Merge remote-tracking branch 'drebs/feature/3246-refactor-events-so-components-become-clients' into develop

8 files changed, 617 insertions, 167 deletions

diff --git a/src/leap/common/events/README.rst b/src/leap/common/events/README.rst
index 813be8b..2e7f254 100644
--- a/src/leap/common/events/README.rst
+++ b/src/leap/common/events/README.rst
@@ -1,19 +1,19 @@
 Events mechanism
 ================
 
-The events mechanism allows for "components" to send signal events to each
-other by means of a centralized server. Components can register with the
+The events mechanism allows for clients to send signal events to each
+other by means of a centralized server. Clients can register with the
 server to receive signals of certain types, and they can also send signals to
-the server that will then redistribute these signals to registered components.
+the server that will then redistribute these signals to registered clients.
 
 
 Listening daemons
 -----------------
 
-Both components and the server listen for incoming messages by using a
+Both clients and the server listen for incoming messages by using a
 listening daemon that runs in its own thread. The server daemon has to be
-started explicitly, while components daemon will be started whenever a
-component registers with the server to receive messages.
+started explicitly, while clients daemon will be started whenever a
+client registers with the server to receive messages.
 
 
 How to use it
diff --git a/src/leap/common/events/__init__.py b/src/leap/common/events/__init__.py
index 12416e4..a6fe7c3 100644
--- a/src/leap/common/events/__init__.py
+++ b/src/leap/common/events/__init__.py
@@ -16,7 +16,58 @@
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 
 """
-An events mechanism that allows for signaling of events between components.
+This is an events mechanism that uses a server to allow for signaling of
+events between clients.
+
+Application components should use the interface available in this file to
+register callbacks to be executed upon receiving specific signals, and to send
+signals to other components.
+
+To register a callback to be executed when a specific event is signaled, use
+leap.common.events.register():
+
+>>> from leap.common.events import register
+>>> from leap.common.events.proto import CLIENT_UID
+>>> register(CLIENT_UID, lambda req: do_something(req))
+
+To signal an event, use leap.common.events.signal():
+
+>>> from leap.common.events import signal
+>>> from leap.common.events.proto import CLIENT_UID
+>>> signal(CLIENT_UID)
+
+
+NOTE ABOUT SYNC/ASYNC REQUESTS:
+
+Clients always communicate with the server, and never between themselves.
+When a client registers a callback for an event, the callback is saved locally
+in the client and the server stores the client socket port in a list
+associated with that event. When a client signals an event, the server
+forwards the signal to all registered client ports, and then each client
+executes its callbacks associated with that event locally.
+
+Each RPC call from a client to the server is followed by a response from the
+server to the client. Calls to register() and signal() (and all other RPC
+calls) can be synchronous or asynchronous meaning if they will or not wait for
+the server's response before returning.
+
+This mechanism was built on top of protobuf.socketrpc, and because of this RPC
+calls are made synchronous or asynchronous in the following way:
+
+  * If RPC calls receive a parameter called `reqcbk`, then the call is made
+    asynchronous. That means that:
+
+        - an eventual `timeout` parameter is not used,
+        - the call returns immediatelly with value None, and
+        - the `reqcbk` callback is executed asynchronously upon the arrival of
+          a response from the server.
+
+  * Otherwise, if the `reqcbk` parameter is None, then the call is made in a
+    synchronous manner:
+
+        - if a response from server arrives within `timeout` milliseconds, the
+          RPC call returns it;
+        - otherwise, the call returns None.
 """
 
 import logging
@@ -26,7 +77,7 @@ import socket
 from leap.common.events import (
     events_pb2 as proto,
     server,
-    component,
+    client,
     daemon,
 )
 
@@ -54,9 +105,8 @@ def register(signal, callback, uid=None, replace=False, reqcbk=None,
     :param replace: should an existent callback with same uid be replaced?
     :type replace: bool
     :param reqcbk: a callback to be called when a response from server is
-        received
-    :type reqcbk: function
-        callback(leap.common.events.events_pb2.EventResponse)
+                   received
+    :type reqcbk: function(leap.common.events.events_pb2.EventResponse)
     :param timeout: the timeout for synch calls
     :type timeout: int
 
