Fix UDP server hanging on SIGINT due to untracked background tasks

[Copilot]

UDP server would not terminate with Ctrl+C because asyncio.create_task() calls in the datagram handler created untracked tasks that prevented clean shutdown.

Changes

• Track background tasks: Added background_tasks set to UDPInputServer with automatic cleanup via task completion callback
• Enhanced shutdown: stop() now cancels pending tasks, waits for completion, and allows transport flush time before closing

# Before: fire-and-forget task creation
def datagram_received(self, data: bytes, addr: tuple):
    asyncio.create_task(self.server.handle_packet(data, addr))

# After: tracked with automatic cleanup
def datagram_received(self, data: bytes, addr: tuple):
    task = asyncio.create_task(self.server.handle_packet(data, addr))
    self.server.background_tasks.add(task)
    task.add_done_callback(lambda t: self.server.background_tasks.discard(t))

# Enhanced stop() method
async def stop(self):
    self.running = False
    
    # Cancel and wait for background tasks
    for task in self.background_tasks:
        task.cancel()
    if self.background_tasks:
        await asyncio.gather(*self.background_tasks, return_exceptions=True)
    
    # Close transport with flush time
    if self.transport:
        self.transport.close()
        await asyncio.sleep(0.1)
        self.transport = None

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• astral.sh
  • Triggering command: /usr/bin/curl curl -LsSf REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

I can not finish the udp server with ctrl-c

Created from VS Code via the GitHub Pull Request extension.

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[shugonta]

@copilot How did you change udp_server.py

[Copilot]

@copilot How did you change udp_server.py

I made three changes to server/udp_server.py:

1. Line 100 - Added background_tasks set to track async tasks:

   self.background_tasks: Set[asyncio.Task] = set()

2. Lines 54-56 - Modified datagram_received() to track tasks and auto-cleanup:

   task = asyncio.create_task(self.server.handle_packet(data, addr))
   self.server.background_tasks.add(task)
   task.add_done_callback(lambda t: self.server.background_tasks.discard(t))

3. Lines 142-149 - Enhanced stop() to cancel tasks before closing:

   # Cancel all background tasks
   for task in self.background_tasks:
       task.cancel()
   
   # Wait for all background tasks to complete
   if self.background_tasks:
       await asyncio.gather(*self.background_tasks, return_exceptions=True)
   
   # Close transport with 0.1s flush time

These changes ensure background tasks don't prevent clean shutdown when Ctrl+C is pressed.