diff --git a/chewie/chewie.py b/chewie/chewie.py
index a046688..cfbb661 100644
--- a/chewie/chewie.py
+++ b/chewie/chewie.py
@@ -99,19 +99,19 @@ class Chewie:
 
     def auth_failure(self, src_mac, port_id):
         """failure shim between faucet and chewie
-                Args:
-                    src_mac (MacAddress): the mac of the failed supplicant
-                    port_id (MacAddress): the 'mac' identifier of what switch port
-                     the failure is on"""
+        Args:
+            src_mac (MacAddress): the mac of the failed supplicant
+            port_id (MacAddress): the 'mac' identifier of what switch port
+             the failure is on"""
         if self.failure_handler:
             self.failure_handler(src_mac, port_id)
 
     def auth_logoff(self, src_mac, port_id):
         """logoff shim between faucet and chewie
-                Args:
-                    src_mac (MacAddress): the mac of the logoff supplicant
-                    port_id (MacAddress): the 'mac' identifier of what switch port
-                     the logoff is on"""
+        Args:
+            src_mac (MacAddress): the mac of the logoff supplicant
+            port_id (MacAddress): the 'mac' identifier of what switch port
+             the logoff is on"""
         if self.logoff_handler:
             self.logoff_handler(src_mac, port_id)
 
@@ -144,7 +144,7 @@ class Chewie:
                 message, dst_mac = MessageParser.ethernet_parse(packed_message)
                 self.logger.info("eap EAP(): %s", message)
                 self.logger.info("Received message: %s" % message.__dict__)
-                sm = self.get_state_machine(message.src_mac)
+                sm = self.get_state_machine(message.src_mac, dst_mac)
                 event = EventMessageReceived(message, dst_mac)
                 sm.event(event)
         except Exception as e:
@@ -160,7 +160,7 @@ class Chewie:
         try:
             while True:
                 sleep(0)
-                eap_message, src_mac, username, state = self.radius_output_messages.get()
+                eap_message, src_mac, username, state, port_id = self.radius_output_messages.get()
                 self.logger.info("got eap to send to radius.. mac: %s %s, username: %s",
                                  type(src_mac), src_mac, username)
                 state_dict = None
@@ -169,7 +169,7 @@ class Chewie:
                 self.logger.info("Sending to RADIUS eap message %s with state %s",
                                  eap_message.__dict__, state_dict)
                 radius_packet_id = self.get_next_radius_packet_id()
-                self.packet_id_to_mac[radius_packet_id] = src_mac
+                self.packet_id_to_mac[radius_packet_id] = {'src_mac': src_mac, 'port_id': port_id}
                 # message is eap. needs to be wrapped into a radius packet.
                 request_authenticator = os.urandom(16)
                 self.packet_id_to_request_authenticator[radius_packet_id] = request_authenticator
@@ -258,17 +258,21 @@ class Chewie:
         Returns:
             FullEAPStateMachine
         """
-        return self.get_state_machine(self.packet_id_to_mac[packet_id])
+        return self.get_state_machine(**self.packet_id_to_mac[packet_id])
 
-    def get_state_machine(self, src_mac):
+    def get_state_machine(self, src_mac, port_id):
         """Gets or creates if it does not already exist an FullEAPStateMachine for the src_mac.
         Args:
-            src_mac (MACAddress): who's to get.
+            src_mac (MacAddress): who's to get.
+            port_id (MacAddress): ID of the port where the src_mac is.
 
         Returns:
             FullEAPStateMachine
         """
-        sm = self.state_machines.get(src_mac, None)
+        port_sms = self.state_machines.get(str(port_id), None)
+        if port_sms is None:
+            self.state_machines[str(port_id)] = {}
+        sm = self.state_machines[str(port_id)].get(src_mac, None)
         if not sm:
             sm = FullEAPStateMachine(self.eap_output_messages, self.radius_output_messages, src_mac,
                                      self.timer_scheduler, self.auth_success,
@@ -276,7 +280,7 @@ class Chewie:
             sm.eapRestart = True
             # TODO what if port is not actually enabled, but then how did they auth?
             sm.portEnabled = True
-            self.state_machines[src_mac] = sm
+            self.state_machines[str(port_id)][src_mac] = sm
         return sm
 
