A friend contacted me in a hurry because publishing posts in the WordPress admin area kept returning Error 324 ERR_EMPTY_RESPONSE. The site was part of a WordPress multisite setup, and at first glance there were no signs of a hack or of corrupted site data.
The strange part was that the issue appeared after the local computer’s IP settings were changed. That sounded unrelated at first, but it was enough to suggest that the problem might not be in WordPress itself.
I went through the usual checks one by one:
- Enabled WordPress debug mode. Only a minor warning appeared, nothing that should block publishing.
- Disabled all plugins. The error still happened, so it was probably not caused by a plugin.
- Reinstalled WordPress core files. The problem remained.
- Checked the database. It looked normal.
After those tests, it became much more likely that the problem was happening at the network layer. The server response may have been blocked or dropped before it reached the browser. That led us to check the firewall rules configured on the server.
Once the firewall was disabled temporarily, publishing worked normally again. That confirmed the root cause: the firewall was interfering with the response sent back when WordPress tried to publish the post.
If you run into the same ERR_EMPTY_RESPONSE problem, it is worth checking firewall rules and server networking before spending too much time debugging WordPress code. If you cannot access the server directly, copy the site to a local environment and test there. If the issue disappears locally, the server environment is the most likely cause.
