Add support for events to accessory server

[Jc2k]

This is the first step towards #51, but arguably not a complete solution. I have pulled it out of #154 so it can be reviewed in isolation. It doesn't have tests on its own (but there are tests that make use of this in #154).

If you have 2 active connections open to an accessory then a put_characteristic on connection 1 will now trigger events on connection but not its own connection (and vice versa).

This refactors the part of handle_one_request that writes a HTTP response to the wire out into its own function and ensures that only one task can write to the socket at once (otherwise there is a race when there are multiple tasks encrypting and writing to the network).

Then there is a write_event helper on the request handler that writes a single HTTP Event Response to the wire. There is a variant of this on the HTTPServer that can write an event to all active connections.

Right now events are only triggered from put_characteristic HTTP handlers. If you were writing an accessory with homekit_python you could manually call write_event on the HTTPServer when you are recording a change. To fully close #51 we should probably integrate a bit better than this, though.

To see it working I run a demoserver.py in on terminal, pair with it in another then do:

python -m homekit.get_events -f test.json -a test -c 1.10

Then in a third terminal

python -m homekit.put_characteristic -f test.json -a test -c 1.10 true

[jlusiardi]

nice one!

[jlusiardi]

One little addition:
I get an error if I do the following:

1. Start demoserver.py
2. Connect Controller A with get_events
3. Controller B toggles the light bulb a few times
4. Kill Controller A with CTRL-C
5. Toggle one more event with Controller B results in an exception in the demoserver and a hanging Controller B

----------------------------------------
Exception happened during processing of request from ('192.168.178.21', 45992)
Traceback (most recent call last):
  File "/usr/lib/python3.5/socketserver.py", line 625, in process_request_thread
    self.finish_request(request, client_address)
  File "/usr/lib/python3.5/socketserver.py", line 354, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/home/jlusiardi/Dokumente/src/homekit_python_jc2k/homekit/accessoryserver.py", line 327, in __init__
    # make connection non blocking so the select can work
  File "/usr/lib/python3.5/socketserver.py", line 681, in __init__
    self.handle()
  File "/usr/lib/python3.5/http/server.py", line 424, in handle
    self.handle_one_request()
  File "/home/jlusiardi/Dokumente/src/homekit_python_jc2k/homekit/accessoryserver.py", line 479, in handle_one_request
    ev = params['ev'] == '1'
  File "/usr/lib/python3.5/http/server.py", line 410, in handle_one_request
    method()
  File "/home/jlusiardi/Dokumente/src/homekit_python_jc2k/homekit/accessoryserver.py", line 1283, in do_PUT
  File "/home/jlusiardi/Dokumente/src/homekit_python_jc2k/homekit/accessoryserver.py", line 677, in _put_characteristics
    # 2) generate shared secret
  File "/home/jlusiardi/Dokumente/src/homekit_python_jc2k/homekit/accessoryserver.py", line 87, in write_event
    Sets the callback function for this accessory server. This will NOT be applied to all accessories registered
  File "/home/jlusiardi/Dokumente/src/homekit_python_jc2k/homekit/accessoryserver.py", line 363, in write_event
    self.log_error(' %r', e)
  File "/home/jlusiardi/Dokumente/src/homekit_python_jc2k/homekit/accessoryserver.py", line 387, in write_encrypted_bytes
    data)
  File "/usr/lib/python3.5/socket.py", line 591, in write
    self._checkClosed()
ValueError: I/O operation on closed file.
----------------------------------------

It is no problem if Controller A quits because enough events were received or due to waiting the given amount of time.

[jlusiardi]

This could do the trick:

diff --git a/homekit/accessoryserver.py b/homekit/accessoryserver.py
index 236f3b7..f026965 100644
--- a/homekit/accessoryserver.py
+++ b/homekit/accessoryserver.py
@@ -39,14 +39,13 @@ from homekit.crypto.chacha20poly1305 import chacha20_aead_decrypt, chacha20_aead
 from homekit.crypto.srp import SrpServer
 
 from homekit.exceptions import ConfigurationError, ConfigLoadingError, ConfigSavingError, FormatError, \
-    CharacteristicPermissionError
+    CharacteristicPermissionError, DisconnectedControllerError
 from homekit.http_impl import HttpStatusCodes
 from homekit.model import Accessories, Categories
 from homekit.model.characteristics import CharacteristicsTypes
 from homekit.protocol import TLV 
 from homekit.protocol.statuscodes import HapStatusCodes
 
-
 class AccessoryServer(ThreadingMixIn, HTTPServer):
     """ 
     This server makes accessories accessible via the HomeKit protocol.
@@ -81,10 +80,16 @@ class AccessoryServer(ThreadingMixIn, HTTPServer):
         HTTPServer.__init__(self, (self.data.ip, self.data.port), AccessoryRequestHandler)
 
     def write_event(self, characteristics, source=None):
+        dead_sessions = []
         for session_id, session in self.sessions.items():
             if source and session_id == source:
                 continue
-            session['handler'].write_event(characteristics)
+            try:
+                session['handler'].write_event(characteristics)
+            except DisconnectedControllerError:
+                dead_sessions.append(session_id)
+        for session_id in dead_sessions:
+            del self.sessions[session_id]
 
     def add_accessory(self, accessory):
         self.accessories.add_accessory(accessory)
@@ -384,8 +389,11 @@ class AccessoryRequestHandler(BaseHTTPRequestHandler):
                 self.server.sessions[self.session_id]['accessory_to_controller_count'] += 1
                 out_data += len_bytes + ciper_and_mac[0] + ciper_and_mac[1]
 
-            self.orig_wfile.write(out_data)
-            self.orig_wfile.flush()
+            try:
+                self.orig_wfile.write(out_data)
+                self.orig_wfile.flush()
+            except ValueError as e:
+                raise DisconnectedControllerError()
 
     def handle_one_request(self):
         """
diff --git a/homekit/exceptions.py b/homekit/exceptions.py
index ca4daf9..7a4d0cf 100644
--- a/homekit/exceptions.py
+++ b/homekit/exceptions.py
@@ -254,3 +254,9 @@ class TransportNotSupportedError(HomeKitException):
     def __init__(self, transport):
         Exception.__init__(self,
                            'Transport {t} not supported. See setup.py for required dependencies.'.format(t=transport))
+
+
+class DisconnectedControllerError(HomeKitException):
+    def __init__(self):
+        Exception.__init__(self, 'Controller has passed away')
+

What do you think?

[Jc2k]

Looks good - i have applied that change to my branch with a tiny flake8 fix.