chore: ktor tcp server test sample

Author: sureshg

backend/jvm/src/test/kotlin/dev/suresh/KtorTests.kt

@@ -0,0 +1,60 @@
+@file:OptIn(DelicateCoroutinesApi::class)
+
+package dev.suresh
+
+import io.ktor.network.selector.SelectorManager
+import io.ktor.network.sockets.aSocket
+import io.ktor.network.sockets.awaitClosed
+import io.ktor.network.sockets.openReadChannel
+import io.ktor.network.sockets.openWriteChannel
+import java.net.InetSocketAddress
+import java.time.Duration
+import kotlin.concurrent.thread
+import kotlinx.coroutines.DelicateCoroutinesApi
+import kotlinx.coroutines.async
+import kotlinx.coroutines.newSingleThreadContext
+import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.test.runTest
+import org.junit.jupiter.api.Assertions.assertEquals
+
+class KtorTests {
+
+  // @Test
+  fun tcpServer() = runTest {
+    val address = InetSocketAddress.createUnresolved("localhost", 9999)
+    val selectorManager = SelectorManager(newSingleThreadContext("TcpRunner"))
+
+    aSocket(selectorManager).tcp().bind(address.hostName, address.port).use { serverSocket ->
+      println("TCP server is listening at ${serverSocket.localAddress}")
+
+      repeat(5_000) {
+        // If the thread hangs, this won't complete within the timeout
+        println("Awaiting new connection")
+        val socketAsync = async { serverSocket.accept() }
+        aSocket(selectorManager).tcp().connect(address.hostName, address.port)
+        val socket = socketAsync.await()
+        println("Accepted connection from ${socket.remoteAddress}, $socket")
+
+        println("Closing connection to ${socket.remoteAddress}")
+
+        val thread = thread {
+          val readChannel = socket.openReadChannel()
+          val writeChannel = socket.openWriteChannel(autoFlush = true)
+
+          socket.close()
+          runBlocking {
+            // With manual flushAndClose of the WriteChannel, 3.2.0 works.
+            //
+            // Note: This is _usually_ not needed, only a small percentage of connections
+            //       fail to close properly without it.
+            //                                writeChannel.flushAndClose()
+            socket.awaitClosed()
+          }
+        }
+
+        thread.join(Duration.ofMillis(500))
+        assertEquals(Thread.State.TERMINATED, thread.state)
+      }
+    }
+  }
+}