code: public static synchronized ModbusSlave createTCPSlave(int port, int poolSize, boolean useRtuOverTcp) throws ModbusException {
          return ModbusSlaveFactory.createTCPSlave(null, port, poolSize, useRtuOverTcp);
      }
docs: Creates a TCP modbus slave or returns the one already allocated to this port
  
  @param port          Port to listen on
  @param poolSize      Pool size of listener threads
  @param useRtuOverTcp True if the RTU protocol should be used over TCP
  @return new or existing TCP modbus slave associated with the port
  
  @throws ModbusException If a problem occurs e.g. port already in use