Activist group Great Firewall Report spotted the outage, which it said disrupted all traffic to TCP port 443 – the standard port used for carrying HTTPS traffic.
“Between approximately 00:34 and 01:48 (Beijing Time, UTC+8) on August 20, 2025, the Great Firewall of China (GFW) exhibited anomalous behavior by unconditionally injecting forged TCP RST+ACK packets to disrupt all connections on TCP port 443,” the group wrote in a Wednesday post.
That disruption meant Chinese netizens couldn’t reach most websites hosted outside China, which is inconvenient. The incident also blocked other services that rely on port 443, which could be more problematic because many services need to communicate with servers or sources of information outside China for operational reasons. For example, Apple and Tesla use the port to connect to offshore servers that power some of their basic services.
Yeah technically anything can run on any ports, we just like to default certain things.
Ssh for example can work on port 2000 or whatever. Port knocking is fun too.
Oh, it’s not even that some other protocol is operating on 443. It’s that the underlying transport is HTTPS, just for something that’s not a website rendered in a browser by the client. Microsoft, for example, used RPC over HTTPS for Outlook connectivity to Exchange for a hot minute.
Ah gotcha. In this case yeah.