Universal Peace and Hello was a standard message sent by Starfleet starships to approaching unidentified starships and probes. The message would be sent in all known languages and on all known frequencies to the other ship. This message would inform the receiver that the sender was a friendly ship.
In 2286, the USS Saratoga sent this message to the Whale Probe. After negative feedback from the probe, the ship's captain sent a message to Starfleet Command informing them of their status. (Star Trek IV: The Voyage Home)