Hello! I am still very new to creating servers but today I was trying to make one so that me and my brother could play with mods.
I created a forge server and allowed it to install, I also made a run.bat file though had to delete it afterwards as it stopped working, not sure why. Now the server itself does work, but whenever I try to place a modded block it just seems to vanish
here are my latest logs: 
[19:21:45] [Server thread/INFO]: Starting minecraft server version 1.12.2
[19:21:45] [Server thread/INFO]: Loading properties
[19:21:45] [Server console handler/ERROR]: Exception handling console input
java.io.IOException: The handle is invalid
    at java.io.FileInputStream.readBytes(Native Method) ~[?:?]
    at java.io.FileInputStream.read(Unknown Source) ~[?:?]
    at java.io.BufferedInputStream.read1(Unknown Source) ~[?:?]
    at java.io.BufferedInputStream.read(Unknown Source) ~[?:?]
    at sun.nio.cs.StreamDecoder.readBytes(Unknown Source) ~[?:?]
    at sun.nio.cs.StreamDecoder.implRead(Unknown Source) ~[?:?]
    at sun.nio.cs.StreamDecoder.read(Unknown Source) ~[?:?]
    at java.io.InputStreamReader.read(Unknown Source) ~[?:?]
    at java.io.BufferedReader.fill(Unknown Source) ~[?:?]
    at java.io.BufferedReader.readLine(Unknown Source) ~[?:?]
    at java.io.BufferedReader.readLine(Unknown Source) ~[?:?]
    at nz$2.run(SourceFile:100) [minecraft_server.1.12.2.jar:?]
[19:21:45] [Server thread/INFO]: Default game type: SURVIVAL
[19:21:45] [Server thread/INFO]: Generating keypair
[19:21:45] [Server thread/INFO]: Starting Minecraft server on 192.168.0.150:25565
[19:21:45] [Server thread/INFO]: Using default channel type
[19:21:46] [Server thread/INFO]: Preparing level "world"
[19:21:46] [Server thread/INFO]: Loaded 488 advancements
[19:21:46] [Server thread/INFO]: Preparing start region for level 0
[19:21:47] [Server thread/INFO]: Preparing spawn area: 48%
[19:21:48] [Server thread/INFO]: Done (1.771s)! For help, type "help" or "?"
[19:22:01] [User Authenticator #1/INFO]: UUID of player Nyxistaken is 0609cbac-80f9-45a0-8fe0-0c261d3ef31b
[19:22:01] [Server thread/INFO]: Nyxistaken[/192.168.0.150:55368] logged in with entity id 190 at (37.5, 63.0, 252.5)
[19:22:01] [Server thread/INFO]: Nyxistaken joined the game
[19:22:33] [Server thread/INFO]: Set Nyxistaken's game mode to Survival Mode
[19:22:47] [Server thread/INFO]: Set Nyxistaken's game mode to Creative Mode

I have about 13 mods that I am using including an NPC mod and the Aether mod. My brother has these installed as well, I have them installed on my main game and in the server folder so I'm not sure why it isn't working

You won't get any support since 1.12.x is not supported any more on this forum you need to use a higher version of minecraft 1.14.x - 1.16.1
Note: If anyone would help you they would need your debug.log log and not this one

Alright, but I don't think any of the server stuff changes too much with the version, I just need a hand

I don't know if anything change or not most likely it changes but you still won't get any help and the topic will be closed

Are your mod(s) installed both on the client and server side?

 

Nevermind, just found my answer

Edited August 15, 20205 yr by Huskabyte
Realized the answer was in your original post.

Ah! Wait! Are you running the wrong server jar? You need to run the forge jar file using a command prompt or terminal of sorts, not the minecraft server jar file.

