diff --git a/IPython/parallel/apps/ipcontrollerapp.py b/IPython/parallel/apps/ipcontrollerapp.py
index 5f26e17..3b18e7a 100755
--- a/IPython/parallel/apps/ipcontrollerapp.py
+++ b/IPython/parallel/apps/ipcontrollerapp.py
@@ -197,7 +197,7 @@ class IPControllerApp(BaseParallelApplication):
                 location = socket.gethostbyname_ex(socket.gethostname())[2][-1]
             cdict['location'] = location
         fname = os.path.join(self.profile_dir.security_dir, fname)
-        with open(fname, 'w') as f:
+        with open(fname, 'wb') as f:
             f.write(json.dumps(cdict, indent=2))
         os.chmod(fname, stat.S_IRUSR|stat.S_IWUSR)
     
diff --git a/IPython/parallel/controller/hub.py b/IPython/parallel/controller/hub.py
index 01ab1eb..ab41713 100755
--- a/IPython/parallel/controller/hub.py
+++ b/IPython/parallel/controller/hub.py
@@ -250,7 +250,7 @@ class HubFactory(RegistrationFactory):
 
         # monitor socket
         sub = ctx.socket(zmq.SUB)
-        sub.setsockopt(zmq.SUBSCRIBE, "")
+        sub.setsockopt(zmq.SUBSCRIBE, b"")
         sub.bind(self.monitor_url)
         sub.bind('inproc://monitor')
         sub = ZMQStream(sub, loop)
diff --git a/IPython/parallel/controller/scheduler.py b/IPython/parallel/controller/scheduler.py
index c49f9c7..b318f39 100644
--- a/IPython/parallel/controller/scheduler.py
+++ b/IPython/parallel/controller/scheduler.py
@@ -678,7 +678,7 @@ def launch_scheduler(in_addr, out_addr, mon_addr, not_addr, config=None,
     mons = zmqstream.ZMQStream(ctx.socket(zmq.PUB),loop)
     mons.connect(mon_addr)
     nots = zmqstream.ZMQStream(ctx.socket(zmq.SUB),loop)
-    nots.setsockopt(zmq.SUBSCRIBE, '')
+    nots.setsockopt(zmq.SUBSCRIBE, b'')
     nots.connect(not_addr)
     
     # setup logging.
diff --git a/IPython/utils/tests/test_traitlets.py b/IPython/utils/tests/test_traitlets.py
index 7e4ee49..5639a50 100755
--- a/IPython/utils/tests/test_traitlets.py
+++ b/IPython/utils/tests/test_traitlets.py
@@ -704,15 +704,15 @@ class TestComplex(TraitTestBase):
 
 class BytesTrait(HasTraits):
 
-    value = Bytes('string')
+    value = Bytes(b'string')
 
 class TestBytes(TraitTestBase):
 
     obj = BytesTrait()
 
-    _default_value = 'string'
-    _good_values   = ['10', '-10', '10L',
-                      '-10L', '10.1', '-10.1', 'string']
+    _default_value = b'string'
+    _good_values   = [b'10', b'-10', b'10L',
+                      b'-10L', b'10.1', b'-10.1', b'string']
     _bad_values    = [10, -10, 10L, -10L, 10.1, -10.1, 1j, [10],
                       ['ten'],{'ten': 10},(10,), None,  u'string']
 
diff --git a/IPython/zmq/session.py b/IPython/zmq/session.py
index f4482e3..e2001a2 100644
--- a/IPython/zmq/session.py
+++ b/IPython/zmq/session.py
@@ -82,7 +82,7 @@ default_packer = json_packer
 default_unpacker = json_unpacker
 
 
-DELIM="<IDS|MSG>"
+DELIM=b"<IDS|MSG>"
 
 #-----------------------------------------------------------------------------
 # Classes