The P2P protocol in the Hyperledger Fabric is built using google RPC (gRPC). It uses protocol buffers to define the structure of the messages.

Messages are passed between nodes in order to perform various functions. There are four main types of messages in Hyperledger Fabric: discovery, transaction, synchronization, and consensus. Discovery messages are exchanged between nodes when starting up in order to discover other peers on the network. Transaction messages are used to deploy, invoke, and query transactions, and consensus messages are exchanged during consensus. Synchronization messages are passed between nodes to synchronize and keep the blockchain updated on all nodes.