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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
It's not written in Java, but if you want to look at some source code and/or protocols to see how it's already been done, look at mpd (https://www.musicpd.org/). IIRC, it actually uses TCP.
NOTE:
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