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It depends how often this error occurs and what the root cause of the error is. When the modem encounters an error, Diafaan SMS Server restarts the GSM Modem Gateway and that is what you see in the event log. A possible error can be that the modem and network have a temporary communication problem, this is a common problem with GSM modems that are connected to a busy network or are placed in a location with low signal strength. Some combinations of modems and mobile networks generate more of these errors than others but it is not uncommon to see an error for every 20 messages or so that you send.

Since you are using the GSM modem (or an Android phone ) over an Internet or WiFi connection, it is also possible that the internet connection to your modem is unreliable. The Internet connection to the modem does not have to be fast but it should be consistently reliable.

If you send a communication log of the modem to dms@diafaan.com I may be able to tell the exact cause of the error (please include the serial number of your license in the email).

Regards, Henk

There is not much you can do, either the delivery reports work or they don't. An issue with the number format difference between the message and the receipt is the only reason that Diafaan SMS Server would not process a received delivery report correctly but that does not seem the case in your situation.

There could be two reasons why the delivery reports sometimes stop working:

- Your mobile operator might not always send delivery reports. I have seen this happen when the SMS traffic for a modem was very high.

- It is also possible that the Android phone does not always forward delivery reports to the GSM Modem Emulator app, I have not received any other reports about this but it might be an issue that is specific to your phone.

Regards, Henk

When Diafaan SMS Server does not receive a response to the HTTP callback from the web server within a specific time, it triggers a timeout and sends the HTTP callback again one time, with the extra 'callback_retries=1' parameter to let the web server know that this is a repeated HTTP callback.

It is important to keep the response time for the HTTP callback call as low as possible. It is sometimes difficult to get a consistent low response time, especially when you use a remote web server or a PHP or ASP.NET script with a database lookup. A consistent response time lower than 50 milliseconds is ideal.

You can increase the timeout value for the HTTP callbacks in the settings of Diafaan SMS Server (menu options 'Actions-Options-HTTP callbacks'). However, keep in mind that the HTTP call blocks other actions in the gateway or connector during the call. If the HTTP callbacks take too long, it can slow down the message processing within the gateway or connector considerably.

Regards, Henk

The GSM Modem Gateway has a 'SendLimit' option to limit the number of messages that is sent in a specific time period. You can find this option in the advanced settings of the GSM Modem Gateway properties.

This option allows a maximum of messages per whole hour, day, week or month. To limit the number of messages to 175 per day you can set the value to '175D'. Please note that all messages send attempts are counted in the limit, also when the GSM modem returns an error when the message cannot be sent. You can set the 'SendLimitErrorCodeExceptionList' to prevent counting specific errors (or all errors) in the message limit.

When the message limit is reached, the GSM Modem Gateway pauses until the next whole hour, day, week or month.

Regards, Henk

For messages sent with a GSM modem, the 'message_id' parameter is not guaranteed to be unique. The message ID is a combination of the gateway ID of the gateway that sent the message, the destination number of the message and a reference number from the GSM modem. Since the reference number from the modem is a number between 0 an 255, it is reused by the GSM modem after sending 255 messages.

If you match the status update (with status code 201) with the last record that has status code 200 and the same message ID, you are reasonably safe. Diafaan SMS Server uses the same method to match the status update with the original message in the send log.

Messages that are sent with the SMPP Gateway get a unique message ID from the SMPP server, in that case the match on the message_id value is always reliable.

Regards, Henk