Retry refused adapter callback connections

src/debugpy/adapter/__main__.py

@@ -82,11 +82,9 @@ def main():
         )
 
         try:
-            ipv6 = localhost.count(":") > 1
-            sock = sockets.create_client(ipv6)
+            sock = sockets.connect((localhost, args.for_server), 5, 0.1)
             try:
                 sock.settimeout(None)
-                sock.connect((localhost, args.for_server))
                 sock_io = sock.makefile("wb", 0)
                 try:
                     sock_io.write(json.dumps(endpoints).encode("utf-8"))

src/debugpy/common/sockets.py

@@ -5,6 +5,7 @@
 import socket
 import sys
 import threading
+import time
 from typing import Any, Callable, Union
 
 from debugpy.common import log
@@ -99,6 +100,28 @@ def create_client(ipv6=False):
     return _new_sock(ipv6)
 
 
+def connect(
+    address: tuple[str, int], attempts: int = 1, retry_interval: float = 0
+) -> socket.socket:
+    """Return a client socket connected to the given address."""
+    assert attempts > 0
+    ipv6 = address[0].count(":") > 1
+    while True:
+        sock = create_client(ipv6)
+        try:
+            sock.connect(address)
+            return sock
+        except ConnectionRefusedError:
+            close_socket(sock)
+            attempts -= 1
+            if attempts == 0:
+                raise
+            time.sleep(retry_interval)
+        except Exception:
+            close_socket(sock)
+            raise
+
+
 def _new_sock(ipv6=False):
     address_family = socket.AF_INET6 if ipv6 else socket.AF_INET
     sock = socket.socket(address_family, socket.SOCK_STREAM, socket.IPPROTO_TCP)

tests/debugpy/common/test_socket.py

@@ -8,6 +8,28 @@
 from debugpy.common import sockets
 
 
+def test_connect_retries_connection_refused(monkeypatch):
+    class Client:
+        def __init__(self, refused=False):
+            self.refused = refused
+            self.closed = False
+
+        def connect(self, address):
+            if self.refused:
+                raise ConnectionRefusedError
+
+        def close(self):
+            self.closed = True
+
+    refused_client = Client(refused=True)
+    connected_client = Client()
+    clients = [refused_client, connected_client]
+    monkeypatch.setattr(sockets, "create_client", lambda ipv6: clients.pop(0))
+    connected = sockets.connect(("127.0.0.1", 5678), attempts=2)
+    assert connected is connected_client
+    assert refused_client.closed is True
+
+
 class TestSocketServerReuse(object):
     HOST1 = "127.0.0.1"
     # NOTE: Windows allows loopback range 127/8. Some flavors of Linux support