The issue arises when the user tries to join or connect a server but encounters the following message: “Connection Lost Internal Exception: java.io.IOException: An existing connection was forcibly closed by the remote host” Before proceeding with the solutions to stop internal exceptions in Java IO IOException, check if trying another network cable (if using an ethernet connection) resolves the issue. If you have a long username (7+ characters), then check if reducing it to (7 or fewer characters) solves the issue. Also, check if your internet speed meets the minimum speed requirements of Minecraft. Moreover, make sure to log out/disconnect the Minechat (if using) and then close it. Additionally, check if launching the Minecraft launcher (or server) as an administrator resolves the issue.
Solution 1: Update the Minecraft Launcher to the Latest Build
You may encounter the internal exception issue if the Minecraft launcher of your system is outdated as it can create incompatibility between the launcher & server. In this context, updating the Minecraft launcher to the latest release may solve the problem. But before moving on, check if you have more than one account configured with the Minecraft launcher, if so, then remove all the other accounts but one.
Solution 2: Clear the DNS Cache of Your System
The Java.io error may emerge if the DNS cache of your system is corrupt as it may lead to the system’s ability to resolve the domain name. In this context, flushing the DNS cache (which will force the system to re-fetch the combinations) may solve the problem. If the issue persists, then check if changing DNS server (e.g., Google DNS) resolves the internal exception issue.
Solution 3: Disable Server’s Resource Pack
Resource packs allow the players to do a lot of customization (like textures, music, models, splash tests, etc.) but this customization may hinder the client/server communication and thus cause the IOexception issue. In this scenario, disabling the server’s resource pack may solve the problem.
Solution 4: Uninstall the Conflicting Applications
You may encounter the Java.io issue if an application on your system is hindering the operation of Minecraft. In this scenario, removing the conflicting application may solve the problem. You can clean boot your PC to find out the problematic application. For illustration, we will discuss the process for the Hamachi VPN (reported by the users to cause the issue).
Solution 5: Decrease the Render Distance in the Minecraft Settings
The internal exception issue may arise if Minecraft could not render all the video blocks at once (due to the poor internet speed). In this context, decreasing the Render Distance in the Minecraft settings to the lowest possible may solve the problem.
Solution 6: Edit the Java Settings
The Java.io error may arise if the Java installation of your system is not properly configured. In this context, editing the Java settings (like enabling the Native Sandbox) may solve the problem. But before proceeding, make sure you have only one Java installation.
Update Java to the Latest Build
Enable Native Sandbox
Edit the Java Path in the Launcher Settings
If the issue persists, then check if reinstalling Java sorts out the IOexception issue.
Solution 7: Repair / Reinstall the Minecraft
The Java.io issue may arise if the Minecraft installation is corrupt. In this context, repairing or reinstalling it may solve the problem.
Solution 8: Edit the Network-Related Settings
Minecraft may show the internal exception issue if the network settings of your system are not properly configured (or your ISP is blocking access to a resource essential for the operation of Minecraft). In this case, editing the network settings (or trying another network/VPN) may solve the problem.
Try Another Network or a VPN
Disable NAT Acceleration in the Router’s Settings
Solution 9: Edit the Firewall Settings
You may encounter the internal exception issue if the Firewall of your system is blocking access to a resource essential for the operation of Minecraft. In this context, editing the Firewall settings (like allowing Java (TM) Platform SE Binary in the Firewall settings) may solve the problem. Before proceeding, it will be a good idea to check if temporarily disabling the firewall of your system resolves the issue. For illustration, we will go through the process for the Windows Defender Firewall. Warning: Advance at your own risk as editing the firewall’s settings is a skillful task & if done wrong, you may expose your system/data to threats.
Set Java (TM) Platform SE to Private in the Firewall Settings
Allow the Minecraft Through the Firewall
If the issue persists, check if allowing the Minecraft connections through the router’s Firewall (if any) resolves the issue (especially, if it is using some autoblocking feature). If that did not do the trick, check if the parental controls are not restricting the Minecraft access. Also, it will be a good idea to ensure that the ports are properly forwarded in the system/router firewall as required by Minecraft. If the issue persists, check if allocating more RAM to Minecraft solves the problem. If that did not do the trick, you may contact the server’s admins to delete your player data or check for a server-side problem. If the issue did not resolve so far, you may have to perform a factory reset of your PC & if that did not do the trick, get your system (especially, hard disk and network/Wi-Fi card) checked for a hardware error.
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