@@ -64,7 +114,7 @@ def register(signal, callback, uid=None, replace=False, reqcbk=None,
         calls.
     :rtype: leap.common.events.events_pb2.EventsResponse or None
     """
-    return component.register(signal, callback, uid, replace, reqcbk, timeout)
+    return client.register(signal, callback, uid, replace, reqcbk, timeout)
 
 
 def unregister(signal, uid=None, reqcbk=None, timeout=1000):
@@ -79,17 +129,16 @@ def unregister(signal, uid=None, reqcbk=None, timeout=1000):
     :param uid: a unique id for the callback
     :type uid: 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)
+                   received
+    :type reqcbk: function(leap.common.events.events_pb2.EventResponse)
     :param timeout: the timeout for synch calls
     :type timeout: int
 
     :return: the response from server for synch calls or nothing for asynch
-        calls.
+             calls.
     :rtype: leap.common.events.events_pb2.EventsResponse or None
     """
-    return component.unregister(signal, uid, reqcbk, timeout)
+    return client.unregister(signal, uid, reqcbk, timeout)
 
 
 def signal(signal, content="", mac_method="", mac="", reqcbk=None,
@@ -112,14 +161,42 @@ def signal(signal, content="", mac_method="", mac="", reqcbk=None,
     :param mac: the content of the auth mac
     :type mac: str
     :param reqcbk: a callback to be called when a response from server is
-        received
-    :type reqcbk: function
-        callback(leap.common.events.events_pb2.EventResponse)
+                   received
+    :type reqcbk: function(leap.common.events.events_pb2.EventResponse)
     :param timeout: the timeout for synch calls
     :type timeout: int
 
     :return: the response from server for synch calls or nothing for asynch
-        calls.
+             calls.
     :rtype: leap.common.events.events_pb2.EventsResponse or None
     """
-    return component.signal(signal, content, mac_method, mac, reqcbk, timeout)
+    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(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(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/component.py b/src/leap/common/events/client.py
index 029d1ac..55f14ab 100644
--- a/src/leap/common/events/component.py
+++ b/src/leap/common/events/client.py
@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-# component.py
+# client.py
 # Copyright (C) 2013 LEAP
 #
 # This program is free software: you can redistribute it and/or modify
@@ -16,15 +16,15 @@
 # along with this program. If not, see <http://www.gnu.org/licenses/>.
 
 """
-The component end point of the events mechanism.
+The client end point of the events mechanism.
 
-Components are the communicating parties of the events mechanism. They
+Clients are the communicating parties of the events mechanism. They
 communicate by sending messages to a server, which in turn redistributes
-messages to other components.
+messages to other clients.
 
-When a component registers a callback for a given signal, it also tells the
+When a client registers a callback for a given signal, it also tells the
 server that it wants to be notified whenever signals of that type are sent by
-some other component.
+some other client.
 """
 
 
@@ -59,23 +59,23 @@ class CallbackAlreadyRegistered(Exception):
     pass
 
 
-def ensure_component_daemon():
+def ensure_client_daemon():
     """
-    Ensure the component daemon is running and listening for incoming
+    Ensure the client daemon is running and listening for incoming
     messages.
 
     :return: the daemon instance
-    :rtype: EventsComponentDaemon
+    :rtype: EventsClientDaemon
     """
     import time
-    daemon = EventsComponentDaemon.ensure(0)
-    logger.debug('ensure component daemon')
+    daemon = EventsClientDaemon.ensure(0)
+    logger.debug('ensure client daemon')
 
     # Because we use a random port we want to wait until a port is assigned to
-    # local component daemon.
+    # local client daemon.
 
-    while not (EventsComponentDaemon.get_instance() and
-               EventsComponentDaemon.get_instance().get_port()):
+    while not (EventsClientDaemon.get_instance() and
+               EventsClientDaemon.get_instance().get_port()):
         time.sleep(0.1)
     return daemon
 
