Add TCP server example and refactor script execution flow

examples/tcpserver.lyng

@@ -0,0 +1,21 @@
+import lyng.buffer
+import lyng.io.net
+
+val server = Net.tcpListen(0, "127.0.0.1")
+val port = server.localAddress().port
+val accepted = launch {
+    val client = server.accept()
+    val line = (client.read(4) as Buffer).decodeUtf8()
+    client.writeUtf8("echo:" + line)
+    client.flush()
+    client.close()
+    server.close()
+    line
+}
+
+val socket = Net.tcpConnect("127.0.0.1", port)
+socket.writeUtf8("ping")
+socket.flush()
+val reply = (socket.read(16) as Buffer).decodeUtf8()
+socket.close()
+println("${accepted.await()}: $reply")

lyng/src/commonMain/kotlin/Common.kt

@@ -27,7 +27,7 @@ import com.github.ajalt.clikt.parameters.arguments.optional
 import com.github.ajalt.clikt.parameters.options.flag
 import com.github.ajalt.clikt.parameters.options.option
 import kotlinx.coroutines.runBlocking
-import net.sergeych.lyng.Compiler
+import net.sergeych.lyng.EvalSession
 import net.sergeych.lyng.LyngVersion
 import net.sergeych.lyng.Script
 import net.sergeych.lyng.ScriptError
@@ -216,12 +216,7 @@ private class Lyng(val launcher: (suspend () -> Unit) -> Unit) : CliktCommand()
                     launcher {
                         // there is no script name, it is a first argument instead:
                         processErrors {
-                            val script = Compiler.compileWithResolution(
-                                Source("<eval>", execute!!),
-                                baseScope.currentImportProvider,
-                                seedScope = baseScope
-                            )
-                            script.execute(baseScope)
+                            executeSource(Source("<eval>", execute!!))
                         }
                     }
                 }
@@ -247,6 +242,15 @@ fun executeFileWithArgs(fileName: String, args: List<String>) {
     }
 }
 
+suspend fun executeSource(source: Source) {
+    val session = EvalSession(baseScopeDefer.await())
+    try {
+        session.eval(source)
+    } finally {
+        session.cancelAndJoin()
+    }
+}
+
 suspend fun executeFile(fileName: String) {
     var text = FileSystem.SYSTEM.source(fileName.toPath()).use { fileSource ->
         fileSource.buffer().use { bs ->
@@ -259,13 +263,7 @@ suspend fun executeFile(fileName: String) {
         text = text.substring(pos + 1)
     }
     processErrors {
-        val scope = baseScopeDefer.await()
-        val script = Compiler.compileWithResolution(
-            Source(fileName, text),
-            scope.currentImportProvider,
-            seedScope = scope
-        )
-        script.execute(scope)
+        executeSource(Source(fileName, text))
     }
 }
 

lyngio/src/commonTest/kotlin/net/sergeych/lyng/io/net/LyngNetTcpServerExampleTest.kt

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package net.sergeych.lyng.io.net
+
+import kotlinx.coroutines.runBlocking
+import kotlinx.coroutines.withTimeout
+import net.sergeych.lyng.Compiler
+import net.sergeych.lyng.Script
+import net.sergeych.lyngio.net.getSystemNetEngine
+import net.sergeych.lyngio.net.security.PermitAllNetAccessPolicy
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class LyngNetTcpServerExampleTest {
+
+    @Test
+    fun tcpServerExampleRoundTripsOverLoopback() = runBlocking {
+        val engine = getSystemNetEngine()
+        if (!engine.isSupported || !engine.isTcpAvailable || !engine.isTcpServerAvailable) return@runBlocking
+
+        val scope = Script.newScope()
+        createNetModule(PermitAllNetAccessPolicy, scope)
+
+        val code = """
+            import lyng.buffer
+            import lyng.io.net
+
+            val server = Net.tcpListen(0, "127.0.0.1")
+            val port = server.localAddress().port
+            val accepted = launch {
+                val client = server.accept()
+                val line = (client.read(4) as Buffer).decodeUtf8()
+                client.writeUtf8("echo:" + line)
+                client.flush()
+                client.close()
+                server.close()
+                line
+            }
+
+            val socket = Net.tcpConnect("127.0.0.1", port)
+            socket.writeUtf8("ping")
+            socket.flush()
+            val reply = (socket.read(16) as Buffer).decodeUtf8()
+            socket.close()
+            "${'$'}{accepted.await()}: ${'$'}reply"
+        """.trimIndent()
+
+        val result = withTimeout(5_000) {
+            Compiler.compile(code).execute(scope).inspect(scope)
+        }
+
+        assertEquals("\"ping: echo:ping\"", result)
+    }
+}