     def get_next_radius_packet_id(self):
diff --git a/chewie/eap_state_machine.py b/chewie/eap_state_machine.py
index aba5f5a..ac60dab 100644
--- a/chewie/eap_state_machine.py
+++ b/chewie/eap_state_machine.py
@@ -712,7 +712,8 @@ class FullEAPStateMachine:
             if self.aaaEapRespData.code == Eap.RESPONSE:
                 self.radius_output_messages.put((self.aaaEapRespData, self.src_mac,
                                                  self.aaaIdentity.identity,
-                                                 self.radius_state_attribute))
+                                                 self.radius_state_attribute,
+                                                 self.port_id_mac))
                 self.sent_count += 1
                 self.set_timer()
             self.aaaEapResp = False

diff --git a/test/test_chewie.py b/test/test_chewie.py
new file mode 100644
index 0000000..931cdda
--- /dev/null
+++ b/test/test_chewie.py
@@ -0,0 +1,76 @@
+"""Unittests for chewie/chewie.py"""
+
+import logging
+import unittest
+
+from chewie.chewie import Chewie
+
+
+def auth_handler(chewie, client_mac, port_id_mac):  # pylint: disable=unused-argument
+    """dummy handler for successful authentications"""
+    print('Successful auth from MAC %s on port: %s' % (str(client_mac), str(port_id_mac)))
+
+
+def failure_handler(chewie, client_mac, port_id_mac):  # pylint: disable=unused-argument
+    """dummy handler for failed authentications"""
+    print('failure from MAC %s on port: %s' % (str(client_mac), str(port_id_mac)))
+
+
+def logoff_handler(chewie, client_mac, port_id_mac):  # pylint: disable=unused-argument
+    """dummy handler for logoffs"""
+    print('logoff from MAC %s on port: %s' % (str(client_mac), str(port_id_mac)))
+
+
+class ChewieTestCase(unittest.TestCase):
+    """Main chewie.py test class"""
+
+    def setUp(self):
+        logger = logging.getLogger()
+
+        self.chewie = Chewie('lo', logger,
+                             auth_handler, failure_handler, logoff_handler,
+                             '127.0.0.1', 1812, 'SECRET',
+                             '44:44:44:44:44:44')
+
+    def test_get_sm(self):
+        """Tests Chewie.get_state_machine()"""
+        self.assertEqual(len(self.chewie.state_machines), 0)
+        # creates the sm if it doesn't exist
+        sm = self.chewie.get_state_machine('12:34:56:78:9a:bc',  # pylint: disable=invalid-name
+                                           '00:00:00:00:00:01')
+
+        self.assertEqual(len(self.chewie.state_machines), 1)
+
+        self.assertIs(sm, self.chewie.get_state_machine('12:34:56:78:9a:bc',
+                                                        '00:00:00:00:00:01'))
+
+        self.assertIsNot(sm, self.chewie.get_state_machine('12:34:56:78:9a:bc',
+                                                           '00:00:00:00:00:02'))
+        self.assertIsNot(sm, self.chewie.get_state_machine('ab:cd:ef:12:34:56',
+                                                           '00:00:00:00:00:01'))
+
+        # 2 ports
+        self.assertEqual(len(self.chewie.state_machines), 2)
+        # port 1 has 2 macs
+        self.assertEqual(len(self.chewie.state_machines['00:00:00:00:00:01']), 2)
+        # port 2 has 1 mac
+        self.assertEqual(len(self.chewie.state_machines['00:00:00:00:00:02']), 1)
+
+    def test_get_sm_by_packet_id(self):
+        """Tests Chewie.get_sm_by_packet_id()"""
+        self.chewie.packet_id_to_mac[56] = {'src_mac': '12:34:56:78:9a:bc',
+                                            'port_id': '00:00:00:00:00:01'}
+        sm = self.chewie.get_state_machine('12:34:56:78:9a:bc',  # pylint: disable=invalid-name
+                                           '00:00:00:00:00:01')
+
+        self.assertIs(self.chewie.get_state_machine_from_radius_packet_id(56),
+                      sm)
+        with self.assertRaises(KeyError):
+            self.chewie.get_state_machine_from_radius_packet_id(20)
+
+    def test_get_next_radius_packet_id(self):
+        """Tests Chewie.get_next_radius_packet_id()"""
+        for i in range(0, 260):
+            _i = i % 256
+            self.assertEqual(self.chewie.get_next_radius_packet_id(),
+                             _i)
diff --git a/test/test_full_state_machine.py b/test/test_full_state_machine.py
index 713b8ae..18a6b23 100644
--- a/test/test_full_state_machine.py
+++ b/test/test_full_state_machine.py
@@ -161,9 +161,11 @@ class FullStateMachineStartTestCase(unittest.TestCase):
         self.assertEqual(self.sm.currentState, self.sm.IDLE2)
 
