Trying to init events server raises when given port is not free.

* Also fix and improve some tests.

6 files changed, 349 insertions, 37 deletions

diff --git a/src/leap/common/events/__init__.py b/src/leap/common/events/__init__.py
index d498340..388ee17 100644
--- a/src/leap/common/events/__init__.py
+++ b/src/leap/common/events/__init__.py
@@ -123,3 +123,34 @@ def signal(signal, content="", mac_method="", mac="", reqcbk=None,
     :rtype: leap.common.events.events_pb2.EventsResponse or None
     """
     return client.signal(signal, content, mac_method, mac, reqcbk, timeout)
+
+def ping_client(port, reqcbk=None, timeout=1000):
+    """
+    Ping a client running in C{port}.
+
+    :param port: the port in which the client should be listening
+    :type port: int
+    :param reqcbk: a callback to be called when a response from client is
+        received
+    :type reqcbk: function
+        callback(leap.common.events.events_pb2.EventResponse)
+    :param timeout: the timeout for synch calls
+    :type timeout: int
+    """
+    return client.ping(port, reqcbk=reqcbk, timeout=timeout)
+
+
+def ping_server(port=server.SERVER_PORT, reqcbk=None, timeout=1000):
+    """
+    Ping the server.
+
+    :param port: the port in which server should be listening
+    :type port: int
+    :param reqcbk: a callback to be called when a response from server is
+        received
+    :type reqcbk: function
+        callback(leap.common.events.events_pb2.EventResponse)
+    :param timeout: the timeout for synch calls
+    :type timeout: int
+    """
+    return server.ping(port, reqcbk=reqcbk, timeout=timeout)
diff --git a/src/leap/common/events/client.py b/src/leap/common/events/client.py
index 17fc326..587b02a 100644
--- a/src/leap/common/events/client.py
+++ b/src/leap/common/events/client.py
@@ -233,6 +233,28 @@ def signal(signal, content="", mac_method="", mac="", reqcbk=None,
     return service.signal(request, callback=reqcbk, timeout=timeout)
 
 
+def ping(port, reqcbk=None, timeout=1000):
+    """
+    Ping a client running in C{port}.
+
+    :param port: the port in which the client should be listening
+    :type port: int
+    :param reqcbk: a callback to be called when a response from client is
+        received
+    :type reqcbk: function
+        callback(leap.common.events.events_pb2.EventResponse)
+    :param timeout: the timeout for synch calls
+    :type timeout: int
+    """
+    request = proto.PingRequest()
+    service = RpcService(
+        proto.EventsClientService_Stub,
+        port,
+        'localhost')
+    logger.info("Pinging a client in port %d..." % port)
+    return service.ping(request, callback=reqcbk, timeout=timeout)
+
+
 class EventsClientService(proto.EventsClientService):
     """
     Service for receiving signal events in clients.
@@ -270,6 +292,22 @@ class EventsClientService(proto.EventsClientService):
         response.status = proto.EventResponse.OK
         done.run(response)
 
+    def ping(self, controller, request, done):
+        """
+        Reply to a ping request.
+
+        :param controller: used to mediate a single method call
+        :type controller: protobuf.socketrpc.controller.SocketRpcController
+        :param request: the request received from the client
+        :type request: leap.common.events.events_pb2.RegisterRequest
+        :param done: callback to be called when done
+        :type done: protobuf.socketrpc.server.Callback
+        """
+        logger.info("Received ping request, sending response.")
+        response = proto.EventResponse()
+        response.status = proto.EventResponse.OK
+        done.run(response)
+
 
 class EventsClientDaemon(daemon.EventsSingletonDaemon):
     """
diff --git a/src/leap/common/events/events.proto b/src/leap/common/events/events.proto
index 79a5564..b844f42 100644
--- a/src/leap/common/events/events.proto
+++ b/src/leap/common/events/events.proto
@@ -17,6 +17,9 @@
 package leap.common.events;
 option py_generic_services = true;
 
+
+// These are the events that can be signaled using the events mechanism.
+
 enum Event {
   CLIENT_SESSION_ID = 1;
   CLIENT_UID = 2;
@@ -33,6 +36,10 @@ enum Event {
   RAISE_WINDOW = 13;
 }
 
