public boolean isPingMessage(byte[] buffer) {
    return buffer.length == 4
        && (buffer[0] == 'p' && buffer[1] == 'i' && buffer[2] == 'n' && buffer[3] == 'g');
  }
GMSPingPonger is used to detect whether a member exists by sending UDP Ping and Pong
messages. A member can send a Ping message to another member and receive a Pong message
in response. GMSPingPonger is largely used to detect whether a quorum of the cluster
is reachable.
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/messenger/GMSPingPonger.java