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How to Fix Forge Server Crash When Specifying IP

Solution for Minecraft Forge server crash when specifying IP in server.properties. Learn the main causes and how to fix the configuration.

#game-server-configuration #minecraft-java-edition #minecraft-modding-platform #network-settings #server-crashes #server-ip-binding #server-troubleshooting

11/09/2025, 01:26 PM

Why does my Minecraft Forge server crash when specifying an IP in server.properties?

I downloaded a server for Minecraft version 1.20.19, and everything installed successfully. However, if I don’t specify an IP in the “server.properties” file, the server starts without any issues. As soon as I add an IP address, the server crashes.

I’ve already tried rebooting my computer and completely closing the server, but the problem persists.

Here’s the crash log:

---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 2025-10-13 19:46:20
Description: Exception in server tick loop

java.lang.IllegalStateException: Failed to initialize server
	at TRANSFORMER/minecraft@1.21.9/net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:725) ~[forge-1.21.9-59.0.5-server.jar!/:?]
	at TRANSFORMER/minecraft@1.21.9/net.minecraft.server.MinecraftServer.lambda$spin$2(MinecraftServer.java:284) ~[forge-1.21.9-59.0.5-server.jar!/:?]
	at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]
Transformer Audit:
  net.minecraft.server.MinecraftServer
    REASON: classloading
    PLUGIN: accesstransformer:BEFORE


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- System Details --
Details:
	Minecraft Version: 1.21.9
	Minecraft Version ID: 1.21.9
	Operating System: Windows 10 (amd64) version 10.0
	Java Version: 21.0.7, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode, sharing), Oracle Corporation
	Memory: 90193928 bytes (86 MiB) / 339738624 bytes (324 MiB) up to 4282384384 bytes (4084 MiB)
	CPUs: 8
	Processor Vendor: GenuineIntel
	Processor Name: Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz
	Identifier: Intel64 Family 6 Model 58 Stepping 9
	Microarchitecture: Ivy Bridge (Client)
	Frequency (GHz): 3.41
	Number of physical packages: 1
	Number of physical CPUs: 4
	Number of logical CPUs: 8
	Graphics card #0 name: NVIDIA GeForce GTX 1050 Ti
	Graphics card #0 vendor: NVIDIA
	Graphics card #0 VRAM (MiB): 4096.00
	Graphics card #0 deviceId: VideoController1
	Graphics card #0 versionInfo: 32.0.15.8129
	Memory slot #0 capacity (MiB): 8192.00
	Memory slot #0 clockSpeed (GHz): 1.60
	Memory slot #0 type: DDR3
	Memory slot #1 capacity (MiB): 8192.00
	Memory slot #1 clockSpeed (GHz): 1.60
	Memory slot #1 type: DDR3
	Virtual memory max (MiB): 21704.77
	Virtual memory used (MiB): 6461.89
	Swap memory total (MiB): 5376.00
	Swap memory used (MiB): 0.00
	Space in storage for jna.tmpdir (MiB): <path not set>
	Space in storage for org.lwjgl.system.SharedLibraryExtractPath (MiB): <path not set>
	Space in storage for io.netty.native.workdir (MiB): <path not set>
	Space in storage for java.io.tmpdir (MiB): available: 450275.28, total: 953751.00
	Space in storage for workdir (MiB): available: 450275.28, total: 953751.00
	JVM Flags: 0 total; 
	Debug Flags: 0 total; 
	Server Running: true
	Active Data Packs: vanilla, mod:forge (incompatible)
	Available Data Packs: minecart_improvements, mod:forge (incompatible), redstone_experiments, trade_rebalance, vanilla
	Enabled Feature Flags: minecraft:vanilla
	World Generation: Stable
	World Seed: 7337146887455192698
	Suppressed Exceptions: ~~NONE~~
	Is Modded: Definitely; Server brand changed to 'forge'
	Type: Dedicated Server (map_server.txt)
	ModLauncher: 10.2.4
	ModLauncher launch target: forge_server
	ModLauncher naming: mcp
	ModLauncher services: 
		/ slf4jfixer PLUGINSERVICE 
		/ runtimedistcleaner PLUGINSERVICE 
		/ runtime_enum_extender PLUGINSERVICE 
		/ capability_token_subclass PLUGINSERVICE 
		/ accesstransformer PLUGINSERVICE 
		/ mixin PLUGINSERVICE 
		/ fml TRANSFORMATIONSERVICE 
		/ forge TRANSFORMATIONSERVICE 
		/ mixin TRANSFORMATIONSERVICE 
	FML Language Providers: 
		lowcodefml@59
		minecraft@1.0
		javafml@59.0.5
	Mod List: 
		forge-1.21.9-59.0.5-server.jar                    |Minecraft                     |minecraft                     |1.21.9              |DONE      |Manifest: NOSIGNATURE
		forge-1.21.9-59.0.5-universal.jar                 |Forge                         |forge                         |59.0.5              |DONE      |Manifest: NOSIGNATURE
	Crash Report UUID: 47e820c1-b04c-460c-a7ed-fc6107e9cc4d
	FML: 59.0
	Forge: net.minecraftforge:59.0.5

How can I fix the server crash when specifying an IP in the server.properties file?