+
+// A SignalRequest is the type of the message sent from one component to request
+// that a signal be sent to every registered component.
+
 message SignalRequest {
   required Event event = 1;
   required string content = 2;
@@ -42,6 +49,10 @@ message SignalRequest {
   optional bool error_occurred = 6;
 }
 
+
+// A RegisterRequest message tells the server that a component wants to
+// be signaled whenever a specific event occurs.
+
 message RegisterRequest {
   required Event event = 1;
   required int32 port = 2;
@@ -49,6 +60,10 @@ message RegisterRequest {
   required bytes mac = 4;
 }
 
+
+// An UnregisterRequest message tells the server that a component does not
+// want to be signaled when a specific event occurs.
+
 message UnregisterRequest {
   required Event event = 1;
   required int32 port = 2;
@@ -56,6 +71,17 @@ message UnregisterRequest {
   required bytes mac = 4;
 }
 
+
+// A PingRequest message is used to find out if a server or component is
+// alive.
+
+message PingRequest {
+}
+
+
+// The EventResponse is the message sent back by server and components after
+// they receive other kinds of requests.
+
 message EventResponse {
 
   enum Status {
@@ -68,12 +94,20 @@ message EventResponse {
   optional string result = 2;
 }
 
+
+// The EventsServerService is the service provided by the server.
+
 service EventsServerService {
+  rpc ping(PingRequest) returns (EventResponse);
   rpc register(RegisterRequest) returns (EventResponse);
   rpc unregister(UnregisterRequest) returns (EventResponse);
   rpc signal(SignalRequest) returns (EventResponse);
 }
 
