Moxa Technologies NPort Server Lite DE-302, Hardware Installation Manual

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4-5
Programming Problems
Why do the Win32 COMM API functions return fail, or the PComm Pro
library functions return the fail code “SIO_WIN32 FAIL”?
The fail code for the COMM API functions implies something different than
the fail code received from the standard COM driver. For example, you get
the fail code when the network connected to the device server is unreachable,
or the device server is offline. If the network connection is through the
Internet, the network could be unreachable if Internet traffic is jammed. This
does not mean you have a defective device server. To recover from this type
of error, you can modify your program so that the port is automatically
closed and then re-opened.
You should also check the following to make sure that the problem is only
with the TCP/IP network:
1. If the device server is off-line, turn it on and plug it into the network.
You may test if the route to NPort Server Lite is reachable by typing
Ping [NPort-Server-Lite-IP-address]
If a route to the device server cannot be established, check your host’s
routing table and the device server's routing table.
To solve this problem, programs should:
1. Try to re-open the port if the fail code is returned during the open (i.e.,
sio_open) session.
2. If the fail code returns while writing data, reading data, changing settings,
etc., you should close the file handler, and then try to reopen the port.