How to establish communication between multiple robots?

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I am using service-client method here. I have 4 robots running in gazebo simulator. One of them is server while the other three are clients. I need to achieve the following:

1. Client1 will send the data to server.
2. Server will distribute the data equally among client1, client2 and client3.
3. All 3 clients will then operate on the data and send it back to server.
4. Server will organise the received data from all clients and send it back to client1.

How do I go about implementing this situation? I am using Gazebo-2.2.2 in ROS-Indigo.