title: Pymodbus (Serial) over a tcp serial connection
body: <p>I will be creating a connection between my Linux server and a cellular modem where the modem will act as a server for serial over TCP.</p>
  
  <p>The modem itself is connected to a modbus device (industrial protocol) via an RS232 connection.</p>
  
  <p>I would like to use pymodbus to facilitate talking to the end modbus device. However, I cannot use the TCP modbus option in PyModbus as the end device speaks serial modbus (Modbus RTU). And I cannot use the serial modbus option in Pymodbus as it expects to open an actual local serial port (tty device) on the linux server.</p>
  
  <p>How can I bridge the serial connection such that the pymodbus library will see the connection as a local serial device?</p>