Question: SMP Issue?

I run a server on my laptop for a friend and I to play Minecraft together.

I have installed the IC2 mod into the minecraft_server.jar file as per the instructions, however I get an error when I try and log into the server: java.io.IOException: Bad packet id 230

My question is this: What have I done wrong? Do I have to install all the client side thing for the server side to properly work or did I miss something blatantly obvious?

It's a hamachi server I run on my laptop, and I play minecraft while running the server at the same time, no issues before trying to install the mod.

Any and all help will be appreciated. Thank you.

I have. The server is running fine, it seems. I just cannot connect to it from my minecraft client. Does this mean that I have to install all the client side things so that it will work on the server? If so, do I have to have my friend install all the client side things as well?

The steps I took to do it all are as follows:
downloaded a new and fresh minecraft_server.jar
downloaded ModloaderMP 1.8.1 Server.zip.
---used 7zip to open archive of minecraft_server.jar and ModloaderMP 1.8.1 Server.zip and copied MLMP into the server.jar
downloaded modloadermpserver-fix.7z
---used 7zip to open archive of server.jar and MLMPfix and copied MLMPfix into server.jar
downloaded minecraftforge-server-1.1.1.zip
---used 7zip to open archive of server.jar and Forge and copied Forge into server.jar
downloaded Industrialcraft-2-server_1.15.jar
--- put IC2 server.jar into 'mods' folder in my minecraft server folder after running the server once to create said 'mod' folder.

Did I miss something? I've added no content to my client side minecraft.jar folder, it is vanilla. I'm hoping there is something simple that can be done to fix this and I'm hoping it's my own stupidity that is causing this. Wouldn't be the first time my dumbass didn't figure something simple out

Yup, that did it... I really am a dumbass. And one good dumbass question deserves another!

Do I have to get my friend to install this mod on her end or will it simple being on the server and my client be good enough?

Thanks bunches guys.