Communication with java server

Hello guys, I'm doing a videogame project for my university. They already have some games made with libgdx in java and I'm the first one who did it in Unity.

The main problem is that the API for the communication between client and server (it uses JSON) is written in java.

Is there any way to run java code from c# script and to directly use their API?

Should I maybe rewrite the client API in c# (as it's very similar to java and it shouldn't take that much) and communicate with the java server? Is this possible? If yes, is this possible directly with Unity or should I use NET sockets?

Or is there anything else that you suggest me to do?

Thanks a lot for you help :)