from nx_tcp.h:319
VOID _nx_tcp_packet_send_control(NX_TCP_SOCKET *socket_ptr,
ULONG control_bits,
ULONG tx_sequence,
ULONG ack_number,
ULONG option_word_1,
ULONG option_word_2,
UCHAR *data);
Implemented in nx_tcp_packet_send_control.c:90