@@ -95,16 +95,14 @@ def register(signal, callback, uid=None, replace=False, reqcbk=None,
     :param signal: the signal that causes the callback to be launched
     :type signal: int (see the `events.proto` file)
     :param callback: the callback to be called when the signal is received
-    :type callback: function
-        callback(leap.common.events.events_pb2.SignalRequest)
+    :type callback: function(leap.common.events.events_pb2.SignalRequest)
     :param uid: a unique id for the callback
     :type uid: int
     :param replace: should an existent callback with same uid be replaced?
     :type replace: bool
     :param reqcbk: a callback to be called when a response from server is
-        received
-    :type reqcbk: function
-        callback(leap.common.events.events_pb2.EventResponse)
+                   received
+    :type reqcbk: function(leap.common.events.events_pb2.EventResponse)
     :param timeout: the timeout for synch calls
     :type timeout: int
 
@@ -112,10 +110,10 @@ def register(signal, callback, uid=None, replace=False, reqcbk=None,
     callback identified by the given uid and replace is False.
 
     :return: the response from server for synch calls or nothing for asynch
-        calls.
+             calls.
     :rtype: leap.common.events.events_pb2.EventsResponse or None
     """
-    ensure_component_daemon()  # so we can receive registered signals
+    ensure_client_daemon()  # so we can receive registered signals
     # register callback locally
     if signal not in registered_callbacks:
         registered_callbacks[signal] = []
@@ -130,7 +128,7 @@ def register(signal, callback, uid=None, replace=False, reqcbk=None,
     # register callback on server
     request = proto.RegisterRequest()
     request.event = signal
-    request.port = EventsComponentDaemon.get_instance().get_port()
+    request.port = EventsClientDaemon.get_instance().get_port()
     request.mac_method = mac_auth.MacMethod.MAC_NONE
     request.mac = ""
     service = RpcService(proto.EventsServerService_Stub,
@@ -153,14 +151,14 @@ def unregister(signal, uid=None, reqcbk=None, timeout=1000):
     :param uid: a unique id for the callback
     :type uid: 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)
+                   received
+    :type reqcbk: function(leap.common.events.events_pb2.EventResponse)
     :param timeout: the timeout for synch calls
     :type timeout: int
 
     :return: the response from server for synch calls or nothing for asynch
-        calls or None if no callback is registered for that signal or uid.
+             calls or None if no callback is registered for that signal or
+             uid.
     :rtype: leap.common.events.events_pb2.EventsResponse or None
     """
     if signal not in registered_callbacks or not registered_callbacks[signal]:
@@ -180,7 +178,7 @@ def unregister(signal, uid=None, reqcbk=None, timeout=1000):
     if not registered_callbacks[signal]:
         request = proto.UnregisterRequest()
         request.event = signal
-        request.port = EventsComponentDaemon.get_instance().get_port()
+        request.port = EventsClientDaemon.get_instance().get_port()
         request.mac_method = mac_auth.MacMethod.MAC_NONE
         request.mac = ""
         service = RpcService(proto.EventsServerService_Stub,
@@ -212,14 +210,13 @@ def signal(signal, content="", mac_method="", mac="", reqcbk=None,
     :param mac: the content of the auth mac
     :type mac: str
     :param reqcbk: a callback to be called when a response from server is
-        received
-    :type reqcbk: function
-        callback(leap.common.events.events_pb2.EventResponse)
+                   received
+    :type reqcbk: function(leap.common.events.events_pb2.EventResponse)
     :param timeout: the timeout for synch calls
     :type timeout: int
 
     :return: the response from server for synch calls or nothing for asynch
-        calls.
+             calls.
     :rtype: leap.common.events.events_pb2.EventsResponse or None
     """
     request = proto.SignalRequest()
@@ -233,13 +230,38 @@ def signal(signal, content="", mac_method="", mac="", reqcbk=None,
     return service.signal(request, callback=reqcbk, timeout=timeout)
 
 
-class EventsComponentService(proto.EventsComponentService):
+def ping(port, reqcbk=None, timeout=1000):
     """
-    Service for receiving signal events in components.
+    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(leap.common.events.events_pb2.EventResponse)
+    :param timeout: the timeout for synch calls
+    :type timeout: int
+
+    :return: the response from client for synch calls or nothing for asynch
+             calls.
+    :rtype: leap.common.events.events_pb2.EventsResponse or None
+    """
+    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.
     """
 
     def __init__(self):
-        proto.EventsComponentService.__init__(self)
+        proto.EventsClientService.__init__(self)
 
     def signal(self, controller, request, done):
         """
@@ -250,7 +272,7 @@ class EventsComponentService(proto.EventsComponentService):
 
