private void rejectUnknownProtocolConnection(Socket socket, int gossipVersion) {
    try {
      socket.getOutputStream().write("unknown protocol version".getBytes());
      socket.getOutputStream().flush();
      socket.close();
    } catch (IOException e) {
      logger
          .debug("exception in sending reply to process using unknown protocol " + gossipVersion,
              e);
    }
  }
Reads the next 3 bytes of the gossip version where first byte was 0.
geode-tcp-server/src/main/java/org/apache/geode/distributed/internal/tcpserver/TcpServer.java