RModbus - RTU Timeout won't reset after the first time out happened

Question

I have two RS485 Modbus RTU Servers. Reading works fine but when I disconnect the second server, RModbus also shows timeout messages for the first server after a second read attempt. After the first timeout, RModbus stops working.

What is wrong?

port = "COM6"
baud = 19200
uid = 1
options = {data_bits: 8, stop_bits: 1, parity: SerialPort::EVEN} 

cl = ModBus::RTUClient.new(port, baud, options)
cl.read_retries = 2
cl.debug = true

# Works fine
begin
    puts cl.with_slave(1).read_holding_registers(512, 1)
rescue => error
    puts error.message
end

# Intended Timeout
begin
    puts cl.with_slave(2).read_holding_registers(512, 1)
rescue => error
    puts error.message
end

# Should work, however, issues a timeout.
begin
    puts cl.with_slave(1).read_holding_registers(512, 1)
rescue => error
    puts error.message
end

Answer 1

In a Modbus RTU network can only exist one master.

Serial communication has no means for avoiding collisions.

It is the single master that must manage the communications following a strict order: request >> wait for a response >> request >> wait for a response...