         :param controller: used to mediate a single method call
         :type controller: protobuf.socketrpc.controller.SocketRpcController
-        :param request: the request received from the component
+        :param request: the request received from the client
         :type request: leap.common.events.events_pb2.SignalRequest
         :param done: callback to be called when done
         :type done: protobuf.socketrpc.server.Callback
@@ -270,8 +292,24 @@ class EventsComponentService(proto.EventsComponentService):
         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 EventsComponentDaemon(daemon.EventsSingletonDaemon):
+class EventsClientDaemon(daemon.EventsSingletonDaemon):
     """
     A daemon that listens for incoming events from server.
     """
@@ -285,6 +323,6 @@ class EventsComponentDaemon(daemon.EventsSingletonDaemon):
         :type port: int
 
         :return: a daemon instance
-        :rtype: EventsComponentDaemon
+        :rtype: EventsClientDaemon
         """
-        return cls.ensure_service(port, EventsComponentService())
+        return cls.ensure_service(port, EventsClientService())
diff --git a/src/leap/common/events/daemon.py b/src/leap/common/events/daemon.py
index c253948..c4a4189 100644
--- a/src/leap/common/events/daemon.py
+++ b/src/leap/common/events/daemon.py
@@ -43,7 +43,7 @@ class ServiceAlreadyRunningException(Exception):
 
 class EventsRpcServer(SocketRpcServer):
     """
-    RPC server used in server and component interfaces to receive messages.
+    RPC server used in server and client interfaces to receive messages.
     """
 
     def __init__(self, port, host='localhost'):
diff --git a/src/leap/common/events/events.proto b/src/leap/common/events/events.proto
index a813ed1..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);
 }
 
-service EventsComponentService {
+
+// 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 5b1c118..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.EventResponse2h\n\x16\x45ventsComponentService\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,
@@ -411,20 +449,29 @@ class EventsServerService_Stub(EventsServerService):
     DESCRIPTOR = _EVENTSSERVERSERVICE
 
 
-_EVENTSCOMPONENTSERVICE = _descriptor.ServiceDescriptor(
-    name='EventsComponentService',
-    full_name='leap.common.events.EventsComponentService',
+_EVENTSCLIENTSERVICE = _descriptor.ServiceDescriptor(
+    name='EventsClientService',
+    full_name='leap.common.events.EventsClientService',
     file=DESCRIPTOR,
     index=1,
     options=None,
-    serialized_start=1179,
-    serialized_end=1283,
+    serialized_start=1271,
+    serialized_end=1448,
     methods=[
         _descriptor.MethodDescriptor(
-            name='signal',
-            full_name='leap.common.events.EventsComponentService.signal',
+            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=1,
+            containing_service=None,
             input_type=_SIGNALREQUEST,
             output_type=_EVENTRESPONSE,
             options=None,
@@ -432,13 +479,13 @@ _EVENTSCOMPONENTSERVICE = _descriptor.ServiceDescriptor(
     ])
 
 
-class EventsComponentService(_service.Service):
+class EventsClientService(_service.Service):
     __metaclass__ = service_reflection.GeneratedServiceType
-    DESCRIPTOR = _EVENTSCOMPONENTSERVICE
+    DESCRIPTOR = _EVENTSCLIENTSERVICE
 
 
-class EventsComponentService_Stub(EventsComponentService):
+class EventsClientService_Stub(EventsClientService):
     __metaclass__ = service_reflection.GeneratedServiceStubType
-    DESCRIPTOR = _EVENTSCOMPONENTSERVICE
+    DESCRIPTOR = _EVENTSCLIENTSERVICE
 
 # @@protoc_insertion_point(module_scope)
diff --git a/src/leap/common/events/server.py b/src/leap/common/events/server.py
index d53c218..a7d4da9 100644
--- a/src/leap/common/events/server.py
+++ b/src/leap/common/events/server.py
@@ -17,12 +17,12 @@
 """
 A server for the events mechanism.
 
-A server can receive different kinds of requests from components:
+A server can receive different kinds of requests from clients:
 
-  1. Registration request: store component port number to be notified when
+  1. Registration request: store client port number to be notified when
      a specific signal arrives.
 
