In IRC connections the Server sends a PING command to the client and if everything is right the client should send a PONG command to the server. This is how IRC determines if a client is still connected to the server.
From RFC 2812
The PING command is used to test the presence of an active client or
server at the other end of the connection. Servers send a PING
message at regular intervals if no other activity detected coming
from a connection. If a connection fails to respond to a PING
message within a set amount of time, that connection is closed. A
PING message MAY be sent even if the connection is active.
What I think @BarryCarlyon is trying to say is that you can send a PING [edited] without previously receiving a PING from the server. The PING would still reach the server, the server would respond with a PONG and “refresh” your connection time.