title: Can't connect to modbus RTU over TCP. What is wrong?
body: <p>Prove that device is working: <code>./modpoll -m enc -p4660 -t4:float -r60 -a3 192.168.1.1</code>:</p>
  
  <pre><code>Protocol configuration: Encapsulated RTU over TCP
  Slave configuration...: address = 3, start reference = 60, count = 1
  Communication.........: 192.168.1.1, port 4660, t/o 1.00 s, poll rate 1000 ms
  Data type.............: 32-bit float, output (holding) register table
  
  TRACELOG: Set poll delay 0
  TRACELOG: Set port 4660
  TRACELOG: Open connection to 192.168.1.1
  TRACELOG: Configuration: 1000, 1000, 0
  -- Polling slave... (Ctrl-C to stop)
  TRACELOG: Read multiple floats 3 60
  TRACELOG: Send(6): 03 03 00 3B 00 02 
  TRACELOG: Recv(9): 03 03 04 6E 08 42 F7 35 FF 
  [60]: 123.714905
  </code></pre>
  
  <p>And how I try to get the connection with <code>pymodbus</code> library:</p>
  
  <pre><code>from pymodbus.client.sync import ModbusTcpClient
  from pymodbus.transaction import ModbusRtuFramer
  
  ModbusTcpClient(host='192.168.1.1', port=4660, framer=ModbusRtuFramer, timeout=5)
  client.connect() # returns True
  client.read_holding_registers(60, count=3, unit=0x03)
  </code></pre>
  
  <p>And get this result:</p>
  
  <pre><code>pymodbus.exceptions.ConnectionException: Modbus Error: [Connection] 192.168.1.1:4660
  Modbus Error: [Connection] 192.168.1.1:4660
  </code></pre>
  
  <p>What I'm doing wrong?</p>