-  2. Signal request: redistribute the signal to registered components.
+  2. Signal request: redistribute the signal to registered clients.
 """
 import logging
 import socket
@@ -40,12 +40,19 @@ logger = logging.getLogger(__name__)
 
 SERVER_PORT = 8090
 
-# the `registered_components` dictionary below should have the following
+# the `registered_clients` dictionary below should have the following
 # format:
 #
 #     { event_signal: [ port, ... ], ... }
 #
-registered_components = {}
+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):
@@ -60,40 +67,76 @@ 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(leap.common.events.events_pb2.EventResponse)
+    :param timeout: the timeout for synch calls
+    :type timeout: int
+
+    :return: the response from server for synch calls or nothing for asynch
+             calls.
+    :rtype: leap.common.events.events_pb2.EventsResponse or None
+    """
+    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 components.
+    Service for receiving events in clients.
     """
 
     def register(self, controller, request, done):
         """
-        Register a component port to be signaled when specific events come in.
+        Register a client port to be signaled when specific events come in.
 
         :param controller: used to mediate a single method call
         :type controller: protobuf.socketrpc.controller.SocketRpcController
-        :param request: the request received from the component
+        :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 registration request: %s..." % str(request)[:40])
-        # add component port to signal list
-        if request.event not in registered_components:
-            registered_components[request.event] = set([])
-        registered_components[request.event].add(request.port)
-        # send response back to component
+        # add client port to signal list
+        if request.event not in registered_clients:
+            registered_clients[request.event] = set([])
+        registered_clients[request.event].add(request.port)
+        # send response back to client
 
         logger.debug('sending response back')
         response = proto.EventResponse()
@@ -102,56 +145,72 @@ class EventsServerService(proto.EventsServerService):
 
     def unregister(self, controller, request, done):
         """
-        Unregister a component port so it will not be signaled when specific
+        Unregister a client port so it will not be signaled when specific
         events come in.
 
         :param controller: used to mediate a single method call
         :type controller: protobuf.socketrpc.controller.SocketRpcController
-        :param request: the request received from the component
+        :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 unregistration request: %s..." % str(request)[:40])
-        # remove component port from signal list
+        # remove client port from signal list
         response = proto.EventResponse()
-        if request.event in registered_components:
+        if request.event in registered_clients:
             try:
-                registered_components[request.event].remove(request.port)
+                registered_clients[request.event].remove(request.port)
                 response.status = proto.EventResponse.OK
             except KeyError:
                 response.status = proto.EventsResponse.ERROR
                 response.result = 'Port %d not registered.' % request.port
-        # send response back to component
+        # send response back to client
         logger.debug('sending response back')
         done.run(response)
 
     def signal(self, controller, request, done):
         """
-        Perform an RPC call to signal all components registered to receive a
+        Perform an RPC call to signal all clients registered to receive a
         specific signal.
 
         :param controller: used to mediate a single method call
         :type controller: protobuf.socketrpc.controller.SocketRpcController
-        :param request: the request received from the component
+        :param request: the request received from the client
         :type request: leap.common.events.events_pb2.SignalRequest
         :param done: callback to be called when done
         :type done: protobuf.socketrpc.server.Callback
         """
-        logger.info('Received signal from component: %s...', str(request)[:40])
-        # send signal to all registered components
+        logger.info('Received signal from client: %s...', str(request)[:40])
+        # send signal to all registered clients
         # TODO: verify signal auth
-        if request.event in registered_components:
-            for port in registered_components[request.event]:
+        if request.event in registered_clients:
+            for port in registered_clients[request.event]:
 
                 def callback(req, resp):
                     logger.info("Signal received by " + str(port))
 
-                service = RpcService(proto.EventsComponentService_Stub,
+                service = RpcService(proto.EventsClientService_Stub,
                                      port, 'localhost')
                 service.signal(request, callback=callback)
-        # send response back to component
+        # send response back to client
+        response = proto.EventResponse()
+        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)
diff --git a/src/leap/common/tests/test_events.py b/src/leap/common/tests/test_events.py
index 7286bdc..bc04dd6 100644
--- a/src/leap/common/tests/test_events.py
+++ b/src/leap/common/tests/test_events.py
@@ -18,19 +18,27 @@
 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 (
     server,
-    component,
+    client,
     mac_auth,
 )
 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):
@@ -51,7 +54,7 @@ class EventsTestCase(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
         server.EventsServerDaemon.ensure(8090)
-        cls.callbacks = events.component.registered_callbacks
+        cls.callbacks = events.client.registered_callbacks
 
