Moxa Technologies DE-304 Installation Guide download pdf (Page 23)

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.

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Moxa Technologies DE-304 Installation Guide Page 23