         self.assertEqual(self.eap_output_queue.qsize(), 1)
-        self.assertIsInstance(self.eap_output_queue.get_nowait()[0], Md5ChallengeMessage)
+        output = self.eap_output_queue.get_nowait()[0]
+        self.assertIsInstance(output, Md5ChallengeMessage)
 
         self.assertEqual(self.radius_output_queue.qsize(), 0)
+        return output
 
     def test_md5_challenge_response(self):
         self.test_md5_challenge_request()
@@ -224,9 +226,9 @@ class FullStateMachineStartTestCase(unittest.TestCase):
         self.assertEqual(self.radius_output_queue.qsize(), 0)
 
     def test_discard2(self):
-        self.test_md5_challenge_request()
+        request = self.test_md5_challenge_request()
 
-        message = Md5ChallengeMessage(self.src_mac, 222, Eap.RESPONSE,
+        message = Md5ChallengeMessage(self.src_mac, request.message_id + 10, Eap.RESPONSE,
                                       build_byte_string("3a535f0ee8c6b34fe714aa7dad9a0e15"),
                                       b"host1user")
         self.sm.event(EventMessageReceived(message, None))
@@ -235,9 +237,9 @@ class FullStateMachineStartTestCase(unittest.TestCase):
         self.assertEqual(self.radius_output_queue.qsize(), 0)
 
     def test_discard(self):
-        self.test_eap_start()
-
-        message = IdentityMessage(self.src_mac, 40, Eap.RESPONSE, "host1user")
+        message = self.test_eap_start()
+        # Make a message that will be discarded (id here is not sequential)
+        message = IdentityMessage(self.src_mac, message.message_id + 10, Eap.RESPONSE, "host1user")
         self.sm.event(EventMessageReceived(message, None))
         self.assertEqual(self.sm.currentState, self.sm.IDLE)
 

Could verify that all EAP packets in a sequence come from the same port.
If we have 2 hosts with same MAC (e.g. 1 good, 1 Malicious) and they try to authenticate, it could be possible to authenticate on the malicious port when good is successful if malicious sends eap packet before the radius access-accept has been received, and thus setting the sm.port_id_mac.

Basically we want to stop this. 2 obvious ways.
1. Make a state machine tied to a mac and port. So in the above case there would be 2 state machines.
2. some sort of verification logic.

Option 1 looks easier to implement.
Will also handle if 2 good, both would auth.

test/test_chewie.py::ChewieTestCase::test_get_sm test/test_chewie.py::ChewieTestCase::test_get_sm_by_packet_id
test/test_chewie.py::ChewieTestCase::test_get_next_radius_packet_id test/test_full_state_machine.py::FullStateMachineStartTestCase::test_disabled_state test/test_full_state_machine.py::FullStateMachineStartTestCase::test_discard test/test_full_state_machine.py::FullStateMachineStartTestCase::test_discard2 test/test_full_state_machine.py::FullStateMachineStartTestCase::test_eap_restart test/test_full_state_machine.py::FullStateMachineStartTestCase::test_eap_start test/test_full_state_machine.py::FullStateMachineStartTestCase::test_failure2 test/test_full_state_machine.py::FullStateMachineStartTestCase::test_identity_response test/test_full_state_machine.py::FullStateMachineStartTestCase::test_logoff2 test/test_full_state_machine.py::FullStateMachineStartTestCase::test_logoff_from_idle2 test/test_full_state_machine.py::FullStateMachineStartTestCase::test_md5_challenge_request test/test_full_state_machine.py::FullStateMachineStartTestCase::test_md5_challenge_response test/test_full_state_machine.py::FullStateMachineStartTestCase::test_success2 test/test_full_state_machine.py::FullStateMachineStartTestCase::test_timeout_failure2_from_aaa_timeout test/test_full_state_machine.py::FullStateMachineStartTestCase::test_timeout_failure2_from_max_retransmits test/test_full_state_machine.py::FullStateMachineStartTestCase::test_timeout_failure_from_max_retransmits test/test_full_state_machine.py::FullStateMachineStartTestCase::test_ttls_request