     @classmethod
     def tearDownClass(cls):
@@ -62,8 +65,8 @@ class EventsTestCase(unittest.TestCase):
         super(EventsTestCase, self).setUp()
 
     def tearDown(self):
-        #events.component.registered_callbacks = {}
-        server.registered_components = {}
+        #events.client.registered_callbacks = {}
+        server.registered_clients = {}
         super(EventsTestCase, self).tearDown()
 
     def test_service_singleton(self):
@@ -76,24 +79,24 @@ class EventsTestCase(unittest.TestCase):
         self.assertEqual(service1, service2,
                          "Can't get singleton class for service.")
 
-    def test_component_register(self):
+    def test_client_register(self):
         """
-        Ensure components can register callbacks.
+        Ensure clients can register callbacks.
         """
         self.assertTrue(1 not in self.callbacks,
                         'There should should be no callback for this signal.')
         events.register(1, lambda x: True)
         self.assertTrue(1 in self.callbacks,
-                        'Could not register signal in local component.')
+                        'Could not register signal in local client.')
         events.register(2, lambda x: True)
         self.assertTrue(1 in self.callbacks,
-                        'Could not register signal in local component.')
+                        'Could not register signal in local client.')
         self.assertTrue(2 in self.callbacks,
-                        'Could not register signal in local component.')
+                        'Could not register signal in local client.')
 
     def test_register_signal_replace(self):
         """
-        Make sure components can replace already registered callbacks.
+        Make sure clients can replace already registered callbacks.
         """
         sig = 3
         cbk = lambda x: True
@@ -120,21 +123,32 @@ 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):
         """
-        Ensure the server can register components to be signaled.
+        Ensure the server can register clients to be signaled.
         """
         sig = 5
         request = RegisterRequest()
@@ -143,42 +157,39 @@ class EventsTestCase(unittest.TestCase):
         request.mac_method = mac_auth.MacMethod.MAC_NONE
         request.mac = ""
         service = RpcService(EventsServerService_Stub, port, 'localhost')
-        complist = server.registered_components
+        complist = server.registered_clients
         self.assertEqual({}, complist,
                          'There should be no registered_ports when '
                          'server has just been created.')
         response = service.register(request, timeout=1000)
         self.assertTrue(sig in complist, "Signal not registered succesfully.")
         self.assertTrue(8091 in complist[sig],
-                        'Failed registering component port.')
+                        'Failed registering client port.')
 
-    def test_component_request_register(self):
+    def test_client_request_register(self):
         """
-        Ensure components can register themselves with server.
+        Ensure clients can register themselves with server.
         """
         sig = 6
-        complist = server.registered_components
+        complist = server.registered_clients
         self.assertTrue(sig not in complist,
-                        'There should be no registered components for this '
+                        'There should be no registered clients for this '
                         'signal.')
         events.register(sig, lambda x: True)
         time.sleep(0.1)
-        port = component.EventsComponentDaemon.get_instance().get_port()
-        self.assertTrue(sig in complist, 'Failed registering component.')
+        port = client.EventsClientDaemon.get_instance().get_port()
+        self.assertTrue(sig in complist, 'Failed registering client.')
         self.assertTrue(port in complist[sig],
-                        'Failed registering component port.')
+                        'Failed registering client port.')
 
-    def test_component_receives_signal(self):
+    def test_client_receives_signal(self):
         """
-        Ensure components can receive signals.
+        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 = ""
@@ -188,46 +199,230 @@ 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_component_send_signal(self):
+    def test_client_send_signal(self):
         """
-        Ensure components can send signals.
+        Ensure clients can send signals.
         """
         sig = 8
         response = events.signal(sig)
         self.assertTrue(response.status == response.OK,
                         'Received wrong response status when signaling.')
 
