Bug report

Windows: remote pdb loses its interrupt connection after about 120 seconds

Tested on Windows 11 x64 (build 26100), CPython 3.16.0a1+dev,
main commit 7b12a415c85d88eeb22a806b2bc9472d471b8e60, Release/MSVC build.

Remote debugging initially works, but its Windows interrupt channel fails after
about two minutes.

Use this target script:

import os
import time

print(os.getpid(), flush=True)
while True:
    time.sleep(0.1)

1. Run the target with the newly built interpreter
2. Attach from another terminal using the same build typing python -m pdb -p <PID>
3. Enter c, wait 135 seconds, then interrupt from the debugger client (Ctrl+C)

The expected result should be the target stopping and another debugger prompt appearing.

But in this case the target's listener thread fails in sock.recv(1024) with
ConnectionResetError: [WinError 10054]. Forwarding the subsequent client
interrupt fails in self.interrupt_sock.sendall(...) with
ConnectionAbortedError: [WinError 10053]. The target application keeps running.

Confirmed in two automated real pdb.attach() / sys.remote_exec() sessions,
raising SIGINT in the client after 135 seconds. Removing only
sock.shutdown(socket.SHUT_WR) from _PdbServer._start_signal_listener() in
memory made both control runs succeed, including variable evaluation and
detach after the interrupt.

The regular test_remote_pdb still passes (47 passed, 2 skipped), since
its interrupt test does not wait for this tested 120 second idle interval.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Windows