+
+// EventsComponentService is the service provided by components (clients).
+
 service EventsClientService {
+  rpc ping(PingRequest) returns (EventResponse);
   rpc signal(SignalRequest) returns (EventResponse);
 }
diff --git a/src/leap/common/events/events_pb2.py b/src/leap/common/events/events_pb2.py
index 3b39950..274514c 100644
--- a/src/leap/common/events/events_pb2.py
+++ b/src/leap/common/events/events_pb2.py
@@ -14,7 +14,7 @@ from google.protobuf import descriptor_pb2
 DESCRIPTOR = _descriptor.FileDescriptor(
     name='events.proto',
     package='leap.common.events',
-    serialized_pb='\n\x0c\x65vents.proto\x12\x12leap.common.events\"\x97\x01\n\rSignalRequest\x12(\n\x05\x65vent\x18\x01 \x02(\x0e\x32\x19.leap.common.events.Event\x12\x0f\n\x07\x63ontent\x18\x02 \x02(\t\x12\x12\n\nmac_method\x18\x03 \x02(\t\x12\x0b\n\x03mac\x18\x04 \x02(\x0c\x12\x12\n\nenc_method\x18\x05 \x01(\t\x12\x16\n\x0e\x65rror_occurred\x18\x06 \x01(\x08\"j\n\x0fRegisterRequest\x12(\n\x05\x65vent\x18\x01 \x02(\x0e\x32\x19.leap.common.events.Event\x12\x0c\n\x04port\x18\x02 \x02(\x05\x12\x12\n\nmac_method\x18\x03 \x02(\t\x12\x0b\n\x03mac\x18\x04 \x02(\x0c\"l\n\x11UnregisterRequest\x12(\n\x05\x65vent\x18\x01 \x02(\x0e\x32\x19.leap.common.events.Event\x12\x0c\n\x04port\x18\x02 \x02(\x05\x12\x12\n\nmac_method\x18\x03 \x02(\t\x12\x0b\n\x03mac\x18\x04 \x02(\x0c\"\x82\x01\n\rEventResponse\x12\x38\n\x06status\x18\x01 \x02(\x0e\x32(.leap.common.events.EventResponse.Status\x12\x0e\n\x06result\x18\x02 \x01(\t\"\'\n\x06Status\x12\x06\n\x02OK\x10\x01\x12\n\n\x06UNAUTH\x10\x02\x12\t\n\x05\x45RROR\x10\x03*\xe7\x02\n\x05\x45vent\x12\x15\n\x11\x43LIENT_SESSION_ID\x10\x01\x12\x0e\n\nCLIENT_UID\x10\x02\x12\x19\n\x15SOLEDAD_CREATING_KEYS\x10\x03\x12\x1e\n\x1aSOLEDAD_DONE_CREATING_KEYS\x10\x04\x12\x1a\n\x16SOLEDAD_UPLOADING_KEYS\x10\x05\x12\x1f\n\x1bSOLEDAD_DONE_UPLOADING_KEYS\x10\x06\x12\x1c\n\x18SOLEDAD_DOWNLOADING_KEYS\x10\x07\x12!\n\x1dSOLEDAD_DONE_DOWNLOADING_KEYS\x10\x08\x12\x1c\n\x18SOLEDAD_NEW_DATA_TO_SYNC\x10\t\x12\x1a\n\x16SOLEDAD_DONE_DATA_SYNC\x10\n\x12\x17\n\x13UPDATER_NEW_UPDATES\x10\x0b\x12\x19\n\x15UPDATER_DONE_UPDATING\x10\x0c\x12\x10\n\x0cRAISE_WINDOW\x10\r2\x91\x02\n\x13\x45ventsServerService\x12R\n\x08register\x12#.leap.common.events.RegisterRequest\x1a!.leap.common.events.EventResponse\x12V\n\nunregister\x12%.leap.common.events.UnregisterRequest\x1a!.leap.common.events.EventResponse\x12N\n\x06signal\x12!.leap.common.events.SignalRequest\x1a!.leap.common.events.EventResponse2e\n\x13\x45ventsClientService\x12N\n\x06signal\x12!.leap.common.events.SignalRequest\x1a!.leap.common.events.EventResponseB\x03\x90\x01\x01')
+    serialized_pb='\n\x0c\x65vents.proto\x12\x12leap.common.events\"\x97\x01\n\rSignalRequest\x12(\n\x05\x65vent\x18\x01 \x02(\x0e\x32\x19.leap.common.events.Event\x12\x0f\n\x07\x63ontent\x18\x02 \x02(\t\x12\x12\n\nmac_method\x18\x03 \x02(\t\x12\x0b\n\x03mac\x18\x04 \x02(\x0c\x12\x12\n\nenc_method\x18\x05 \x01(\t\x12\x16\n\x0e\x65rror_occurred\x18\x06 \x01(\x08\"j\n\x0fRegisterRequest\x12(\n\x05\x65vent\x18\x01 \x02(\x0e\x32\x19.leap.common.events.Event\x12\x0c\n\x04port\x18\x02 \x02(\x05\x12\x12\n\nmac_method\x18\x03 \x02(\t\x12\x0b\n\x03mac\x18\x04 \x02(\x0c\"l\n\x11UnregisterRequest\x12(\n\x05\x65vent\x18\x01 \x02(\x0e\x32\x19.leap.common.events.Event\x12\x0c\n\x04port\x18\x02 \x02(\x05\x12\x12\n\nmac_method\x18\x03 \x02(\t\x12\x0b\n\x03mac\x18\x04 \x02(\x0c\"\r\n\x0bPingRequest\"\x82\x01\n\rEventResponse\x12\x38\n\x06status\x18\x01 \x02(\x0e\x32(.leap.common.events.EventResponse.Status\x12\x0e\n\x06result\x18\x02 \x01(\t\"\'\n\x06Status\x12\x06\n\x02OK\x10\x01\x12\n\n\x06UNAUTH\x10\x02\x12\t\n\x05\x45RROR\x10\x03*\xe7\x02\n\x05\x45vent\x12\x15\n\x11\x43LIENT_SESSION_ID\x10\x01\x12\x0e\n\nCLIENT_UID\x10\x02\x12\x19\n\x15SOLEDAD_CREATING_KEYS\x10\x03\x12\x1e\n\x1aSOLEDAD_DONE_CREATING_KEYS\x10\x04\x12\x1a\n\x16SOLEDAD_UPLOADING_KEYS\x10\x05\x12\x1f\n\x1bSOLEDAD_DONE_UPLOADING_KEYS\x10\x06\x12\x1c\n\x18SOLEDAD_DOWNLOADING_KEYS\x10\x07\x12!\n\x1dSOLEDAD_DONE_DOWNLOADING_KEYS\x10\x08\x12\x1c\n\x18SOLEDAD_NEW_DATA_TO_SYNC\x10\t\x12\x1a\n\x16SOLEDAD_DONE_DATA_SYNC\x10\n\x12\x17\n\x13UPDATER_NEW_UPDATES\x10\x0b\x12\x19\n\x15UPDATER_DONE_UPDATING\x10\x0c\x12\x10\n\x0cRAISE_WINDOW\x10\r2\xdd\x02\n\x13\x45ventsServerService\x12J\n\x04ping\x12\x1f.leap.common.events.PingRequest\x1a!.leap.common.events.EventResponse\x12R\n\x08register\x12#.leap.common.events.RegisterRequest\x1a!.leap.common.events.EventResponse\x12V\n\nunregister\x12%.leap.common.events.UnregisterRequest\x1a!.leap.common.events.EventResponse\x12N\n\x06signal\x12!.leap.common.events.SignalRequest\x1a!.leap.common.events.EventResponse2\xb1\x01\n\x13\x45ventsClientService\x12J\n\x04ping\x12\x1f.leap.common.events.PingRequest\x1a!.leap.common.events.EventResponse\x12N\n\x06signal\x12!.leap.common.events.SignalRequest\x1a!.leap.common.events.EventResponseB\x03\x90\x01\x01')
 
