Engine.IO Server Library for Java
LaunchDarkly Server-Side SDK for Java
Blynk is an Internet of Things Platform aimed to simplify building mobile and web applications for the Internet of Things. Easily connect 400+ hardware models like Arduino, ESP8266, ESP32, Raspberry Pi and similar MCUs and drag-n-drop IOT mobile apps for iOS and Android in 5 minutes
Fake implementation of MongoDB in Java that speaks the wire protocol.
Free and open source log management
Java language server
Breeze support for java servers