Why I cannot emulate a serial device (arduino or somethin else) using socat?

Question

I want to fake a device via a script and have the dart program to interface with it. Therefore, in my linux machine, I've run the following command to emulate a serial port:

socat PTY,link=./arduino-sim,raw,echo=0 PTY,link=./virtual-tty,raw,echo=0

And I've made a session via screen that will emulate the virtual device:

screen ./arduino-sim

Also, the dart programm itself is:

import 'package:libserialport/libserialport.dart';
import 'dart:typed_data';

void main(List<String> arguments) {
  final port = SerialPort("./virtual-tty");
  if (!port.openReadWrite()) {
    print(SerialPort.lastError);
  }

  port.write(Uint8List.fromList("Lorem Ipsum".codeUnits));

  final reader = SerialPortReader(port);
  reader.stream.listen((data) {
    print('received: $data');
  });
}

and both arduino-sim and virtual-tty have the common path with my dart project:

-rw-rw-r-- 1 pcmagas pcmagas 1038 Αυγ  17 13:36 analysis_options.yaml
lrwxrwxrwx 1 pcmagas pcmagas   10 Αυγ  17 14:59 arduino-sim -> /dev/pts/1
drwxrwxr-x 2 pcmagas pcmagas 4096 Αυγ  17 13:36 bin
-rw-rw-r-- 1 pcmagas pcmagas   29 Αυγ  17 13:36 CHANGELOG.md
drwxrwxr-x 2 pcmagas pcmagas 4096 Αυγ  17 13:36 lib
-rw-rw-r-- 1 pcmagas pcmagas 8063 Αυγ  17 14:13 pubspec.lock
-rw-rw-r-- 1 pcmagas pcmagas  276 Αυγ  17 13:37 pubspec.yaml
-rw-rw-r-- 1 pcmagas pcmagas  122 Αυγ  17 13:36 README.md
drwxrwxr-x 2 pcmagas pcmagas 4096 Αυγ  17 13:36 test
lrwxrwxrwx 1 pcmagas pcmagas   10 Αυγ  17 14:59 virtual-tty -> /dev/pts/3

But once I've run my project via dart run I get the following error:

art run
Building package executable... 
Built serial:serial.
SerialPortError: Success, errno = 0
Unhandled exception:
SerialPortError: Success, errno = 0

But if I plug an actual serial device (in my case an arduino Uno) and replace the line

final port = SerialPort("./virtual-tty");

with:

final port = SerialPort("/dev/ttyACM0");

Works fine:

Building package executable... 
Built serial:serial.
received: [82, 73, 78, 71, 13, 10, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10, 82, 73, 78, 71, 13, 10]
received: [82, 73, 78, 71, 13]

So why libserialport is unable tyo use virtual serial port;