 _EVENT = _descriptor.EnumDescriptor(
     name='Event',
@@ -77,8 +77,8 @@ _EVENT = _descriptor.EnumDescriptor(
     ],
     containing_type=None,
     options=None,
-    serialized_start=542,
-    serialized_end=901,
+    serialized_start=557,
+    serialized_end=916,
 )
 
 Event = enum_type_wrapper.EnumTypeWrapper(_EVENT)
@@ -118,8 +118,8 @@ _EVENTRESPONSE_STATUS = _descriptor.EnumDescriptor(
     ],
     containing_type=None,
     options=None,
-    serialized_start=500,
-    serialized_end=539,
+    serialized_start=515,
+    serialized_end=554,
 )
 
 
@@ -284,6 +284,27 @@ _UNREGISTERREQUEST = _descriptor.Descriptor(
 )
 
 
+_PINGREQUEST = _descriptor.Descriptor(
+    name='PingRequest',
+    full_name='leap.common.events.PingRequest',
+    filename=None,
+    file=DESCRIPTOR,
+    containing_type=None,
+    fields=[
+    ],
+    extensions=[
+    ],
+    nested_types=[],
+    enum_types=[
+    ],
+    options=None,
+    is_extendable=False,
+    extension_ranges=[],
+    serialized_start=408,
+    serialized_end=421,
+)
+
+
 _EVENTRESPONSE = _descriptor.Descriptor(
     name='EventResponse',
     full_name='leap.common.events.EventResponse',
@@ -315,8 +336,8 @@ _EVENTRESPONSE = _descriptor.Descriptor(
     options=None,
     is_extendable=False,
     extension_ranges=[],
-    serialized_start=409,
-    serialized_end=539,
+    serialized_start=424,
+    serialized_end=554,
 )
 
 _SIGNALREQUEST.fields_by_name['event'].enum_type = _EVENT
@@ -327,6 +348,7 @@ _EVENTRESPONSE_STATUS.containing_type = _EVENTRESPONSE
 DESCRIPTOR.message_types_by_name['SignalRequest'] = _SIGNALREQUEST
 DESCRIPTOR.message_types_by_name['RegisterRequest'] = _REGISTERREQUEST
 DESCRIPTOR.message_types_by_name['UnregisterRequest'] = _UNREGISTERREQUEST
+DESCRIPTOR.message_types_by_name['PingRequest'] = _PINGREQUEST
 DESCRIPTOR.message_types_by_name['EventResponse'] = _EVENTRESPONSE
 
 
@@ -351,6 +373,13 @@ class UnregisterRequest(_message.Message):
     # @@protoc_insertion_point(class_scope:leap.common.events.UnregisterRequest)
 
