Add device discovery (#25)

* add (untested) discover mode

* Keep discovery and normal communication separate, uppercase magic consts

This sepearates the earlier test code for discovering devices,
and adds 5 sec timeout for gathering responses from potential devices.

This commit also uppercases magic constants.

Discovery & communication tested with HS110.

* update readme with example how to discover devices, pep8ify

README.md

@@ -59,3 +59,9 @@ There is also a simple tool for testing connectivity in examples, to use:
 ```python
 python -m examples.cli <ip>
 ```
+
+# Discovering devices
+```python
+python3 -m examples.discover
+```
+

examples/discover.py

@@ -0,0 +1,9 @@
+import logging
+from pprint import pprint as pp
+
+from pyHS100 import TPLinkSmartHomeProtocol
+logging.basicConfig(level=logging.DEBUG)
+
+for dev in TPLinkSmartHomeProtocol.discover():
+    print("Found device!")
+    pp(dev)

pyHS100/__init__.py

@@ -1,3 +1,3 @@
 from __future__ import absolute_import
 from __future__ import unicode_literals
-from pyHS100.pyHS100 import SmartPlug, SmartPlugException
+from pyHS100.pyHS100 import SmartPlug, TPLinkSmartHomeProtocol, SmartPlugException

pyHS100/protocol.py

@@ -21,10 +21,12 @@ class TPLinkSmartHomeProtocol:
     which are licensed under the Apache License, Version 2.0
     http://www.apache.org/licenses/LICENSE-2.0
     """
-    initialization_vector = 171
+    INITIALIZATION_VECTOR = 171
+    DEFAULT_PORT = 9999
+    DEFAULT_TIMEOUT = 5
 
     @staticmethod
-    def query(host, request, port=9999):
+    def query(host, request, port=DEFAULT_PORT):
         """
         Request information from a TP-Link SmartHome Device and return the
         response.
@@ -62,6 +64,48 @@ class TPLinkSmartHomeProtocol:
 
         return json.loads(response)
 
+    @staticmethod
+    def discover(timeout=DEFAULT_TIMEOUT, port=DEFAULT_PORT):
+        """
+        Sends discovery message to 255.255.255.255:9999 in order
+        to detect available supported devices in the local network,
+        and waits for given timeout for answers from devices.
+
+        :param timeout: How long to wait for responses, defaults to 5
+        :param port: port to send broadcast messages, defaults to 9999.
+        :rtype: list[dict]
+        :return: Array of json objects {"ip", "port", "sys_info"}
+        """
+        discovery_query = {"system": {"get_sysinfo": None},
+                           "emeter": {"get_realtime": None}}
+        target = "255.255.255.255"
+
+        sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        sock.settimeout(timeout)
+
+        req = json.dumps(discovery_query)
+        _LOGGER.debug("Sending discovery to %s:%s", target, port)
+
+        encrypted_req = TPLinkSmartHomeProtocol.encrypt(req)
+        sock.sendto(encrypted_req[4:], (target, port))
+
+        devices = []
+        _LOGGER.debug("Waiting %s seconds for responses...", timeout)
+
+        try:
+            while True:
+                data, addr = sock.recvfrom(4096)
+                ip, port = addr
+                info = json.loads(TPLinkSmartHomeProtocol.decrypt(data))
+
+                devices.append({"ip": ip, "port": port, "sys_info": info})
+        except Exception as ex:
+            _LOGGER.error("Got exception %s", ex, exc_info=True)
+
+        return devices
+
     @staticmethod
     def encrypt(request):
         """
@@ -70,7 +114,7 @@ class TPLinkSmartHomeProtocol:
         :param request: plaintext request data
         :return: ciphertext request
         """
-        key = TPLinkSmartHomeProtocol.initialization_vector
+        key = TPLinkSmartHomeProtocol.INITIALIZATION_VECTOR
         buffer = bytearray(4)  # 4 nullbytes
 
         for char in request:
@@ -88,7 +132,7 @@ class TPLinkSmartHomeProtocol:
         :param ciphertext: encrypted response data
         :return: plaintext response
         """
-        key = TPLinkSmartHomeProtocol.initialization_vector
+        key = TPLinkSmartHomeProtocol.INITIALIZATION_VECTOR
         buffer = []
 
         ciphertext = ciphertext.decode('latin-1')