How to work in Lua with bytes in port?

Question

UART

There are two certain controllers. These controllers have ports (RS485, but not the essence) that are interconnected. Several simple devices on the MK are also connected there. One controller can throw bytes, the second controller can receive them. On Linux controllers (closed a little more than completely) and LUA. There is nothing more.
Attention, the question is: How can I send and receive in Lua not a character, not a string, but just a byte or several bytes in hexadecimal representation? Those. I send 0x15, and on the other controller I also receive 0x15.
So far, I've been tormented for an hour, and I get anything but 0x15. I did not understand whether he converts it into something when sending it, or when receiving it.
Shipping:

require('serial')
port = serial.open('/dev/RS485-2', {
  baudrate = 115200,
  databits = 8,
  stopbits = 1,
  parity = 'none',
  duplex = 'half'
})
port:write(0x15)
port:close()

Reception:

require('serial')
port2 = serial.open('/dev/RS485-3', {
  baudrate = 115200,
  databits = 8,
  stopbits = 1,
  parity = 'none',
  duplex = 'half'
})
data = port2:read(1)
byte=string.byte(data)

log(string.format("%o, %x, %d", byte,byte,byte))
port2:close()

Answer 1

Dealt with the same problem.
data = port2:read(1) should be like this data = port2:read(1, 1) the second unit is the time to wait for data. and be sure to reset the port after or before the port:flush() session