Prevent TLS from closing randomly (#49)

Keep references to bare transport objects to prevent GC from deleting them prematurely, as deletion of transport objects closes underlying sockets. Such behaviour breaks write operations and totally ruins loop which listens for incoming read events from socket (see also #43)

nats/aio/client.py

@@ -10,7 +10,7 @@
 from nats.aio.utils import new_inbox
 from nats.protocol.parser import *
 
-__version__ = '0.6.2'
+__version__ = '0.6.3'
 __lang__ = 'python3'
 PROTOCOL = 1
 
@@ -104,7 +104,9 @@ def __init__(self):
         self._pings_outstanding = 0
         self._pongs_received = 0
         self._pongs = []
+        self._bare_io_reader = None
         self._io_reader = None
+        self._bare_io_writer = None
         self._io_writer = None
         self._err = None
         self._error_cb = None
@@ -582,8 +584,8 @@ def _select_next_server(self):
                     loop=self._loop,
                     limit=DEFAULT_BUFFER_SIZE)
                 srv = s
-                self._io_reader = r
-                self._io_writer = w
+                self._bare_io_reader = self._io_reader = r
+                self._bare_io_writer = self._io_writer = w
                 break
             except Exception as e:
                 self._err = e
@@ -866,6 +868,7 @@ def _process_connect_init(self):
             if not sock:
                 # This shouldn't happen
                 raise NatsError('nats: unable to get socket')
+
             yield from self._io_writer.drain()  # just in case something is left
 
             self._io_reader, self._io_writer = \