Merge a4342e9aa1 into b7ba504e06

subclasses (ConnectionResetError, BrokenPipeError). When a client
  becomes unreachable mid-generation (laptop sleeps, drops off WiFi),
  the OS raises OSError: [Errno 113] No route to host (EHOSTUNREACH),
  which is a sibling of ConnectionError, not a subclass. It therefore
  escaped the handler, propagated through publish_loop, and could crash
  the entire server over a single dead client.

server.py

@@ -72,7 +72,7 @@ def _remove_sensitive_from_queue(queue: list) -> list:
 async def send_socket_catch_exception(function, message):
     try:
         await function(message)
-    except (aiohttp.ClientError, aiohttp.ClientPayloadError, ConnectionResetError, BrokenPipeError, ConnectionError) as err:
+    except (aiohttp.ClientError, aiohttp.ClientPayloadError, OSError) as err:
         logging.warning("send error: {}".format(err))
 
 # Track deprecated paths that have been warned about to only warn once per file

tests-unit/server_test/test_send_socket_catch_exception.py

@@ -0,0 +1,38 @@
+"""Tests for server.send_socket_catch_exception.
+"""
+
+import pytest
+import utils.install_util  # noqa: F401
+from server import send_socket_catch_exception
+
+pytestmark = pytest.mark.asyncio
+
+
+class TestSendSocketCatchException:
+    """The send helper must swallow client-disconnect errors, never propagate them."""
+
+    async def test_swallows_no_route_to_host(self, caplog):
+
+        async def failing_send(_message):
+            raise OSError(113, "No route to host")
+
+        await send_socket_catch_exception(failing_send, b"payload")
+        assert "send error" in caplog.text
+
+    async def test_swallows_connection_reset(self):
+        """Existing behaviour preserved: ConnectionResetError is still caught."""
+
+        async def failing_send(_message):
+            raise ConnectionResetError("peer reset the connection")
+
+        await send_socket_catch_exception(failing_send, b"payload")
+
+    async def test_successful_send_delivers_message(self):
+        """When the send succeeds the message is passed through and nothing is logged."""
+        received = []
+
+        async def ok_send(message):
+            received.append(message)
+
+        await send_socket_catch_exception(ok_send, b"hello")
+        assert received == [b"hello"]