Comport can be either a physical device, like the serial port (COM1, COM2, etc), IO card, a virtual path to a device (like a TCP/IP connection over as network) or an application interface like OPC or DDE.
Application Programming Interface. This is a "virtual" port. This is a proprietary software package commonly used to communicate with proprietary IO cards. Examples include Siemens S7 protocol. Does not correspond to specific IO card or comport number.
For a description of the data entry fields for an API see, section 3.3.5 API Comport Properties
SNMP, DDE, OMRON and Siemens S7 interfaces use the API ComPort type.
OLE for Process Control. This is an Industry Standard Communications Standard. This is a "virtual" port. OPC is commonly used to communicate with proprietary IO cards and third party software packages. Does not correspond to specific IO card or comport number.
For a description of the data entry fields for an OPC interface, see section 3.3.6 OPC Comport Properties
Allen-Bradley RSLINX. This a "virtual" port used to communicate with proprietary IO cards and proprietary networks supplied by Allen-Bradley (DataHighway, DataHighway Plus, ControlNet, etc.) and PLC 5 and SLC 500 series controllers. Does not correspond to specific IO card or comport number. RSLINX software must be installed on the SCADA node to use the RSLINX ComPort Type.
Note that WebAccess supplies a "native" driver that communicates using DF1 protocol over a Serial Port. This Serial Driver to PLC5 and SLC500 is at no cost and is supplied with WebAccess. It is reputedly faster than the RSLINX driver.
Standard Serial Communications Port using the IBM standard for Personal Computers (RS232-C, RS-422 or RS4-85). Selecting Serial means to access the serial Comport with this number. For example, to use COM2 on the SCADA node, Port2 in the WebAccess Project must be configured as Serial.
For a description of the data entry fields for a Serial Interface, see Serial Interface and section 3.3.3 Serial ComPort Properties.
TCP/IP (transmission Control Protocol / Internet Protocol). Specifies a "Virtual Port" that uses the TCP/IP service installed. Does not correspond to specific IO card or comport number. Will access any IO card that uses the TCP/IP service installed on your PC.
For a description of the data entry fields for a TCP/IP Network Interface see, section 3.3.4 TCP/IP Com Port Properties.