java.net.SocketException: Connection reset

What the log looks like

java\.net\.SocketException: Connection reset
Exception occurred in netty pipeline[\r\n]+java\.net\.SocketException: Connection reset

How to fix it

1. If you see this in a server console right when a player disconnects, check that player's client `crash-reports` folder or `latest.log`—a client-side mod crash forces the socket closed and makes the server log `Connection reset` as a symptom.
2. Allow both your Minecraft launcher and the exact Java executable it uses (`javaw.exe` and `java.exe` inside your launcher's runtime folder) through Windows Defender Firewall for both Private and Public networks.
3. Temporarily disable VPNs, system proxies, or antivirus HTTPS/web-shield scanning if your launcher freezes or fails while checking for updates or contacting `localhost` authentication services.
4. Change your system DNS to `1.1.1.1` (Cloudflare) or `8.8.8.8` (Google), then open Command Prompt as Administrator and run `ipconfig /flushdns` followed by `netsh winsock reset`, and restart your PC.
5. If only modded multiplayer disconnects with this error, ensure your client mod list and versions match the server exactly and install a packet-timeout helper mod or ask the host to check for oversized packets.

Check your own log