On Technic Launcher, I downloaded both "Forge Slate - 1.12.2" and "empty forge 1.12.2" to use for the client.

I downloaded the mods of WorldEdit for 1.12.2 and Forge Essentials for Forge 1.12.2. I have these on the server too.

To get the server working, I needed Java 8 with the following script:

"E:\Apps\Java\jre1.8.0_351\bin\javaw.exe" -Xmx8192M -Xms8192M -jar server.jar
pause

Now, I cannot get a client to work correctly. I'll explain the problem. I launch the modpack, that works. I go to Multiplayer and see my LocalHost server online. The second I double click to join; it says loading terrain and then the modpack crashes every time. The log in the modpack's directory doesn't make much sense to me.

Please help.

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

-- Head --
Thread: Client thread
Stacktrace:
    at com.forgeessentials.data.v2.DataManager.getInstance(DataManager.java:79)
    at com.forgeessentials.util.PlayerInfo.get(PlayerInfo.java:178)
    at com.forgeessentials.util.PlayerInfo.get(PlayerInfo.java:196)
    at net.minecraft.entity.player.EntityPlayer.redirect$zzd000$onUpdate_NoClip(EntityPlayer.java:2783)
    at net.minecraft.entity.player.EntityPlayer.func_70071_h_(EntityPlayer.java:191)
    at net.minecraft.client.entity.EntityPlayerSP.func_70071_h_(EntityPlayerSP.java:181)
    at net.minecraft.world.World.func_72866_a(World.java:1996)
    at net.minecraft.world.World.func_72870_g(World.java:1958)

-- Entity being ticked --
Details:
    Entity Type: null (net.minecraft.client.entity.EntityPlayerSP)
    Entity ID: 2942
    Entity Name: bradley877
    Entity's Exact location: -15.50, 71.00, 251.50
    Entity's Block location: World: (-16,71,251), Chunk: (at 0,4,11 in -1,15; contains blocks -16,0,240 to -1,255,255), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
    Entity's Momentum: 0.00, 0.00, 0.00
    Entity's Passengers: []
    Entity's Vehicle: ~~ERROR~~ NullPointerException: null
Stacktrace:
    at net.minecraft.world.World.func_72939_s(World.java:1762)

