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Transmission parameters can be set for four modes, as when setting the "Serial" and "Serial Line Redundant" lines.
Parameter "ConstOpen"
The meaning of the "ConstOpen" parameter is different from the serial line. The is ignored - TCP connection is established when the first time it is used.line is used for the first time and remains established (except for behavior in redundancy - see Operation of the line in redundancy).
If "ConstOpen" is checked for Line mode 1, when establishing a connection the KOM process waits for responses to all RFC2217 queries. If all responses are not received, the connection is closed.
If "ConstOpen is unchecked for Line mode 1, when establishing a connection the KOM process does not wait for responses (except for the response to the initial WILL CPO, which detects RFC2217 support), so the connection will also work against servers that ignore some of the queries.
The following RFC2217 parameters are queried when establishing a connection:
- SIGNATURE (device identification, eg "MOXA").
- BAUDRATE (speed, eg 9600 baud)
- DATASIZE (number of bits, eg 8)
- PARITY (parity, e.g. even/odd)
- STOPSIZE (number of stop bits)
- signal states - BREAK, DTR, RTS, flow control (XON / XOFF, hardware, DCD, DTR, DSR)
and the following RFC2217 parameter are set:
- LINESTATE (setting of line status reporting - e.g. timeout error, framing error, parity error, overrun error, break-detect error)
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In redundant systems (redundant D2000 servers and/or multiple instances of KOM processes), only the active KOM process connected to the D2000 Server in the HOT state opens a TCP connection. Once it becomes passive, the connection to the device is closed.
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