 
+class PingRequest(_message.Message):
+    __metaclass__ = _reflection.GeneratedProtocolMessageType
+    DESCRIPTOR = _PINGREQUEST
+
+    # @@protoc_insertion_point(class_scope:leap.common.events.PingRequest)
+
+
 class EventResponse(_message.Message):
     __metaclass__ = _reflection.GeneratedProtocolMessageType
     DESCRIPTOR = _EVENTRESPONSE
@@ -368,13 +397,22 @@ _EVENTSSERVERSERVICE = _descriptor.ServiceDescriptor(
     file=DESCRIPTOR,
     index=0,
     options=None,
-    serialized_start=904,
-    serialized_end=1177,
+    serialized_start=919,
+    serialized_end=1268,
     methods=[
         _descriptor.MethodDescriptor(
+            name='ping',
+            full_name='leap.common.events.EventsServerService.ping',
+            index=0,
+            containing_service=None,
+            input_type=_PINGREQUEST,
+            output_type=_EVENTRESPONSE,
+            options=None,
+        ),
+        _descriptor.MethodDescriptor(
             name='register',
             full_name='leap.common.events.EventsServerService.register',
-            index=0,
+            index=1,
             containing_service=None,
             input_type=_REGISTERREQUEST,
             output_type=_EVENTRESPONSE,
@@ -383,7 +421,7 @@ _EVENTSSERVERSERVICE = _descriptor.ServiceDescriptor(
         _descriptor.MethodDescriptor(
             name='unregister',
             full_name='leap.common.events.EventsServerService.unregister',
-            index=1,
+            index=2,
             containing_service=None,
             input_type=_UNREGISTERREQUEST,
             output_type=_EVENTRESPONSE,
@@ -392,7 +430,7 @@ _EVENTSSERVERSERVICE = _descriptor.ServiceDescriptor(
         _descriptor.MethodDescriptor(
             name='signal',
             full_name='leap.common.events.EventsServerService.signal',
-            index=2,
+            index=3,
             containing_service=None,
             input_type=_SIGNALREQUEST,
             output_type=_EVENTRESPONSE,
@@ -417,13 +455,22 @@ _EVENTSCLIENTSERVICE = _descriptor.ServiceDescriptor(
     file=DESCRIPTOR,
     index=1,
     options=None,
-    serialized_start=1179,
-    serialized_end=1280,
+    serialized_start=1271,
+    serialized_end=1448,
     methods=[
         _descriptor.MethodDescriptor(
+            name='ping',
+            full_name='leap.common.events.EventsClientService.ping',
+            index=0,
+            containing_service=None,
+            input_type=_PINGREQUEST,
+            output_type=_EVENTRESPONSE,
+            options=None,
+        ),
+        _descriptor.MethodDescriptor(
             name='signal',
             full_name='leap.common.events.EventsClientService.signal',
-            index=0,
+            index=1,
             containing_service=None,
             input_type=_SIGNALREQUEST,
             output_type=_EVENTRESPONSE,
diff --git a/src/leap/common/events/server.py b/src/leap/common/events/server.py
index 8a0d4e5..daccc61 100644
--- a/src/leap/common/events/server.py
+++ b/src/leap/common/events/server.py
@@ -48,6 +48,13 @@ SERVER_PORT = 8090
 registered_clients = {}
 
 
+class PortAlreadyTaken(Exception):
+    """
+    Raised when trying to open a server in a port that is already taken.
+    """
+    pass
+
+
 def ensure_server(port=SERVER_PORT):
     """
     Make sure the server is running on the given port.
@@ -60,18 +67,51 @@ def ensure_server(port=SERVER_PORT):
 
     :return: the daemon instance or nothing
     :rtype: EventsServerDaemon or None
+
+    :raise PortAlreadyTaken: Raised if C{port} is already taken by something
+        that is not an events server.
     """
     try:
+        # check if port is available
         s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
         s.connect(('localhost', port))
         s.close()
-        logger.info('Server is already running on port %d.', port)
-        return None
+        # port is taken, check if there's a server running there
+        response = ping(port)
+        if response is not None and response.status == proto.EventResponse.OK:
+            logger.info('A server is already running on port %d.', port)
+            return None
+        # port is taken, and not by an events server
+        logger.info('Port %d is taken by something not an events server.', port)
+        raise PortAlreadyTaken(port)
     except socket.error:
+        # port is available, run a server
         logger.info('Launching server on port %d.', port)
         return EventsServerDaemon.ensure(port)
 
