diff --git a/socketio/asyncio_server.py b/socketio/asyncio_server.py
index 8162452..27e1ad1 100644
--- a/socketio/asyncio_server.py
+++ b/socketio/asyncio_server.py
@@ -428,6 +428,10 @@ class AsyncServer(server.Server):
         namespace = namespace or '/'
         self.logger.info('received event "%s" from %s [%s]', data[0], sid,
                          namespace)
+        if not self.manager.is_connected(sid, namespace):
+            self.logger.warning('%s is not connected to namespace %s',
+                                sid, namespace)
+            return
         if self.async_handlers:
             self.start_background_task(self._handle_event_internal, self, sid,
                                        data, namespace, id)
diff --git a/socketio/server.py b/socketio/server.py
index 2ddd94c..3cae39f 100644
--- a/socketio/server.py
+++ b/socketio/server.py
@@ -638,6 +638,10 @@ class Server(object):
         namespace = namespace or '/'
         self.logger.info('received event "%s" from %s [%s]', data[0], sid,
                          namespace)
+        if not self.manager.is_connected(sid, namespace):
+            self.logger.warning('%s is not connected to namespace %s',
+                                sid, namespace)
+            return
         if self.async_handlers:
             self.start_background_task(self._handle_event_internal, self, sid,
                                        data, namespace, id)
diff --git a/tests/asyncio/test_asyncio_server.py b/tests/asyncio/test_asyncio_server.py
index 02e13ec..8d0b2e0 100644
--- a/tests/asyncio/test_asyncio_server.py
+++ b/tests/asyncio/test_asyncio_server.py
@@ -436,6 +436,7 @@ class TestAsyncServer(unittest.TestCase):
     def test_handle_event(self, eio):
         eio.return_value.send = AsyncMock()
         s = asyncio_server.AsyncServer(async_handlers=False)
+        s.manager.connect('123', '/')
         handler = AsyncMock()
         s.on('my message', handler)
         _run(s._handle_eio_message('123', '2["my message","a","b","c"]'))
@@ -444,14 +445,25 @@ class TestAsyncServer(unittest.TestCase):
     def test_handle_event_with_namespace(self, eio):
         eio.return_value.send = AsyncMock()
         s = asyncio_server.AsyncServer(async_handlers=False)
+        s.manager.connect('123', '/foo')
         handler = mock.MagicMock()
         s.on('my message', handler, namespace='/foo')
         _run(s._handle_eio_message('123', '2/foo,["my message","a","b","c"]'))
         handler.assert_called_once_with('123', 'a', 'b', 'c')
 
+    def test_handle_event_with_disconnected_namespace(self, eio):
+        eio.return_value.send = AsyncMock()
+        s = asyncio_server.AsyncServer(async_handlers=False)
+        s.manager.connect('123', '/foo')
+        handler = mock.MagicMock()
+        s.on('my message', handler, namespace='/bar')
+        _run(s._handle_eio_message('123', '2/bar,["my message","a","b","c"]'))
+        handler.assert_not_called()
+
     def test_handle_event_binary(self, eio):
         eio.return_value.send = AsyncMock()
         s = asyncio_server.AsyncServer(async_handlers=False)
+        s.manager.connect('123', '/')
         handler = mock.MagicMock()
         s.on('my message', handler)
         _run(s._handle_eio_message('123', '52-["my message","a",'
@@ -476,6 +488,7 @@ class TestAsyncServer(unittest.TestCase):
     def test_handle_event_with_ack(self, eio):
         eio.return_value.send = AsyncMock()
         s = asyncio_server.AsyncServer(async_handlers=False)
+        s.manager.connect('123', '/')
         handler = mock.MagicMock(return_value='foo')
         s.on('my message', handler)
         _run(s._handle_eio_message('123', '21000["my message","foo"]'))
@@ -486,6 +499,7 @@ class TestAsyncServer(unittest.TestCase):
     def test_handle_event_with_ack_none(self, eio):
         eio.return_value.send = AsyncMock()
         s = asyncio_server.AsyncServer(async_handlers=False)
+        s.manager.connect('123', '/')
         handler = mock.MagicMock(return_value=None)
         s.on('my message', handler)
         _run(s._handle_eio_message('123', '21000["my message","foo"]'))
@@ -729,6 +743,7 @@ class TestAsyncServer(unittest.TestCase):
 
