14 @@ class _VirtualSocket(object):
 		if method_error:
 			raise method_error
 	
-	def _connect(self, address):
+	def connect(self, address):
+		return self._connect(address, False)
+	
+	def _connect(self, address, ret=True):
 		self.peer_address = address
 		self._connected = True
 		self._check_err('connect')
-		return self
+		return self if ret else None
 	
 	def settimeout(self, timeout):
 		self.timeout = timeout
@@ -77,6 +85,7 @@ class _VirtualSocket(object):
 		pass
 	
 	def accept(self):
+		# pylint: disable=protected-access
 		conn = _VirtualSocket()
 		conn.sock_address = self.sock_address
 		conn.peer_address = ('127.0.0.1', 0)
@@ -84,6 +93,7 @@ class _VirtualSocket(object):
 		return conn, conn.peer_address
 	
 	def recv(self, bufsize, flags=0):
+		# pylint: disable=unused-argument
 		if not self._connected:
 			raise socket.error(54, 'Connection reset by peer')
 		if not len(self.rdata) > 0:
@@ -103,10 +113,18 @@ class _VirtualSocket(object):
 @pytest.fixture()
 def virtual_socket(monkeypatch):
 	vsocket = _VirtualSocket()
-	def _c(address):
-		return vsocket._connect(address)
+	
+	# pylint: disable=unused-argument
+	def _socket(family=socket.AF_INET,
+	            socktype=socket.SOCK_STREAM,
+	            proto=0,
+	            fileno=None):
+		return vsocket
+	
 	def _cc(address, timeout=0, source_address=None):
-		return vsocket._connect(address)
+		# pylint: disable=protected-access
+		return vsocket._connect(address, True)
+	
 	monkeypatch.setattr(socket, 'create_connection', _cc)
-	monkeypatch.setattr(socket.socket, 'connect', _c)
+	monkeypatch.setattr(socket, 'socket', _socket)
 	return vsocket
diff --git a/test/test_auditconf.py b/test/test_auditconf.py
index 6c23c2a..3472c42 100644
--- a/test/test_auditconf.py
+++ b/test/test_auditconf.py
@@ -20,7 +20,10 @@ class TestAuditConf(object):
 			'batch': False,
 			'colors': True,
 			'verbose': False,
-			'minlevel': 'info'
+			'minlevel': 'info',
+			'ipv4': True,
+			'ipv6': True,
+			'ipvo': ()
 		}
 		for k, v in kwargs.items():
 			options[k] = v
@@ -32,6 +35,9 @@ class TestAuditConf(object):
 		assert conf.colors is options['colors']
 		assert conf.verbose is options['verbose']
 		assert conf.minlevel == options['minlevel']
+		assert conf.ipv4 == options['ipv4']
+		assert conf.ipv6 == options['ipv6']
+		assert conf.ipvo == options['ipvo']
 	
 	def test_audit_conf_defaults(self):
 		conf = self.AuditConf()
@@ -57,6 +63,58 @@ class TestAuditConf(object):
 				conf.port = port
 			excinfo.match(r'.*invalid port.*')
 	
+	def test_audit_conf_ipvo(self):
+		# ipv4-only
+		conf = self.AuditConf()
+		conf.ipv4 = True
+		assert conf.ipv4 is True
+		assert conf.ipv6 is False
+		assert conf.ipvo == (4,)
+		# ipv6-only
+		conf = self.AuditConf()
+		conf.ipv6 = True
+		assert conf.ipv4 is False
+		assert conf.ipv6 is True
+		assert conf.ipvo == (6,)
+		# ipv4-only (by removing ipv6)
+		conf = self.AuditConf()
+		conf.ipv6 = False
+		assert conf.ipv4 is True
+		assert conf.ipv6 is False
+		assert conf.ipvo == (4, )
+		# ipv6-only (by removing ipv4)
+		conf = self.AuditConf()
+		conf.ipv4 = False
+		assert conf.ipv4 is False
+		assert conf.ipv6 is True
+		assert conf.ipvo == (6, )
+		# ipv4-preferred
+		conf = self.AuditConf()
+		conf.ipv4 = True
+		conf.ipv6 = True
+		assert conf.ipv4 is True
+		assert conf.ipv6 is True
+		assert conf.ipvo == (4, 6)
+		# ipv6-preferred
+		conf = self.AuditConf()
+		conf.ipv6 = True
+		conf.ipv4 = True
+		assert conf.ipv4 is True
+		assert conf.ipv6 is True
+		assert conf.ipvo == (6, 4)
+		# ipvo empty
+		conf = self.AuditConf()
+		conf.ipvo = ()
+		assert conf.ipv4 is True
+		assert conf.ipv6 is True
+		assert conf.ipvo == ()
+		# ipvo validation
+		conf = self.AuditConf()
+		conf.ipvo = (1, 2, 3, 4, 5, 6)
+		assert conf.ipvo == (4, 6)
+		conf.ipvo = (4, 4, 4, 6, 6)
+		assert conf.ipvo == (4, 6)
+	
 	def test_audit_conf_minlevel(self):
 		conf = self.AuditConf()
 		for level in ['info', 'warn', 'fail']:
@@ -68,6 +126,7 @@ class TestAuditConf(object):
 			excinfo.match(r'.*invalid level.*')
 	
 	def test_audit_conf_cmdline(self):
+		# pylint: disable=too-many-statements
 		c = lambda x: self.AuditConf.from_cmdline(x.split(), self.usage)  # noqa
 		with pytest.raises(SystemExit):
 			conf = c('')
@@ -87,20 +146,36 @@ class TestAuditConf(object):
 		self._test_conf(conf, host='github.com')
 		conf = c('localhost:2222')
 		self._test_conf(conf, host='localhost', port=2222)
+		conf = c('-p 2222 localhost')
+		self._test_conf(conf, host='localhost', port=2222)
 		with pytest.raises(SystemExit):
 			conf = c('localhost:')
 		with pytest.raises(SystemExit):
 			conf = c('localhost:abc')
+		with pytest.raises(SystemExit):
+			conf = c('-p abc localhost')
 		with pytest.raises(SystemExit):
 			conf = c('localhost:-22')
+		with pytest.raises(SystemExit):
+			conf = c('-p -22 localhost')
 		with pytest.raises(SystemExit):
 			conf = c('localhost:99999')
+		with pytest.raises(SystemExit):
+			conf = c('-p 99999 localhost')
 		conf = c('-1 localhost')
 		self._test_conf(conf, host='localhost', ssh1=True, ssh2=False)
 		conf = c('-2 localhost')
 		self._test_conf(conf, host='localhost', ssh1=False, ssh2=True)
 		conf = c('-12 localhost')
 		self._test_conf(conf, host='localhost', ssh1=True, ssh2=True)
+		conf = c('-4 localhost')
+		self._test_conf(conf, host='localhost', ipv4=True, ipv6=False, ipvo=(4,))
+		conf = c('-6 localhost')
+		self._test_conf(conf, host='localhost', ipv4=False, ipv6=True, ipvo=(6,))
+		conf = c('-46 localhost')
+		self._test_conf(conf, host='localhost', ipv4=True, ipv6=True, ipvo=(4, 6))
+		conf = c('-64 localhost')
+		self._test_conf(conf, host='localhost', ipv4=True, ipv6=True, ipvo=(6, 4))
 		conf = c('-b localhost')
 		self._test_conf(conf, host='localhost', batch=True, verbose=True)
 		conf = c('-n localhost')