Official Mojang links often auto-update to the latest version. To get the specific 1.8.1 version:
Open your Minecraft Launcher, go to "Installations," create a new 1.8.1 profile, and look for the "Server" download link next to the version selection.
Move the downloaded .jar or .exe file into your dedicated folder.
For version 1.8.1, Java 8 is recommended for maximum compatibility.
Installing a Minecraft Server: Ultimate Guide Tips and Tricks
If you want plugins, you might consider Bukkit or Spigot 1.8.1. 3. Initial Setup & EULA
You are looking for a file named minecraft_server.1.8.1.jar or minecraft_server.1.8.1.exe .
Set to false if you want to allow players with non-premium accounts to join. difficulty: Change from 1 (Easy) to 2 (Normal) or 3 (Hard). motd: This is the message players see in their server list. 5. Joining the Server