1. Do not frequent opening and closing the serial port, this is a time-consuming process, if multiple stations are competing for serial resources, Caton occurs, the deadlock.
2. PLC to read and write estimated 100 milliseconds, if concurrent write, write and some will fail, you need to Delay or try again.
3. Typically a station of an operation (start / stop / pause / state /) will use one bit to identify a byte, byte you can use batch write / read (multiple of 8), so much faster.
4. Laptop no COM port, COM can buy CABLE USB female port.
5. Multi-threaded how to allocate (according to the com port, PLC read a write a, UI a)? ? ?
6. PLC, with a small touch screen, you can direct the secondary development (only for small amounts of data, hard to deal with large volumes of data. Multiport Serial not a good deal)