{"id":"58c61ec4847764c2","repo":"aio-libs/aiohttp","slug":"connection-lost-58c61e","errorCode":null,"errorMessage":"Connection lost","messagePattern":"Connection lost","errorType":"exception","errorClass":"ConnectionResetError","httpStatus":null,"severity":"error","filePath":"aiohttp/web_ws.py","lineNumber":365,"sourceCode":"        return (\n            response_headers,\n            protocol,\n            compress,\n            notakeover,\n        )\n\n    def _pre_start(self, request: BaseRequest) -> tuple[str | None, WebSocketWriter]:\n        self._loop = request._loop\n\n        headers, protocol, compress, notakeover = self._handshake(request)\n\n        self.set_status(101)\n        self.headers.update(headers)\n        self.force_close()\n        self._compress = compress\n        transport = request._protocol.transport\n        if transport is None:\n            raise ConnectionResetError(\"Connection lost\")\n        writer = WebSocketWriter(\n            request._protocol,\n            transport,\n            compress=compress,\n            notakeover=notakeover,\n            limit=self._writer_limit,\n        )\n\n        return protocol, writer\n\n    def _post_start(\n        self, request: BaseRequest, protocol: str | None, writer: WebSocketWriter\n    ) -> None:\n        self._ws_protocol = protocol\n        self._writer = writer\n\n        self._reset_heartbeat()\n","sourceCodeStart":347,"sourceCodeEnd":383,"githubUrl":"https://github.com/aio-libs/aiohttp/blob/c0ef574e29109210e96e652771ae4e7b88615fa4/aiohttp/web_ws.py#L347-L383","documentation":"Error \"Connection lost\" thrown in aio-libs/aiohttp.","triggerScenarios":"Thrown at aiohttp/web_ws.py:365 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":[],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"analyzedSha":"c0ef574e29109210e96e652771ae4e7b88615fa4","analyzedAt":"2026-08-04T19:51:05.467Z","schemaVersion":2}