 
+def ping(port=SERVER_PORT, reqcbk=None, timeout=1000):
+    """
+    Ping the server.
+
+    :param port: the port in which server should be listening
+    :type port: int
+    :param reqcbk: a callback to be called when a response from server is
+        received
+    :type reqcbk: function
+        callback(leap.common.events.events_pb2.EventResponse)
+    :param timeout: the timeout for synch calls
+    :type timeout: int
+    """
+    request = proto.PingRequest()
+    service = RpcService(
+        proto.EventsServerService_Stub,
+        port,
+        'localhost')
+    logger.info("Pinging server in port %d..." % port)
+    return service.ping(request, callback=reqcbk, timeout=timeout)
+
+
 class EventsServerService(proto.EventsServerService):
     """
     Service for receiving events in clients.
@@ -156,6 +196,22 @@ class EventsServerService(proto.EventsServerService):
         response.status = proto.EventResponse.OK
         done.run(response)
 
+    def ping(self, controller, request, done):
+        """
+        Reply to a ping request.
+
+        :param controller: used to mediate a single method call
+        :type controller: protobuf.socketrpc.controller.SocketRpcController
+        :param request: the request received from the client
+        :type request: leap.common.events.events_pb2.RegisterRequest
+        :param done: callback to be called when done
+        :type done: protobuf.socketrpc.server.Callback
+        """
+        logger.info("Received ping request, sending response.")
+        response = proto.EventResponse()
+        response.status = proto.EventResponse.OK
+        done.run(response)
+
 
 class EventsServerDaemon(daemon.EventsSingletonDaemon):
     """
diff --git a/src/leap/common/tests/test_events.py b/src/leap/common/tests/test_events.py
index 687195f..90124b4 100644
--- a/src/leap/common/tests/test_events.py
+++ b/src/leap/common/tests/test_events.py
@@ -18,6 +18,12 @@
 import unittest
 import sets
 import time
+import socket
+import threading
+import random
+
+
+from mock import Mock
 from protobuf.socketrpc import RpcService
 from leap.common import events
 from leap.common.events import (
@@ -28,9 +34,11 @@ from leap.common.events import (
 from leap.common.events.events_pb2 import (
     EventsServerService,
     EventsServerService_Stub,
+    EventsClientService_Stub,
     EventResponse,
     SignalRequest,
     RegisterRequest,
+    PingRequest,
     SOLEDAD_CREATING_KEYS,
     CLIENT_UID,
 )
@@ -39,11 +47,6 @@ from leap.common.events.events_pb2 import (
 port = 8090
 
 received = False
-local_callback_executed = False
-
-
-def callback(request, reponse):
-    return True
 
 
 class EventsTestCase(unittest.TestCase):
@@ -120,17 +123,28 @@ class EventsTestCase(unittest.TestCase):
         response = service.signal(request, timeout=1000)
         self.assertEqual(EventResponse.OK, response.status,
                          'Wrong response status.')
-        # test asynch
 
-        def local_callback(request, response):
-            global local_callback_executed
-            local_callback_executed = True
+    def test_signal_executes_callback(self):
+        """
+        Ensure callback is executed upon receiving signal.
+        """
+        sig = CLIENT_UID
+        request = SignalRequest()
+        request.event = sig
+        request.content = 'my signal contents'
+        request.mac_method = mac_auth.MacMethod.MAC_NONE
+        request.mac = ""
+        service = RpcService(EventsServerService_Stub, port, 'localhost')
 
