: The official Mojang server software. You can find legacy files on archival sites like MCVersions.net .
To run a server for version 1.3.1, you should use the software available at that time: server mainkraft 1 3 1 skachat
: While Spigot is the basis for Paper, its 1.3.1 support is limited as it gained significant traction later in 2012. How to Set Up a 1.3.1 Server : The official Mojang server software
If you are looking for modern performance and features, you will need to update your client to at least version 1.8.8 to use PaperMC . How to Set Up a 1
: The eula.txt requirement was added in later versions (1.7.10+). For 1.3.1, the server should generate its files and start immediately without this step.
: Legacy Minecraft versions like 1.3.1 are designed for older Java environments (specifically Java 7). Modern Java versions may cause crashes.