A library for implementing your own protocol (RPC API) in Java?

Question

Java

A Windows computer communicates with a device connected via a COM port.
A lot of different teams are planned. And the formats of "communication" are also different: somewhere it is a "question-answer" from the computer, somewhere from the device, somewhere from the heartbeat from the computer, somewhere from the device.
It would not be desirable to fence all this protocol with a bicycle based on bare COM. After all, some languages ​​have ready-made libraries for building an RPC API based on building a transport.
The "packages" format can be JSON, but is not required. The quality of the library is more important.
And it doesn’t have to be for COM ports at all. Even if it does not support such transport at all, but the library is good and the source code is there, then why not file it under it? Better than making a bike.
Don't worry about the device. This library will be ported under it.