diff --git a/txssmi/builder.py b/txssmi/builder.py
index cd2e504..e0e7fc9 100644
--- a/txssmi/builder.py
+++ b/txssmi/builder.py
@@ -42,16 +42,13 @@ def __init__(self, **kwargs):
     def __iter__(self):
         parts = [SSMI_HEADER, self.command_id]
         parts.extend([self.values.get(fn) for fn in self.fields])
-        return iter(map(unicode, parts))
-
-    def __unicode__(self):
-        return u','.join(self)
+        return iter(parts)
 
     def __str__(self):
-        return unicode(self).encode('utf-8')
+        return ','.join(self)
 
     def __eq__(self, other):
-        return unicode(other) == unicode(self)
+        return str(other) == str(self)
 
     def __getattr__(self, attr):
         if attr in self.fields:
diff --git a/txssmi/commands.py b/txssmi/commands.py
index 929ea5e..059d233 100644
--- a/txssmi/commands.py
+++ b/txssmi/commands.py
@@ -5,9 +5,9 @@
 
 
 Login = SSMIRequest.create('LOGIN')
-SendSMS = SSMIRequest.create('SEND_SMS', {'validity': 0})
+SendSMS = SSMIRequest.create('SEND_SMS', {'validity': '0'})
 SendBinarySMS = SSMIRequest.create('SEND_BINARY_SMS', {
-    'validity': 0,
+    'validity': '0',
     'coding': CODING_7BIT,
     'pid': PROTOCOL_STANDARD,
 })
diff --git a/txssmi/protocol.py b/txssmi/protocol.py
index f9c4298..0e14c32 100644
--- a/txssmi/protocol.py
+++ b/txssmi/protocol.py
@@ -1,4 +1,5 @@
 # -*- test-case-name: txssmi.tests.test_protocol -*-
+# -*- coding: utf-8 -*-
 
 import random
 from collections import defaultdict
@@ -25,7 +26,7 @@
 
 class SSMIProtocol(LineReceiver):
 
-    delimeter = '\r'
+    delimiter = b'\r'
     noisy = False
     clock = reactor
 
@@ -36,17 +37,22 @@ def __init__(self):
         self.imsi_lookup_reply_map = defaultdict(lambda: DeferredQueue())
         self.link_check = LoopingCall(self.send_link_request)
         self.link_check.clock = self.clock
-        self.imsi_lookups = {}
+
+    def connectionMade(self):
+        log.msg('Connection made.')
+
+    def connectionLost(self, reason):
+        log.msg('Connection lost: %s' % (reason,))
 
     def emit(self, prefix, msg):
         if self.noisy:
-            log.msg('%s %s' % (prefix, msg))
+            log.msg('%s %r' % (prefix, msg))
 
     def lineReceived(self, line):
         command = SSMIResponse.parse(line)
-        self.emit('<<', str(command))
+        self.emit('<<', command)
         handler = getattr(self, 'handle_%s' % (command.command_name,))
-        return maybeDeferred(handler, command)
+        maybeDeferred(handler, command)
 
     def send_command(self, command):
         self.emit('>>', str(command))
@@ -80,13 +86,13 @@ def cb(cmd):
         d.addCallback(cb)
         return d
 
-    def send_message(self, msisdn, message, validity=0):
+    def send_message(self, msisdn, message, validity='0'):
         d = self.send_command(
             SendSMS(msisdn=msisdn, message=message, validity=validity))
         d.addCallback(lambda cmd: self.wait_for_reply(cmd.msisdn))
         return d
 
-    def send_binary_message(self, msisdn, hex_message, validity=0,
+    def send_binary_message(self, msisdn, hex_message, validity='0',
                             protocol_id=PROTOCOL_STANDARD,
                             coding=CODING_7BIT):
         d = self.send_command(
@@ -128,7 +134,7 @@ def send_mms_message(self, msisdn, subject, name, content):
 
     def imsi_lookup(self, msisdn, sequence=None, imsi=None):
         if sequence is None:
-            sequence = unicode(random.randint(0, 1000))
+            sequence = str(random.randint(0, 1000))
         d = self.send_command(IMSILookup(sequence=sequence, msisdn=msisdn,
                                          imsi=imsi))
         deferred = Deferred()
diff --git a/txssmi/tests/test_protocol.py b/txssmi/tests/test_protocol.py
index 7a6ff5f..814531f 100644
--- a/txssmi/tests/test_protocol.py
+++ b/txssmi/tests/test_protocol.py
@@ -64,13 +64,13 @@ def test_authenticate(self):
         d = self.protocol.authenticate('username', 'password')
         [cmd] = yield self.receive(1)
         self.assertEqual(cmd.command_name, 'LOGIN')
-        yield self.send(Ack(ack_type=1))
+        yield self.send(Ack(ack_type='1'))
         self.assertTrue((yield d))
         self.assertTrue(self.protocol.authenticated)
 
     @inlineCallbacks
     def test_send_message(self):
-        self.protocol.send_message('2700000000', 'hi there!', validity=2)
+        self.protocol.send_message('2700000000', 'hi there!', validity='2')
         [cmd] = yield self.receive(1)
         self.assertEqual(cmd.command_name, 'SEND_SMS')
         self.assertEqual(cmd.msisdn, '2700000000')