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Permissioning and peers

Use permissioning and peer services to influence network access or interact with peer connections.

Permissioning​

PermissioningService lets plugins register providers for:

  • Node connection permissioning - Restrict node access to known participants only.
  • Transaction permissioning - Restrict transaction processing based on transaction properties.
  • Node message permissioning - Propagate different types of devP2P messages to particular nodes. For example, this can be used to prevent pending transactions from being forwarded to other nodes.

For example, register a node connection permissioning provider:

@Override
public void register(final ServiceManager context) {
  this.serviceManager = context;
  serviceManager
      .getService(PermissioningService.class)
      .ifPresent(
          permissioning ->
              permissioning.registerNodePermissioningProvider(nodeConnectionProvider));
}

The plugin supplies the provider implementation.

Peers​

P2PService exposes methods to:

  • Enable or disable discovery.
  • Get peer counts and peer connections.
  • Subscribe to peer connect and disconnect events.
  • Subscribe to messages for a capability.
  • Send messages to peers.
  • Disconnect peers.

Use P2PService for plugins that need peer visibility or direct peer interactions.

For example, read the current peer count and subscribe to connection events:

@Override
public void start() {
  serviceManager
      .getService(P2PService.class)
      .ifPresent(
          p2p -> {
            int peerCount = p2p.getPeerCount();
            p2p.subscribeConnect(connection -> {});
            p2p.subscribeDisconnect((connection, reason, initiatedByPeer) -> {});
          });
}