[ansible] How to copy files between two nodes using ansible

To copy remote-to-remote files you can use the synchronize module with 'delegate_to: source-server' keyword:

- hosts: serverB
  tasks:    
   - name: Copy Remote-To-Remote (from serverA to serverB)
     synchronize: src=/copy/from_serverA dest=/copy/to_serverB
     delegate_to: serverA

This playbook can run from your machineC.