diff --git a/steam/client/__init__.py b/steam/client/__init__.py
index 9e48a8e..d3d317f 100644
--- a/steam/client/__init__.py
+++ b/steam/client/__init__.py
@@ -239,7 +239,7 @@ class SteamClient(EventEmitter, FeatureBase):
 
         if filepath and os.path.isfile(filepath):
             try:
-                with open(filepath, 'r') as f:
+                with open(filepath, 'rb') as f:
                     return f.read()
             except IOError as e:
                 logger.error("get_sentry: %s" % str(e))
@@ -258,7 +258,7 @@ class SteamClient(EventEmitter, FeatureBase):
         filepath = self._get_sentry_path(username)
         if filepath:
             try:
-                with open(filepath, 'w') as f:
+                with open(filepath, 'wb') as f:
                     f.write(sentry_bytes)
                 return True
             except IOError as e:
diff --git a/steam/core/cm.py b/steam/core/cm.py
index e6f33fa..3e2e809 100644
--- a/steam/core/cm.py
+++ b/steam/core/cm.py
@@ -5,10 +5,7 @@ import zipfile
 from time import time
 from collections import defaultdict
 
-try:
-    from cStringIO import StringIO
-except ImportError:
-    from StringIO import StringIO
+from io import BytesIO
 
 import gevent
 from gevent import event, queue
@@ -266,7 +263,7 @@ class CMClient(EventEmitter):
         if msg.body.size_unzipped:
             logger.debug("Unzipping body")
 
-            data = zipfile.ZipFile(StringIO(msg.body.message_body)).read('z')
+            data = zipfile.ZipFile(BytesIO(msg.body.message_body)).read('z')
 
             if len(data) != msg.body.size_unzipped:
                 logger.fatal("Unzipped size mismatch")
@@ -415,7 +412,7 @@ class CMServerList(object):
     def __iter__(self):
         def genfunc():
             while True:
-                good_servers = filter(lambda x: x[1]['quality'] == CMServerList.Good, self.list.items())
+                good_servers = list(filter(lambda x: x[1]['quality'] == CMServerList.Good, self.list.items()))
 
                 if len(good_servers) == 0:
                     self.reset_all()
diff --git a/steam/core/connection.py b/steam/core/connection.py
index 6b8f579..8dfcfef 100644
--- a/steam/core/connection.py
+++ b/steam/core/connection.py
@@ -11,7 +11,7 @@ logger = logging.getLogger("Connection")
 
 
 class Connection(object):
-    MAGIC = 'VT01'
+    MAGIC = b'VT01'
     FMT = '<I4s'
     FMT_SIZE = struct.calcsize(FMT)
 
@@ -22,7 +22,7 @@ class Connection(object):
 
         self._reader = None
         self._writer = None
-        self._readbuf = ''
+        self._readbuf = b''
         self.send_queue = queue.Queue()
         self.recv_queue = queue.Queue()
 
@@ -61,7 +61,7 @@ class Connection(object):
             self._writer.kill(block=False)
             self._writer = None
 
-        self._readbuf = ''
+        self._readbuf = b''
         self.send_queue.queue.clear()
         self.recv_queue.queue.clear()
         self.recv_queue.put(StopIteration)