1 hour ago, Nyxistaken said:

[19:21:45] [Server thread/INFO]: Starting minecraft server version 1.12.2
[19:21:45] [Server thread/INFO]: Loading properties
[19:21:45] [Server console handler/ERROR]: Exception handling console input
java.io.IOException: The handle is invalid
    at java.io.FileInputStream.readBytes(Native Method) ~[?:?]
    at java.io.FileInputStream.read(Unknown Source) ~[?:?]
    at java.io.BufferedInputStream.read1(Unknown Source) ~[?:?]
    at java.io.BufferedInputStream.read(Unknown Source) ~[?:?]
    at sun.nio.cs.StreamDecoder.readBytes(Unknown Source) ~[?:?]
    at sun.nio.cs.StreamDecoder.implRead(Unknown Source) ~[?:?]
    at sun.nio.cs.StreamDecoder.read(Unknown Source) ~[?:?]
    at java.io.InputStreamReader.read(Unknown Source) ~[?:?]
    at java.io.BufferedReader.fill(Unknown Source) ~[?:?]
    at java.io.BufferedReader.readLine(Unknown Source) ~[?:?]
    at java.io.BufferedReader.readLine(Unknown Source) ~[?:?]
    at nz$2.run(SourceFile:100) [minecraft_server.1.12.2.jar:?]
[19:21:45] [Server thread/INFO]: Default game type: SURVIVAL
[19:21:45] [Server thread/INFO]: Generating keypair
[19:21:45] [Server thread/INFO]: Starting Minecraft server on 192.168.0.150:25565
[19:21:45] [Server thread/INFO]: Using default channel type
[19:21:46] [Server thread/INFO]: Preparing level "world"
[19:21:46] [Server thread/INFO]: Loaded 488 advancements
[19:21:46] [Server thread/INFO]: Preparing start region for level 0
[19:21:47] [Server thread/INFO]: Preparing spawn area: 48%
[19:21:48] [Server thread/INFO]: Done (1.771s)! For help, type "help" or "?"
[19:22:01] [User Authenticator #1/INFO]: UUID of player Nyxistaken is 0609cbac-80f9-45a0-8fe0-0c261d3ef31b
[19:22:01] [Server thread/INFO]: Nyxistaken[/192.168.0.150:55368] logged in with entity id 190 at (37.5, 63.0, 252.5)
[19:22:01] [Server thread/INFO]: Nyxistaken joined the game
[19:22:33] [Server thread/INFO]: Set Nyxistaken's game mode to Survival Mode
[19:22:47] [Server thread/INFO]: Set Nyxistaken's game mode to Creative Mode

This is a vanilla server. To start a modded server you have to start the forge jar.

59 minutes ago, Danebi said:

This is a vanilla server. To start a modded server you have to start the forge jar.

I just figured that out with a video, but when I try to launch the forge jar this is what I get
 

C:\Users\Filip\Desktop\Minecraft Server>java -Xmx4096M -Xms4096M -jar forgeserver.jar nogui
A problem occurred running the Server launcher.java.lang.reflect.InvocationTargetException
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.base/java.lang.reflect.Method.invoke(Unknown Source)
        at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.run(ServerLaunchWrapper.java:70)
        at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.main(ServerLaunchWrapper.java:34)
Caused by: java.lang.ClassCastException: java.base/jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to java.base/java.net.URLClassLoader
        at net.minecraft.launchwrapper.Launch.<init>(Launch.java:34)
        at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
        ... 6 more

C:\Users\Filip\Desktop\Minecraft Server>PAUSE
Press any key to continue . . .

and that's after having changed the file name to forgeserver and the run task to forgeserver.jar 
If I keep the same names as default on run.bat I end up with a "click a key to continue" without any other info
the thing just doesn't launch

What version of java do you have?

35 minutes ago, Danebi said:

What version of java do you have?

I'm not sure, I installed it quite a wee while ago. Tbh I haven't touched MC until a few weeks ago when my brother bought it, hence why I wanted to make a server with mods (LAN connection kept timing out or having weird errors)

Downloaded the latest version and now I am getting this:
 

C:\Users\Filip\Desktop\Minecraft Server>java -Xmx4096M -Xms4096M -jar forgeserver.jar nogui
Invalid maximum heap size: -Xmx4096M
The specified size exceeds the maximum representable size.
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

C:\Users\Filip\Desktop\Minecraft Server>PAUSE
Press any key to continue . . .

Have you installed java 32 bit or 64 bit?

Edited August 15, 20205 yr by Danebi

I also believe Minecraft is best on Java 8.

I’m not sure. I think 64? Also I was able to manually open the forge server file this time, though after a few minutes the client crashes without showing any error messages 

I'm pretty sure you have java 32 bit. You can check using java -version

And if your game crashed post debug.log.

Edited August 15, 20205 yr by Danebi