-    def test_component_unregister_all(self):
+    def test_client_unregister_all(self):
         """
-        Test that the component can unregister all events for one signal.
+        Test that the client can unregister all events for one signal.
         """
         sig = CLIENT_UID
-        complist = server.registered_components
+        complist = server.registered_clients
         events.register(sig, lambda x: True)
         events.register(sig, lambda x: True)
         time.sleep(0.1)
         events.unregister(sig)
         time.sleep(0.1)
-        port = component.EventsComponentDaemon.get_instance().get_port()
+        port = client.EventsClientDaemon.get_instance().get_port()
         self.assertFalse(bool(complist[sig]))
         self.assertTrue(port not in complist[sig])
 
-    def test_component_unregister_by_uid(self):
+    def test_client_unregister_by_uid(self):
         """
-        Test that the component can unregister an event by uid.
+        Test that the client can unregister an event by uid.
         """
         sig = CLIENT_UID
-        complist = server.registered_components
+        complist = server.registered_clients
         events.register(sig, lambda x: True, uid='cbkuid')
         events.register(sig, lambda x: True, uid='cbkuid2')
         time.sleep(0.1)
         events.unregister(sig, uid='cbkuid')
         time.sleep(0.1)
-        port = component.EventsComponentDaemon.get_instance().get_port()
+        port = client.EventsClientDaemon.get_instance().get_port()
         self.assertTrue(sig in complist)
         self.assertTrue(len(complist[sig]) == 1)
         self.assertTrue(
-            component.registered_callbacks[sig].pop()[0] == 'cbkuid2')
+            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)
+
+    def test_async_register(self):
+        """
+        Test asynchronous registering of callbacks.
+        """
+        flag = Mock()
+
+        # executed after async register, when response is received from server
+        def reqcbk(request, response):
+            flag(request.event)
+
+        # callback registered by application
+        def callback(request):
+            pass
+
+        # passing a callback as reqcbk param makes the call asynchronous
+        result = events.register(CLIENT_UID, callback, reqcbk=reqcbk)
+        self.assertIsNone(result)
+        events.signal(CLIENT_UID)
+        time.sleep(1)  # wait for signal to arrive from server
+        flag.assert_called_once_with(CLIENT_UID)
+
+    def test_async_signal(self):
+        """
+        Test asynchronous registering of callbacks.
+        """
+        flag = Mock()
+
+        # executed after async signal, when response is received from server
+        def reqcbk(request, response):
+            flag(request.event)
+
+        # passing a callback as reqcbk param makes the call asynchronous
+        result = events.signal(CLIENT_UID, reqcbk=reqcbk)
+        self.assertIsNone(result)
+        time.sleep(1)  # wait for signal to arrive from server
+        flag.assert_called_once_with(CLIENT_UID)
+
+    def test_async_unregister(self):
+        """
+        Test asynchronous unregistering of callbacks.
+        """
+        flag = Mock()
+
+        # executed after async signal, when response is received from server
+        def reqcbk(request, response):
+            flag(request.event)
+
+        # callback registered by application
+        def callback(request):
+            pass
+
+        # passing a callback as reqcbk param makes the call asynchronous
+        events.register(CLIENT_UID, callback)
+        result = events.unregister(CLIENT_UID, reqcbk=reqcbk)
+        self.assertIsNone(result)
+        time.sleep(1)  # wait for signal to arrive from server
+        flag.assert_called_once_with(CLIENT_UID)
+
+    def test_async_ping_server(self):
+        """
+        Test asynchronous pinging of server.
+        """
+        flag = Mock()
+
+        # executed after async signal, when response is received from server
+        def reqcbk(request, response):
+            flag()
+
+        result = events.ping_server(reqcbk=reqcbk)
+        self.assertIsNone(result)
+        time.sleep(1)  # wait for response to arrive from server.
+        flag.assert_called_once_with()
+
+    def test_async_ping_client(self):
+        """
+        Test asynchronous pinging of client.
+        """
+        flag = Mock()
+
+        # executed after async signal, when response is received from server
+        def reqcbk(request, response):
+            flag()
+
+        daemon = client.ensure_client_daemon()
+        result = events.ping_client(daemon.get_port(), reqcbk=reqcbk)
+        self.assertIsNone(result)
+        time.sleep(1)  # wait for response to arrive from server.
+        flag.assert_called_once_with()