Issue: Incoming SMS message with no sender (MultiTech rCell modem)

Issue: Incoming SMS message with no sender (MultiTech rCell modem)

This issue can potentially affect TopView v7.2 and earlier users who implement SMS notification using the MultiTech rCell 100 modem. This issue is only related to incoming SMS messages (e.g. alarm acknowledge).

Background
When TopView pulls incoming SMS messages from the modem, it logs each message, processes the contents of each message, then deletes the messages from the modem.

Issue
If an incoming message has no sender (the phone number of the sender is empty/Null), TopView logs an exception to the application  log but does not delete the message from the modem.

The same message, and any addition incoming messages from valid senders, are processed again with the same result - logging of the exception but no removal of the messages from modem's SMS inbox. Messages with valid senders may receive an SMS message from TopView with the message processing results each time the inbox is polled.

At the time of this article, this issue has only occurred with one customer, but it occurred multiple times.
Incoming SMS messages should always have a valid sender/phone number but with this customer it was possible to have an incoming SMS message with no sender/number.
Symptoms
  1. Application log: the same two error messages are logged each time the modem inbox is polled (messageid will be a number):
    SMS/Messaging error processing incoming message #(messageid) : Object reference not set to an instance of an object.
    SMS/Messaging incoming : Error in incoming message processing thread: Object reference not set to an instance of an object. 
  2. Admin tools: watching the real time incoming SMS screen, the same number of messages are processed each time the modem is polled indicating that the messages are not being removed from the modem after processing.
  3. Modem Web UI: the modem SMS inbox has one or more messages with no sender
Resolution
  1. Patch for TopView v7.2: the download page for TopView v7.2 has a patch that can downloaded and applied. Customers with earlier versions of TopView will need to upgrade to v7.2 before applying the patch.
  2. Temporary resolution: log into the Web UI of the modem and delete the messages from the SMS inbox. This will resolve the issue unless/until another incoming message appears with no sender/phone number.

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