I need to work with ISO8583 messages to exchange packages between financial entities.
I was studying how this protocol works, however, I have not been able to find whole examples of how this message should be put together.
I know the structure of the message: [HEADERS] [MTI] [BITMAP] [DATA ELEMENT]
I know how to build the MTI, I know how to build the BITMAP. I can not find clear examples of how to include the headers and the data element (DE). Each field of the DE has a definition of length and type of data admitted, which can be fixed or variable. As I understand the length is specified at the beginning with the first 2 bytes of the value of the field.
But if it is variable, is it also specified? If it is variable, and the entire length is not occupied, are the spaces left blank?
Likewise, from .NET there are several packages available from Nuget but they lack documentation for their use, if someone knows and wishes to share some development I would appreciate it.
I hope you understand my doubts, thanks in advance.