diff --git a/paramiko/sftp_client.py b/paramiko/sftp_client.py
index 22a9a04..11b61f7 100644
--- a/paramiko/sftp_client.py
+++ b/paramiko/sftp_client.py
@@ -48,6 +48,7 @@ def _to_unicode(s):
         except UnicodeError:
             return s
 
+b_slash = b('/')
 
 class SFTPClient (BaseSFTP):
     """
@@ -185,8 +186,8 @@ class SFTPClient (BaseSFTP):
                 raise SFTPError('Expected name response')
             count = msg.get_int()
             for i in range(count):
-                filename = _to_unicode(msg.get_string())
-                longname = _to_unicode(msg.get_string())
+                filename = msg.get_text()
+                longname = msg.get_text()
                 attr = SFTPAttributes._from_msg(msg, filename, longname)
                 if (filename != '.') and (filename != '..'):
                     filelist.append(attr)
@@ -494,7 +495,7 @@ class SFTPClient (BaseSFTP):
         count = msg.get_int()
         if count != 1:
             raise SFTPError('Realpath returned %d results' % count)
-        return _to_unicode(msg.get_string())
+        return msg.get_text()
 
     def chdir(self, path):
         """
@@ -517,7 +518,7 @@ class SFTPClient (BaseSFTP):
             return
         if not stat.S_ISDIR(self.stat(path).st_mode):
             raise SFTPError(errno.ENOTDIR, "%s: %s" % (os.strerror(errno.ENOTDIR), path))
-        self._cwd = self.normalize(path).encode('utf-8')
+        self._cwd = b(self.normalize(path))
 
     def getcwd(self):
         """
@@ -530,7 +531,7 @@ class SFTPClient (BaseSFTP):
 
         @since: 1.4
         """
-        return self._cwd
+        return u(self._cwd)
 
     def putfo(self, fl, remotepath, file_size=0, callback=None, confirm=True):
         """
@@ -769,15 +770,15 @@ class SFTPClient (BaseSFTP):
         Return an adjusted path if we're emulating a "current working
         directory" for the server.
         """
-        path = bytestring(path)
+        path = b(path)
         if self._cwd is None:
             return path
         if (len(path) > 0) and (path[0] == '/'):
             # absolute path
             return path
-        if self._cwd == '/':
+        if self._cwd == b_slash:
             return self._cwd + path
-        return self._cwd + '/' + path
+        return self._cwd + b_slash + path
 
 
 class SFTP (SFTPClient):
diff --git a/paramiko/sftp_file.py b/paramiko/sftp_file.py
index 8cc7233..754d038 100644
--- a/paramiko/sftp_file.py
+++ b/paramiko/sftp_file.py
@@ -165,7 +165,7 @@ class SFTPFile (BufferedFile):
     def _write(self, data):
         # may write less than requested if it would exceed max packet size
         chunk = min(len(data), self.MAX_REQUEST_SIZE)
-        self._reqs.append(self.sftp._async_request(type(None), CMD_WRITE, self.handle, long(self._realpos), str(data[:chunk])))
+        self._reqs.append(self.sftp._async_request(type(None), CMD_WRITE, self.handle, long(self._realpos), data[:chunk]))
         if not self.pipelined or (len(self._reqs) > 100 and self.sftp.sock.recv_ready()):
             while len(self._reqs):
                 req = self._reqs.popleft()
diff --git a/paramiko/sftp_server.py b/paramiko/sftp_server.py
index 63fe5cc..19f1ab9 100644
--- a/paramiko/sftp_server.py
+++ b/paramiko/sftp_server.py
@@ -183,7 +183,7 @@ class SFTPServer (BaseSFTP, SubsystemHandler):
                 msg.add_int(item)
             elif type(item) is long:
                 msg.add_int64(item)
-            elif isinstance(item, string_types):
+            elif isinstance(item, (string_types, bytes_types)):
                 msg.add_string(item)
             elif type(item) is SFTPAttributes:
                 item._pack(msg)
@@ -196,7 +196,7 @@ class SFTPServer (BaseSFTP, SubsystemHandler):
             # must be error code
             self._send_status(request_number, handle)
             return
-        handle._set_name('hx%d' % self.next_handle)
+        handle._set_name(b('hx%d' % self.next_handle))
         self.next_handle += 1
         if folder:
             self.folder_table[handle._get_name()] = handle