PINGPing the server; returns PONG or echoes the optional message.
| Syntax | PING [message] |
| Group | connection |
| Arity | -1 |
| Since | 1.0.0 |
| Flags | readonly |
| Complexity | O(1) |
| Redis compatibility | differs: kevy has no RESP2 subscriber mode, so PING while subscribed does not switch to the array form and non-pubsub commands stay legal on a subscribed connection |