-- Affected level --
Details:
    Level name: MpServer
    All players: 1 total; [EntityPlayerSP['bradley877'/2942, l='MpServer', x=-15.50, y=71.00, z=251.50]]
    Chunk stats: MultiplayerChunkCache: 399, 399
    Level seed: 0
    Level generator: ID 00 - default, ver 1. Features enabled: false
    Level generator options: 
    Level spawn location: World: (-16,64,252), Chunk: (at 0,4,12 in -1,15; contains blocks -16,0,240 to -1,255,255), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
    Level time: 2675 game time, 2675 day time
    Level dimension: 0
    Level storage version: 0x00000 - Unknown?
    Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
    Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
    Forced entities: 71 total; [EntityPlayerSP['bradley877'/2942, l='MpServer', x=-15.50, y=71.00, z=251.50], EntityItem['item.tile.torch'/25, l='MpServer', x=-73.97, y=11.00, z=286.13], EntityPig['Pig'/26, l='MpServer', x=-85.50, y=74.00, z=329.50], EntityPig['Pig'/27, l='MpServer', x=-84.50, y=74.00, z=331.50], EntityPig['Pig'/28, l='MpServer', x=-85.50, y=74.00, z=330.50], EntitySkeleton['Skeleton'/2974, l='MpServer', x=0.50, y=25.00, z=296.50], EntitySquid['Squid'/2978, l='MpServer', x=-54.50, y=61.00, z=203.50], EntitySquid['Squid'/2979, l='MpServer', x=-51.50, y=61.00, z=201.50], EntitySquid['Squid'/2980, l='MpServer', x=-56.50, y=61.00, z=201.50], EntityItem['item.tile.rail'/37, l='MpServer', x=-54.92, y=13.00, z=313.13], EntitySquid['Squid'/2981, l='MpServer', x=-56.50, y=61.00, z=199.50], EntityFallingBlock['Falling Block'/421, l='MpServer', x=-75.50, y=18.30, z=320.50], EntityItem['item.tile.torch'/42, l='MpServer', x=-45.13, y=30.00, z=236.08], EntityPig['Pig'/43, l='MpServer', x=-50.97, y=85.00, z=276.50], EntitySquid['Squid'/2987, l='MpServer', x=-46.50, y=47.00, z=188.50], EntityPig['Pig'/44, l='MpServer', x=-52.48, y=86.00, z=264.73], EntitySquid['Squid'/2988, l='MpServer', x=-45.50, y=47.00, z=188.50], EntityPig['Pig'/45, l='MpServer', x=-28.50, y=66.00, z=316.50], EntitySquid['Squid'/2989, l='MpServer', x=-48.50, y=47.00, z=188.50], EntityPig['Pig'/46, l='MpServer', x=-30.50, y=68.00, z=317.50], EntitySquid['Squid'/2990, l='MpServer', x=-50.50, y=47.00, z=190.50], EntityPig['Pig'/47, l='MpServer', x=-29.50, y=67.00, z=315.50], EntityPig['Pig'/48, l='MpServer', x=-29.49, y=70.00, z=305.69], EntityItem['item.tile.torch'/54, l='MpServer', x=-14.76, y=26.00, z=238.88], EntityItem['item.tile.torch'/55, l='MpServer', x=-13.94, y=26.00, z=239.22], EntityItem['item.item.string'/56, l='MpServer', x=-20.85, y=26.00, z=232.77], EntityItem['item.item.string'/59, l='MpServer', x=-14.13, y=27.00, z=245.32], EntityItem['item.tile.torch'/700, l='MpServer', x=-17.87, y=28.00, z=265.88], EntityItem['item.item.string'/62, l='MpServer', x=-16.76, y=27.00, z=244.13], EntityItem['item.item.string'/64, l='MpServer', x=-19.13, y=27.00, z=248.25], EntityItem['item.tile.rail'/66, l='MpServer', x=-14.13, y=27.00, z=245.29], EntityItem['item.tile.torch'/67, l='MpServer', x=-20.16, y=28.00, z=255.32], EntityMinecartChest['Minecart with Chest'/68, l='MpServer', x=-9.50, y=26.06, z=253.50], EntityItem['item.tile.torch'/69, l='MpServer', x=-13.05, y=26.00, z=300.13], EntityMinecartChest['Minecart with Chest'/70, l='MpServer', x=-15.50, y=29.06, z=330.50], EntityItem['item.tile.torch'/79, l='MpServer', x=-0.07, y=25.00, z=310.67], EntityItem['item.tile.torch'/89, l='MpServer', x=19.41, y=26.00, z=227.23], EntityItem['item.tile.rail'/90, l='MpServer', x=20.88, y=26.00, z=224.23], EntityItem['item.tile.rail'/91, l='MpServer', x=18.13, y=26.00, z=217.13], EntityItem['item.tile.gravel'/2907, l='MpServer', x=-59.58, y=16.00, z=288.77], EntityItem['item.tile.rail'/92, l='MpServer', x=20.88, y=26.00, z=217.13], EntityItem['item.tile.rail'/93, l='MpServer', x=19.45, y=26.00, z=227.54], EntityItem['item.tile.gravel'/2911, l='MpServer', x=-53.59, y=16.00, z=299.26], EntityFallingBlock['Falling Block'/1503, l='MpServer', x=-75.50, y=18.31, z=320.50], EntityItem['item.tile.gravel'/2913, l='MpServer', x=-54.31, y=15.00, z=303.31], EntityPig['Pig'/97, l='MpServer', x=38.50, y=66.00, z=192.50], EntityPig['Pig'/98, l='MpServer', x=42.49, y=66.00, z=191.78], EntityItem['item.tile.gravel'/2915, l='MpServer', x=-38.16, y=30.00, z=238.88], EntityPig['Pig'/99, l='MpServer', x=39.45, y=64.00, z=194.50], EntityPig['Pig'/100, l='MpServer', x=39.50, y=64.00, z=195.50], EntityPig['Pig'/101, l='MpServer', x=38.50, y=67.00, z=209.50], EntityPig['Pig'/102, l='MpServer', x=38.50, y=67.00, z=210.50], EntityPig['Pig'/103, l='MpServer', x=38.50, y=67.00, z=209.50], EntityPig['Pig'/104, l='MpServer', x=18.26, y=87.00, z=307.83], EntityItem['item.tile.gravel'/2921, l='MpServer', x=-60.13, y=15.00, z=286.88], EntityPig['Pig'/105, l='MpServer', x=19.73, y=97.00, z=311.51], EntityItem['item.tile.gravel'/2922, l='MpServer', x=-52.43, y=16.00, z=299.73], EntityPig['Pig'/106, l='MpServer', x=22.55, y=92.00, z=307.55], EntityPig['Pig'/107, l='MpServer', x=19.18, y=89.00, z=307.33], EntityFallingBlock['Falling Block'/491, l='MpServer', x=-52.50, y=17.31, z=304.50], EntityItem['item.tile.gravel'/2924, l='MpServer', x=-51.51, y=16.00, z=299.13], EntityItem['item.tile.gravel'/2926, l='MpServer', x=-39.36, y=30.00, z=238.36], EntityItem['item.tile.gravel'/2928, l='MpServer', x=-58.13, y=16.00, z=288.13], EntityItem['item.tile.gravel'/2929, l='MpServer', x=-60.77, y=16.00, z=288.96], EntityItem['item.tile.gravel'/2931, l='MpServer', x=-62.16, y=16.00, z=289.16], EntityPig['Pig'/118, l='MpServer', x=48.45, y=72.00, z=215.45], EntityPig['Pig'/119, l='MpServer', x=51.50, y=72.00, z=218.50], EntityPig['Pig'/120, l='MpServer', x=52.50, y=72.00, z=219.50], EntityItem['item.tile.gravel'/2937, l='MpServer', x=-58.13, y=16.00, z=289.42], EntityPig['Pig'/121, l='MpServer', x=55.50, y=72.00, z=219.50], EntityItem['item.tile.gravel'/2938, l='MpServer', x=-60.88, y=15.00, z=286.25]]
    Retry entities: 0 total; []
    Server brand: fml,forge
    Server type: Non-integrated multiplayer server
Stacktrace:
    at net.minecraft.client.multiplayer.WorldClient.func_72914_a(WorldClient.java:420)
    at net.minecraft.client.Minecraft.func_71396_d(Minecraft.java:2741)
    at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:419)
    at net.minecraft.client.main.Main.main(SourceFile:123)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

The version you are using is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.

Currently supported versions are 1.19.2 (Latest) and 1.18.2 (LTS).