Sending SMS in Kotlin: API Library

Sending SMS in Kotlin: API Library for Quick Integration

In modern web development, the ability to programmatically send SMS messages remains a sought-after feature — from two-factor authentication to order status notifications. If you use Kotlin for the server side (Ktor, Spring Boot) or a mobile application (Android), you will need a reliable tool for working with SMS providers. In this article, we will look at the API library for sending SMS in Kotlin, its capabilities, integration examples, and best practices.

What is an API Library for Sending SMS?

An API library is a set of classes and functions that abstracts working with HTTP requests to the SMS provider's server. Instead of manually forming URLs, headers, and parsing JSON, you call simple Kotlin methods: sendSms(phone, message). The library handles authentication, serialization, retries on network errors, and response processing.

Main Features of the Library

Simple SMS sending — specifying the recipient's number, text, and optionally the sender name (alpha-name).
Batch sending — sending one message to a list of numbers.
Status checking — obtaining delivery information (delivered, queued, error).
Support for different providers — Twilio, Vonage (Nexmo), SMSC.ru, Smsc.ua, and others.
Asynchrony — all methods return suspend functions or Deferred for coroutines.
Logging and error handling — built-in mechanisms for debugging.

Installation and Setup

The library is distributed via Maven Central or JitPack. Add the dependency to build.gradle.kts:

// build.gradle.kts (for Gradle Kotlin DSL)dependencies {    implementation("com.example:sms-api:1.0.0")    // if using Ktor Client    implementation("io.ktor:ktor-client-core:2.3.0")    implementation("io.ktor:ktor-client-okhttp:2.3.0")}

For Android, also add the internet permission in AndroidManifest.xml.

Basic Example of Sending SMS

Let's look at a minimal example of sending a single message via the SMSC.ru provider (similar for others).

import com.example.smsapi.SmsClientimport com.example.smsapi.model.SmsRequestimport com.example.smsapi.model.SmsResponse

suspend fun sendSingleSms() {    // Create a client with credentials    val client = SmsClient.create(        login = "your_login",        password = "your_password",        provider = SmsProvider.SMSC    )

    // Form the request    val request = SmsRequest(        phone = "+71234567890",        message = "Your confirmation code: 1234",        sender = "MyApp" // alpha-name, if supported    )

    // Send and receive the response    val response: SmsResponse = client.send(request)

    when (response.status) {        SmsStatus.SUCCESS -> println("SMS sent, ID: ${response.id}")        SmsStatus.ERROR -> println("Error: ${response.errorMessage}")        else -> println("Unknown status")    }}

Batch Sending

To send one message to multiple numbers, use the sendBatch method:

val phones = listOf("+71234567890", "+70987654321", "+71112223344")val batchRequest = BatchSmsRequest(    phones = phones,    message = "Dear customers, the promotion has been extended until Friday!",    sender = "ShopBot")

val batchResponse = client.sendBatch(batchRequest)batchResponse.results.forEach { result ->    println("Phone: ${result.phone}, status: ${result.status}")}