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Error 500 is a general device specific error, the cause of the error is unknown and it just means that the messages could not be sent. This error has nothing to do with the problems in your first post. The Huawei E173 works fine but for some reason it just can't send the message.

Since the type of error is unclear, there is very little that you can do about it. It might be that the signal quality of the GSM network is too low but it is also possible that the GSM network rejects the messages or that there is an internal clash of incoming and outgoing messages that cause the problem. If the errors are sporadic then it is not really a big problem but if there are too many errors it is probably better to try a different GSM modem.

One thing you could try is to set the 'RebootBeforeInitialization' option to 'True' in the advanced settings of the GSM Modem Gateway properties. This sometimes solves this kind of problems but it does not always work properly with USB modems.

Regards, Henk

The error means that the GSM modem did not respond after Diafaan SMS Server tries to send the message. This is usually an indication that the modem is temporary busy, for instance when a message is received from the GSM network at the same time.

Sometimes it helps if you decrease the sending speed the messages, you can do that by increasing the 'SendDelayTime' property in the advanced settings of the GSM Modem Gateway. However, even with decreased send speed it is not unusual to get this error every now and then.

I am afraid that I am not able to give you advise about the firmware upgrade of your modem.

Regards, Henk

Hello Nick,

This type of behavior is usually an issue with the driver or firmware of the GSM modem, it might be necessary to update the driver software and firmware to the latest versions to solve this problem.

There are a couple of other options you can try first, most Huawei GSM modems have two serial ports and I have noticed that on some models the modem stops working after some time when it is connected to the "wrong" COM port. You can to connect Diafaan SMS Server to the other port and see what happens.

Another way to solve the same problem is to set the 'ModemInitializationBeginning' parameter in the advanced settings of the GSM Modem Gateway to 'AT^CURC=0'. This disables the diagnostics reporting on the serial port that seems to be the cause of the problem.

You can check if the link in your post has anything to do with your problem by setting the GSM Modem Gateway to 'Send only', this disables the +CMGL commands that causes the problems described in the link.

Regards. Henk