We are ready to buy Open Source code. We want to implemented secure communication between two hazelcast or across all hazelcast which are on same network.
Please let's know how it possible,
I think your question was already answered in github (https://github.com/hazelcast/hazelcast/issues/8370). Hazelcast Opensource does not have transport layer security builtin. This is an enterprise feature but it certainly is possible to build it yourself (keyword NodeExtension).
For more details, see the linked github issue.