An Error Occurred in e4mc | Quick Fixes

The “An error occurred in e4mc” message means something went wrong when the e4mc relay server tried to connect your LAN game to the public internet.

Based on common causes and official reports, here are the most effective ways to fix it:

🧭 Key Causes

1. Relay server issues

   • e4mc relies on cloud relay servers (e.g., NA/EU). If they’re down, overloaded, or timing out, you’ll get this error—even if your client appears to run normally.

2. Mod or version conflicts

   • Mods like Sodium, Lithium, C2ME, or mismatched Fabric API/Minecraft versions can disrupt the relay handshake.

3. QUIC protocol handshake fails

   • Errors deep in Netty’s QUIC handler often cause disconnects immediately after attempting connection.

4. Offline/cracked Minecraft launchers

   • Not using an authenticated launcher can silently block the relay from establishing a valid session.

✅ Quick Fixes

1. Check Relay status & region

• Go to: status.e4mc.link (if available)

• Try forcing e4mc.relay.region=eu in your config/e4mc.toml—EU relays are often more stable.

2. Minimize mods

Run only:

• Fabric Loader

• Fabric API

• e4mc (matched version)

Remove or disable any added mods like Sodium, Lithium, etc., during testing.

3. Update Java & Launcher

• Use Java 17

• Allocate sufficient memory (e.g., -Xmx4G -Xms2G)

• Use an authenticated launcher like official Minecraft Launcher or PrismLauncher with valid credentials.

4. Test network configuration

• Turn off firewall/antivirus for javaw.exe

• Switch networks (e.g., use a mobile hotspot)

• Avoid VPNs or heavy NAT setups.

5. Check logs & report feedback

If the error persists, gather:

• logs/latest.log showing the error trace

• Config details (e4mc version, Fabric, mods, Java, Minecraft version)

• Submit an issue on the GitHub/Gitea repo: provide logs and context.

Also Read : Destiny 2 Weasel Error Code | Quick Fixes to Try First

🧠 Developer Insights

• The error typically occurs deep in the QUIC layer (QuicheQuicChannel.failPendingConnectPromise) due to silent handshake timeouts or relay failures.

• Community builds have resolved similar issues by switching to nightly builds of e4mc and Fabric when stable releases lag behind relay protocol changes.

🔧 Summary Table

🚀 Summary

This error stems from a failed QUIC handshake with the relay, often due to server-side issues or local conflicts. The best approach is to simplify your setup, test alternative relays or networks, and update your environment. If problems persist, report complete logs to the developers for further help.