Fixed bug with wrong line numbers in error messages. Some examples refactoring and bug fixes. (0.39.15)

examples/blocking/tcp_echo_server.fun

@@ -0,0 +1,37 @@
+#!/usr/bin/env fun
+
+/*
+ * This file is part of the Fun programming language.
+ * https://fun-lang.xyz/
+ *
+ * Copyright 2025 Johannes Findeisen <you@hanez.org>
+ * Licensed under the terms of the Apache-2.0 license.
+ * https://opensource.org/license/apache-2-0
+ *
+ * Added: 2025-10-13
+ */
+
+// Simple TCP echo server using built-in socket ops.
+// Listens on localhost:12345 and echoes a single line/request back to each client.
+
+port = 12345
+backlog = 16
+
+listen_fd = tcp_listen(port, backlog)
+if (listen_fd <= 0)
+  print("tcp_listen failed")
+  exit(1)
+
+print("Echo server listening on port " + to_string(port))
+
+while (true)
+  client = tcp_accept(listen_fd)
+  if (client > 0)
+    data = sock_recv(client, 4096)
+    if (len(data) > 0)
+      // Echo back exactly what we received
+      sock_send(client, data)
+    sock_close(client)
+
+// Not reached in this example, but here for completeness
+sock_close(listen_fd)