# Introduction The SMSC service is designed to send SMS messages and Flashcall. The service operates on the basis of the SMPP 3.4 protocol SMPP protocol requires a client. For the most popular programming languages, there are freely distributed SMPP clients implemented as specialized libraries. The following sections provide instructions and recommendations for working with SMSC. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://smsc.revicom.ltd/how-to-work-with-smsc/readme.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.