jServer3 library is the previous version of jServer library. It is the library that was included with B4J up until B4J v9.80.
Starting from B4J v9.80, the included jServer library is jServer 4: https://www.b4x.com/android/forum/threads/jserver-v4-0-based-on-jetty-11.140437/#content.
Main difference is that jServer 4 depends on Java 11+.
Download link: https://www.b4x.com/b4j/files/jServer3.zip
Starting from B4J v9.80, the included jServer library is jServer 4: https://www.b4x.com/android/forum/threads/jserver-v4-0-based-on-jetty-11.140437/#content.
Main difference is that jServer 4 depends on Java 11+.
Download link: https://www.b4x.com/b4j/files/jServer3.zip