Though UCP (Universal Computer Protocol) is considered a legacy protocol for sending SMS, there are still cases - especially with European mobile operators - where you're required to comply with it.
In one of our projects, we had to implement UCP ourselves, as no actively maintained Java libraries were available. Fortunately, UCP is a text-based protocol, which makes it relatively simple to work with — but only if you handle the details precisely.
A typical UCP message looks like this:
02/51/O/51/username/password/123456/0044170000000/Hello World//////////1/7
The trick? Carefully follow the specific field formats, character escaping rules, and checksum logic. When implemented properly, UCP still gets the job done - even in a modern system.