Simple code to get your public ip address

Ip.kt

import IpAddress.Companion.IP_END
import IpAddress.Companion.IP_SEGMENT_SIZE
import IpAddress.Companion.IP_START
import kotlinx.coroutines.experimental.runBlocking
import java.net.URL

/**
 * Ipfy
 */
data class IpAddress(private val segment1: Int,
                     private val segment2: Int,
                     private val segment3: Int,
                     private val segment4: Int) {
    companion object {
        val SEGMENT_SEPARATOR = "."
        val IP_SEGMENT_SIZE = 4

        val CLASS_A_START = 0
        val CLASS_A_END = 127

        val CLASS_B_START = 128
        val CLASS_B_END = 191

        val CLASS_C_START = 192
        val CLASS_C_END = 223

        val IP_START = 0
        val IP_END = 255
    }

    val type: Type = when (segment1) {
        in CLASS_A_START..CLASS_A_END -> Type.CLASS_A
        in CLASS_B_START..CLASS_B_END -> Type.CLASS_B
        in CLASS_C_START..CLASS_C_END -> Type.CLASS_C
        else -> {
            throw InvalidIpAddressException()
        }
    }

    enum class Type {
        CLASS_A, CLASS_B, CLASS_C
    }

    override fun toString(): String = "$segment1.$segment2.$segment3.$segment4"
}

class InvalidIpAddressException(message: String = "Invalid IP, the format must be XXX.XXX.XXX.XXX") : Exception(message)

fun stringToIp(text: String): IpAddress {
    val segments = text.split(IpAddress.SEGMENT_SEPARATOR)
    val invalidSegments = segments.filter { it.toIntOrNull() == null || it.toInt() !in IP_START..IP_END }.count()

    if (invalidSegments > 0 || segments.size != IP_SEGMENT_SIZE) {
        throw InvalidIpAddressException()
    }

    return IpAddress(segments[0].toInt(), segments[1].toInt(), segments[2].toInt(), segments[3].toInt())
}

suspend fun callIpfy(): IpAddress = stringToIp(URL("https://api.ipify.org?format=text").readText())

fun main(args: Array<String>) {
    runBlocking {
        val ip = callIpfy()
        println(ip)
        when (ip.type) {
            IpAddress.Type.CLASS_A -> println("class A!!")
            IpAddress.Type.CLASS_B -> println("class B!!")
            IpAddress.Type.CLASS_C -> println("class C!!")
        }
    }
}