-        events.register(sig, local_callback)
-        service.signal(request, callback=local_callback)
-        time.sleep(0.1)
-        self.assertTrue(local_callback_executed,
-                        'Local callback did not execute.')
+        # register a callback
+        flag = Mock()
+        events.register(sig, lambda req: flag(req.event))
+        # signal
+        response = service.signal(request)
+        self.assertEqual(EventResponse.OK, response.status,
+                         'Wrong response status.')
+        time.sleep(1)  # wait for signal to arrive
+        flag.assert_called_once_with(sig)
 
     def test_events_server_service_register(self):
         """
@@ -173,12 +187,9 @@ class EventsTestCase(unittest.TestCase):
         Ensure clients can receive signals.
         """
         sig = 7
+        flag = Mock()
 
-        def getsig(param=None):
-            global received
-            received = True
-
-        events.register(sig, getsig)
+        events.register(sig, lambda req: flag(req.event))
         request = SignalRequest()
         request.event = sig
         request.content = ""
@@ -188,7 +199,7 @@ class EventsTestCase(unittest.TestCase):
         response = service.signal(request, timeout=1000)
         self.assertTrue(response is not None, 'Did not receive response.')
         time.sleep(0.5)
-        self.assertTrue(received, 'Did not receive signal back.')
+        flag.assert_called_once_with(sig)
 
     def test_client_send_signal(self):
         """
@@ -231,3 +242,98 @@ class EventsTestCase(unittest.TestCase):
         self.assertTrue(
             client.registered_callbacks[sig].pop()[0] == 'cbkuid2')
         self.assertTrue(port in complist[sig])
+
+    def test_server_replies_ping(self):
+        """
+        Ensure server replies to a ping.
+        """
+        request = PingRequest()
+        service = RpcService(EventsServerService_Stub, port, 'localhost')
+        response = service.ping(request, timeout=1000)
+        self.assertIsNotNone(response)
+        self.assertEqual(EventResponse.OK, response.status,
+                         'Wrong response status.')
+
+    def test_client_replies_ping(self):
+        """
+        Ensure clients reply to a ping.
+        """
+        daemon = client.ensure_client_daemon()
+        port = daemon.get_port()
+        request = PingRequest()
+        service = RpcService(EventsClientService_Stub, port, 'localhost')
+        response = service.ping(request, timeout=1000)
+        self.assertEqual(EventResponse.OK, response.status,
+                         'Wrong response status.')
+
+    def test_server_ping(self):
+        """
+        Ensure the function from server module pings correctly.
+        """
+        response = server.ping()
+        self.assertIsNotNone(response)
+        self.assertEqual(EventResponse.OK, response.status,
+                         'Wrong response status.')
+
+    def test_client_ping(self):
+        """
+        Ensure the function from client module pings correctly.
+        """
+        daemon = client.ensure_client_daemon()
+        response = client.ping(daemon.get_port())
+        self.assertIsNotNone(response)
+        self.assertEqual(EventResponse.OK, response.status,
+                         'Wrong response status.')
+
+    def test_module_ping_server(self):
+        """
+        Ensure the function from main module pings server correctly.
+        """
+        response = events.ping_server()
+        self.assertIsNotNone(response)
+        self.assertEqual(EventResponse.OK, response.status,
+                         'Wrong response status.')
+
+    def test_module_ping_client(self):
+        """
+        Ensure the function from main module pings clients correctly.
+        """
+        daemon = client.ensure_client_daemon()
+        response = events.ping_client(daemon.get_port())
+        self.assertIsNotNone(response)
+        self.assertEqual(EventResponse.OK, response.status,
+                         'Wrong response status.')
+
+    def test_ensure_server_raises_if_port_taken(self):
+        """
+        Verify that server raises an exception if port is already taken.
+        """
+        # get a random free port
+        while True:
+            port = random.randint(1024, 65535)
+            try:
+                s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+                s.connect(('localhost', port))
+                s.close()
+            except:
+                break
+
+        class PortBlocker(threading.Thread):
+
+            def run(self):
+                conns = 0
+                s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+                s.bind(('localhost', port))
+                s.setblocking(1)
+                s.listen(1)
+                while conns < 2:  # blocks until rece
+                    conns += 1
+                    s.accept()
+                s.close()
+
+        # block the port
+        taker = PortBlocker()
+        taker.start()
+        time.sleep(1)  # wait for thread to start.
+        self.assertRaises(
+            server.PortAlreadyTaken, server.ensure_server, port)