Are CTS and RTS necessary on UART port?
You may be able to just ignore these signals. CTS (Clear To Send) and RT (Request To Send) provide a handshaking mechanism so that each device can tell the other when it's ready to receive data.

However, many Uarts don't implement this and either assume the other end can take data at any time or use another method such as XON/XOFF

Hardware handshaking with RTS/CTS is not used very often on modern equipment but you will need to check the manual, a few devices still require it.