I have playing with SMPP messaging platform to send an A2P SMS. It is a new area that I learnt a lot to building a messaging platform. There are some issue or problem that I hit the wall, such as error message CONCATENATED_MESSAGE_TOO_LONG.
After digest some information, it seems the content is not properly set so the message cannot send successfully.
After investigating logs of the reported messages, I noticed that they were submitted with ISO data coding (data_coding:0x03) and a 7-byte UDH, in which case the character limit is 132. Considering the first message contains 153 messages, they failed with status “CONCATENATED_MESSAGE_TOO_LONG”.
I will include a couple of example scenarios to show other character limits as well:
Example 1 – GSM-7 data coding, 6-byte UDH:
maxCharactersCount = 153
Example 2 – GSM-7 data coding, 7-byte UDH:
maxCharactersCount = 152
Example 3 – ISO data coding, 6-byte UDH:
maxCharactersCount = 133
Example 4 – ISO data coding, 7-byte UDH:
maxCharactersCount = 132
With this in mind, in order to successfully deliver messages with your current setup, the maximum amount of characters you can use per message is 132. Or you can adjust your setup in line with the above information.