NeuroAgent

The main reason a Minecraft Forge server crashes when specifying an IP in the server.properties file is that the server tries to bind to the specified IP address, but this address is unavailable or incorrectly configured. This causes a “Failed to bind to port” error, which leads to the server crashing.

Main causes of crashes
How to fix the problem
Proper server.properties configuration
Additional solutions
Checking connection

Main causes of crashes

The problem occurs for several main reasons:

Incorrect IP address in server.properties
The server tries to bind to an IP address that doesn’t exist on your computer or isn’t available for port binding.
IPv4/IPv6 conflict
This often occurs when specifying an IPv4 address in a system where IPv6 is enabled, or vice versa. The error java.net.UnknownHostException: [IP]:25565: invalid IPv6 address indicates exactly this problem.
Port already in use
Another program or instance of the Minecraft server is already using port 25565 on the specified IP address.
Lack of static IP
If you specify a local IP (for example, 192.168.1.100) but it’s assigned dynamically via DHCP, it may change after a reboot, which will lead to a binding error.

How to fix the problem

The simplest and most effective solution is to leave the IP address field empty in the server.properties file. This will force the server to automatically determine available network interfaces and bind to all available IP addresses.

Fix steps:

Open the server.properties file in a text editor
Find the line server-ip=
Delete the IP address after the equals sign so it looks like this: server-ip=
Save the file
Restart the server

Important: If you want to specify a specific IP address, make sure that:

This IP is actually assigned to your network interface

There are no other services using port 25565 on this IP

You have a static IP address set up

Proper server.properties configuration

Here’s how to properly configure key parameters in the server.properties file for external access:

properties

# Leave empty for automatic IP detection
server-ip=

# Standard Minecraft port
server-port=25565

# For external access, you need to:
# 1. Set up port forwarding on your router
# 2. Open port 25565 in the Windows firewall
# 3. Make sure your ISP isn't blocking the port

If you still want to specify an IP address, use 0.0.0.0 to bind to all interfaces:

properties

server-ip=0.0.0.0
server-port=25565

Additional solutions

If the problem persists after clearing the IP field, try the following methods:

1. Port check

Use the command in Windows command prompt to check who is using port 25565:

cmd

netstat -ano | findstr :25565

If the port is in use, end the process with the corresponding PID or change the port in server.properties.

2. Static IP setup

If you want to use a local IP:

Set a static IP in your network adapter settings
Make sure the IP doesn’t conflict with other devices on the network
Specify this IP in server.properties only after verifying its availability

3. Firewall setup

Open “Windows Defender Firewall”
Advanced settings → Inbound rules
Create a rule for port 25565 (TCP and UDP)
Allow connection for all profiles

Checking connection

After fixing the configuration, check server availability:

Local access: Connect via localhost or 127.0.0.1
Network access: Use your computer’s local IP (for example, 192.168.1.100:25565)
External access: Use your public IP (you can find it at whatismyip.com)

Note: For external access, be sure to set up port forwarding on your router, redirecting port 25565 to your server’s internal IP.

Sources

Conclusion

The main problem with server crashes when specifying an IP is the attempt to bind to an unavailable or incorrectly configured network interface.
The simplest solution is to leave the server-ip= field empty in the configuration file, which will allow the server to automatically determine available interfaces.
For external access, you not only need to properly configure server.properties but also ensure port forwarding on your router and open the port in the firewall.
If you need to specify a specific IP, make sure it’s static, actually exists on your computer, and isn’t being used by other services.
If you encounter problems with port binding, use the command netstat -ano | findstr :25565 to check who is using the port, and if necessary, change the configuration port.

How to check if port 25565 is in use on my Minecraft server?How to set up port forwarding for external access to my Minecraft server through a router?What to do if my Minecraft server won't start after changing the server.properties configuration?How to properly configure a static IP for a Minecraft server in Windows?Which firewalls might block my Minecraft server and how to configure them?How to check if my Minecraft server is accessible from the internet and what to do if it's not?

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