How to Fix “An Error Occurred in e4mc” in Minecraft: Full Troubleshooting Guide

e4mc (Easy 4 Minecraft) is a mod that allows users to share local Minecraft worlds across the internet via public LAN links. However, many players encountered error: “An error occurred in e4mc”, especially when opening their worlds to LAN. This issue stems from multiple possible causes from mod conflicts to network errors and this guide walks you through how to fix it.

Root Causes of the e4mc Error

1. Relay Server Connectivity Failures

The most common reason for the error lies with the e4mc relay servers:

• Regional Relay Downtime: Users report that North American relays have been down for weeks at times.
• Handshake Failures: During the QUIC protocol handshake, the connection to e4mc’s relay may fail silently.
• Geolocation Impact: Users from certain countries may struggle to connect depending on routing latency.

Example Log:

[20:07:51] [nioEventLoopGroup-2-1/INFO]: [CHAT] An error occurred in e4mc
[20:07:51] [nioEventLoopGroup-2-1/WARN]: An exception was thrown...
java.lang.RuntimeException: null
at link.e4mc.QuiclimeSession.lambda$start$4(QuiclimeSession.java:328)

2. Mod Conflicts and Compatibility Problems

Certain mods can interfere with e4mc’s operation:

• Performance Mods like Sodium, Lithium, C2ME
• Network-altering Mods such as NoChatReports
• Version mismatches between Fabric API, e4mc, and Minecraft core

These can disrupt how e4mc initializes relay connections or handles packets.

3. Broken QUIC Protocol Implementation

Errors deep in the network layer show problems with Netty’s QUIC implementation, often involving DefaultPromise or QuicheQuicChannel failures. These are mostly internal to the mod, but are important for debugging:

at io.netty.incubator.codec.quic.QuicheQuicChannel.failPendingConnectPromise
at io.netty.util.concurrent.DefaultPromise.setFailure(DefaultPromise.java:109)

4. Offline Mode and Authentication Failures

Using PrismLauncher or cracked Minecraft clients can trigger:

com.mojang.authlib.exceptions.InvalidCredentialsException: Status: 401

Without Mojang authentication, the relay setup might silently fail.

Read More: How to Fix Minecraft Error Code B-0010 on Nintendo Switch (Step-by-Step Guide)

How to Fix “An Error Occurred in e4mc”

Step 1: Check Server & Relay Status

• Visit: https://status.e4mc.link (if available)
• Try again during off-peak hours
• Switch relay manually (EU vs NA) if configurable

Step 2: Clean Mod Setup and Version Isolation

Run a clean Minecraft instance with only required mods:

KEEP:

• e4mc (latest, e.g., 5.3.1)
• Fabric Loader and API

REMOVE TEMPORARILY:

• NoChatReports
• Sodium, Lithium, C2ME
• EnhancedBlockEntities, ModernFix

Step 3: System and Network Adjustments

• Update Java to version 17
• Allocate JVM memory: -Xmx4G -Xms2G
• Temporarily disable firewalls/antivirus blocking javaw.exe
• Switch between WiFi and mobile hotspot to test connectivity
• Ensure NAT isn’t restricting outgoing connections

Step 4: Log Inspection and Reporting

If the error persists, capture and share:

• Full latest.log from start to crash
• Modlist with versions
• JVM and Fabric loader versions

Submit issues at: https://github.com/janrupf/e4mc/issues

Developer-Level Notes

The stack trace indicates the error occurs in QuiclimeSession.java during relay initialization. Likely causes include:

• Unhandled null values in the network chain
• Relay timeout not properly caught
• Silent QUIC disconnects that do not return a user-facing message

Potential long-term improvements:

• Better fallback logic
• Retry attempts with other relay regions
• Clearer in-game messages

Advanced Tips for Resolving e4mc Errors

1. Custom Relay Configuration

If you’re experiencing issues with regional servers (e.g., NA relays), manually switching to more stable ones can help:

e4mc.relay.region=eu

This setting can be added to the mod’s config file to force use of European relays, which are often less congested.

2. Curated Version Compatibility Matrix

Stability varies significantly depending on the combination of e4mc, Fabric API, and Java versions. Use the following verified combinations:

Avoid using bleeding-edge Fabric versions unless explicitly tested with e4mc.

3. Clean Mod Environment Setup

When updating or troubleshooting:

• Fully delete .minecraft/mods and config folders related to e4mc
• Reinstall only necessary dependencies (e.g., Fabric Loader, Fabric API)
• Avoid importing legacy or migrated config files, which may carry over corrupted states

4. Advanced Network Workarounds

If relay communication is persistently broken due to ISP, firewall, or DNS restrictions:

• Use ngrok: Tunnels your local server port through a public endpoint
• Playit.gg: Lightweight relay alternative with public links
• ZeroTier VPN: Virtual LAN emulator that works across NAT/firewall blocks

These tools can replicate or replace e4mc functionality during extended outages.

If e4mc relay issues continue for weeks:

• Use ngrok to tunnel your LAN port
• Try Playit.gg – offers free public relay tunnel support
• ZeroTier VPN – a lightweight LAN emulator

Conclusion

“An error occurred in e4mc” usually means something went wrong connecting to the relay server. It’s often due to mod conflicts, relay downtime, or broken network handling. By isolating mods, updating all components, and checking logs, most users can resolve it.

If not, try alternatives or submit logs to the developers so the open-source community can evolve and strengthen e4mc’s reliability.