[Gradle] Try to adjust port finding logic to fix tests flakiness

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/BuildStatisticsWithKtorIT.kt

@@ -15,6 +15,7 @@ import io.ktor.response.*
 import io.ktor.routing.*
 import io.ktor.server.engine.*
 import io.ktor.server.netty.*
+import io.ktor.util.*
 import io.ktor.util.collections.*
 import org.gradle.util.GradleVersion
 import org.jetbrains.kotlin.gradle.plugin.stat.*
@@ -23,6 +24,7 @@ import org.jetbrains.kotlin.gradle.testbase.*
 import org.junit.jupiter.api.DisplayName
 import java.io.IOException
 import java.net.HttpURLConnection
+import java.net.InetSocketAddress
 import java.net.ServerSocket
 import java.net.URL
 import java.util.*
@@ -35,9 +37,14 @@ import kotlin.test.*
 class BuildStatisticsWithKtorIT : KGPBaseTest() {
 
     companion object {
+        private val portSelectLock = java.util.concurrent.locks.ReentrantLock()
+
         fun runWithKtorService(action: (Int) -> Unit) {
+            var server: ApplicationEngine? = null
+            try {
+                portSelectLock.lock()
                 val port = getEmptyPort().localPort
-            val server = embeddedServer(Netty, host = "localhost", port = port)
+                server = embeddedServer(Netty, host = "localhost", port = port)
                 {
                     val requests = ArrayBlockingQueue<String>(10)
 
@@ -64,8 +71,14 @@ class BuildStatisticsWithKtorIT : KGPBaseTest() {
                     }
                 }.start()
                 awaitInitialization(port)
+                portSelectLock.unlock()
                 action(port)
-            server.stop(1000, 1000)
+            } finally {
+                if (portSelectLock.isLocked) {
+                    portSelectLock.unlock()
+                }
+                server?.stop(1000, 1000)
+            }
         }
 
         private fun getEmptyPort(): ServerSocket {
@@ -73,7 +86,9 @@ class BuildStatisticsWithKtorIT : KGPBaseTest() {
             val endPort = 8180
             for (port in startPort..endPort) {
                 try {
-                    return ServerSocket(port).also {
+                    return ServerSocket().apply {
+                        bind(InetSocketAddress("localhost", port))
+                    }.also {
                         println("Use $port port")
                         it.close()
                     }