I am currently supporting an SMS application for CIMD and sometimes i get a strange behaviour from the smsc. This has to do with the fact that when i start the application and send the login message with sequence 1 i get a nack response with sequence 3 from the SMSC. In addition to this , i sometimes get a nack response from the SMSC with an incorect sequence, e.g. i send sequence 5 and get a nack with 7. If there was something wrong with the messages that i sent then i should get a nack response of the same sequence which i sent but i do not. Instead i get a nack response with the next sequence. The response for the message that i originally sent never comes and surprisingly all the other messages that i subsequently send work fine.
Remember that before i get the response from the smsc i do not send any other message, just to be sure that this issue is not related to incorrect windowing usage.
It is really very strange because it happens very rarely and without any changes made by me, prior to running the application.
I would appreciate any thoughts.