     def test_async_handlers(self, eio):
         s = asyncio_server.AsyncServer(async_handlers=True)
+        s.manager.connect('123', '/')
         _run(s._handle_eio_message('123', '2["my message","a","b","c"]'))
         s.eio.start_background_task.assert_called_once_with(
             s._handle_event_internal, s, '123', ['my message', 'a', 'b', 'c'],
diff --git a/tests/common/test_server.py b/tests/common/test_server.py
index 667a465..3c4dbc2 100644
--- a/tests/common/test_server.py
+++ b/tests/common/test_server.py
@@ -392,6 +392,7 @@ class TestServer(unittest.TestCase):
 
     def test_handle_event(self, eio):
         s = server.Server(async_handlers=False)
+        s.manager.connect('123', '/')
         handler = mock.MagicMock()
         s.on('my message', handler)
         s._handle_eio_message('123', '2["my message","a","b","c"]')
@@ -399,13 +400,23 @@ class TestServer(unittest.TestCase):
 
     def test_handle_event_with_namespace(self, eio):
         s = server.Server(async_handlers=False)
+        s.manager.connect('123', '/foo')
         handler = mock.MagicMock()
         s.on('my message', handler, namespace='/foo')
         s._handle_eio_message('123', '2/foo,["my message","a","b","c"]')
         handler.assert_called_once_with('123', 'a', 'b', 'c')
 
+    def test_handle_event_with_disconnected_namespace(self, eio):
+        s = server.Server(async_handlers=False)
+        s.manager.connect('123', '/foo')
+        handler = mock.MagicMock()
+        s.on('my message', handler, namespace='/bar')
+        s._handle_eio_message('123', '2/bar,["my message","a","b","c"]')
+        handler.assert_not_called()
+
     def test_handle_event_binary(self, eio):
         s = server.Server(async_handlers=False)
+        s.manager.connect('123', '/')
         handler = mock.MagicMock()
         s.on('my message', handler)
         s._handle_eio_message('123', '52-["my message","a",'
@@ -418,7 +429,6 @@ class TestServer(unittest.TestCase):
     def test_handle_event_binary_ack(self, eio):
         mgr = mock.MagicMock()
         s = server.Server(client_manager=mgr)
-        s.manager.initialize(s)
         s._handle_eio_message('123', '61-321["my message","a",'
                                      '{"_placeholder":true,"num":0}]')
         s._handle_eio_message('123', b'foo')
@@ -427,6 +437,7 @@ class TestServer(unittest.TestCase):
 
     def test_handle_event_with_ack(self, eio):
         s = server.Server(async_handlers=False)
+        s.manager.connect('123', '/')
         handler = mock.MagicMock(return_value='foo')
         s.on('my message', handler)
         s._handle_eio_message('123', '21000["my message","foo"]')
@@ -436,6 +447,7 @@ class TestServer(unittest.TestCase):
 
     def test_handle_event_with_ack_none(self, eio):
         s = server.Server(async_handlers=False)
+        s.manager.connect('123', '/')
         handler = mock.MagicMock(return_value=None)
         s.on('my message', handler)
         s._handle_eio_message('123', '21000["my message","foo"]')
@@ -655,6 +667,7 @@ class TestServer(unittest.TestCase):
 
     def test_async_handlers(self, eio):
         s = server.Server(async_handlers=True)
+        s.manager.connect('123', '/')
         s._handle_eio_message('123', '2["my message","a","b","c"]')
         s.eio.start_background_task.assert_called_once_with(
             s._handle_event_internal, s, '123', ['my message', 'a', 'b', 'c'],