I'd like to know what should i do to send and receive data from a PLC through the comm port.
I already have the ASCII characters i want to send, yet i dunno how.

 

Do you think that every brand and model of PLC handles serial communications the same way? Some models don't even allow serial port access through their programs.

In order to get a good answer you need to ask a good question. In this case, a good question will include details about the brand and model of PLC you're using and whether the serial port is on the CPU or on a module.

Once you've defined that, somebody with experience on that specific PLC may be able to offer you some tips to get started.

 

The PLC manufacturer may have software that lets you send data to thier plc through com port. OPC servers are commonly used, or they will have a manual describing a communication protocal and you can just use Microsofts Read/Write functions to send/receive data on the com port.

 

Look at Matrikon OPC Genie - this is a configurable OPC server that allows you to read/write data over either a serial port or a TCP port.

You can implement a protocol in a very short amount of time Without having to write code.

William F. Hullsiek