diff --git a/ipykernel/debugger.py b/ipykernel/debugger.py
index 900c10bf0..8acb65cbf 100644
--- a/ipykernel/debugger.py
+++ b/ipykernel/debugger.py
@@ -10,6 +10,7 @@
 from .compiler import (get_file_name, get_tmp_directory, get_tmp_hash_seed)
 
 import debugpy
+import time
 
 class DebugpyMessageQueue:
 
@@ -96,13 +97,19 @@ class DebugpyClient:
     def __init__(self, log, debugpy_stream, event_callback):
         self.log = log
         self.debugpy_stream = debugpy_stream
-        self.routing_id = None
         self.event_callback = event_callback
         self.message_queue = DebugpyMessageQueue(self._forward_event, self.log)
+        self.debugpy_host = '127.0.0.1'
+        self.debugpy_port = -1
+        self.routing_id = None
         self.wait_for_attach = True
         self.init_event = Event()
         self.init_event_seq = -1
 
+    def _get_endpoint(self):
+        host, port = self.get_host_port()
+        return 'tcp://' + host + ':' + str(port)
+
     def _forward_event(self, msg):
         if msg['event'] == 'initialized':
             self.init_event.set()
@@ -146,6 +153,28 @@ async def _handle_init_sequence(self):
         attach_rep = await self._wait_for_response()
         return attach_rep
 
+    def get_host_port(self):
+        if self.debugpy_port == -1:
+            socket = self.debugpy_stream.socket
+            socket.bind_to_random_port('tcp://' + self.debugpy_host)
+            self.endpoint = socket.getsockopt(zmq.LAST_ENDPOINT).decode('utf-8')
+            socket.unbind(self.endpoint)
+            index = self.endpoint.rfind(':')
+            self.debugpy_port = self.endpoint[index+1:]
+        return self.debugpy_host, self.debugpy_port
+
+
+    def connect_tcp_socket(self):
+        self.debugpy_stream.socket.connect(self._get_endpoint())
+        self.routing_id = self.debugpy_stream.socket.getsockopt(zmq.ROUTING_ID)
+
+    def disconnect_tcp_socket(self):
+        self.debugpy_stream.socket.disconnect(self._get_endpoint())
+        self.routing_id = None
+        self.init_event = Event()
+        self.init_event_seq = -1
+        self.wait_for_attach = True
+
     def receive_dap_frame(self, frame):
         self.message_queue.put_tcp_frame(frame)
 
@@ -194,8 +223,11 @@ def __init__(self, log, debugpy_stream, event_callback, shell_socket, session):
         self.breakpoint_list = {}
         self.stopped_threads = []
 
+        self.debugpy_initialized = False
+
         self.debugpy_host = '127.0.0.1'
         self.debugpy_port = 0
+        self.endpoint = None
 
     async def _forward_message(self, msg):
         return await self.debugpy_client.send_dap_request(msg)
@@ -205,29 +237,24 @@ def tcp_client(self):
         return self.debugpy_client
 
     def start(self):
-        socket = self.debugpy_client.debugpy_stream.socket
-        socket.bind_to_random_port('tcp://' + self.debugpy_host)
-        endpoint = socket.getsockopt(zmq.LAST_ENDPOINT).decode('utf-8')
-        socket.unbind(endpoint)
-        index = endpoint.rfind(':')
-        self.debugpy_port = endpoint[index+1:]
-        code = 'import debugpy;'
-        code += 'debugpy.listen(("' + self.debugpy_host + '",' + self.debugpy_port + '))'
-        content = {
-            'code': code,
-            'silent': True
-        }
-        self.session.send(self.shell_socket, 'execute_request', content,
-                          None, (self.shell_socket.getsockopt(zmq.ROUTING_ID)))
+        if not self.debugpy_initialized:
+            host, port = self.debugpy_client.get_host_port()
+            code = 'import debugpy;'
+            code += 'debugpy.listen(("' + host + '",' + port + '))'
+            content = {
+                'code': code,
+                'silent': True
+            }
+            self.session.send(self.shell_socket, 'execute_request', content,
+                              None, (self.shell_socket.getsockopt(zmq.ROUTING_ID)))
                           
-        self.session.recv(self.shell_socket, mode=0)
-        socket.connect(endpoint)
-        debugpy.trace_this_thread(False)
-        return True
+            ident, msg = self.session.recv(self.shell_socket, mode=0)
+            self.debugpy_initialized = msg['content']['status'] == 'ok'
+        self.debugpy_client.connect_tcp_socket()
+        return self.debugpy_initialized
 
     def stop(self):
-        # TODO 
-        pass
+        self.debugpy_client.disconnect_tcp_socket()
 
     async def dumpCell(self, message):
         code = message['arguments']['code']
@@ -289,9 +316,10 @@ async def variables(self, message):
         return reply
 
     async def attach(self, message):
+        host, port = self.debugpy_client.get_host_port()
         message['arguments']['connect'] = {
-            'host': self.debugpy_host,
-            'port': self.debugpy_port
+            'host': host,
+            'port': port
         }
         message['arguments']['logToFile'] = True
         return await self._forward_message(message)