void sendRequest(final @NotNull DataOutputStream out, final short ordinalVersion,
      final @NotNull Object request) throws IOException {
    out.writeInt(TcpServer.GOSSIPVERSION);
    out.writeShort(ordinalVersion);
    objectSerializer.writeObject(request, out);
    out.flush();
  }
Writes and flushes the header and request object to the server.
geode-tcp-server/src/main/java/org/apache/geode/distributed/internal/tcpserver/TcpClient.java