Define the Settings for COM Ports and TCP/IP Connections

The COM port and TCP/IP connection settings define how ClearSCADA reacts to a driver being unable to assign to a COM port or TCP/IP socket. They also define the number of conditions that can cause a channel (that is associated with a port/socket) to be deemed as failed.

When ClearSCADA detects that a channel has failed, it raises an alarm (if configured to do so) and the channel de-assigns from the port or socket. After the specified time period, the driver attempts to re-assign the port or socket.

The default COM ports and TCP/IP Connections settings are usually appropriate, but you may need to change the settings if:

• ClearSCADA is taking too long to re-assign to a COM port or TCP/IP socket that failed on the previous attempt
• ClearSCADA is re-assigning the COM port or TCP/IP socket too quickly.
• You only want a COM port to be deemed as failed when a specific number of consecutive read or write attempts have failed. This allows ClearSCADA to continue using a COM port when there are intermittent failures.
• You only want a COM port or TCP/IP connection to be deemed as failed when a specific number of consecutive read or write timeouts have failed. This allows ClearSCADA to continue using a COM port or TCPIP connection when there are intermittent failures.
• You only want to allow a COM port or TCP/IP connection a greater time interval to perform a graceful socket shutdown.

To change the COM port and TCP/IP settings, see the following sections:

• Define the Period Between Retries to Assign to a Port/Socket
• Define the Delay After Calling Comtrol’s Freeport Routine
• Define the Maximum Number of Consecutive Failed Reads and Writes
• Define the Maximum Number of Consecutive Read and Write Timeouts
• Graceful Network Socket Shutdown Timeout