c# open serial port created by socat - virtual-serial-port

Question

Create two virtual serial ports
socat -d -d -d PTY,b115200,raw,echo=0,crnl,link=/home/user/ttyS110 PTY,b115200,raw,echo=0,crnl,link=/home/user/ttyS111
cat /home/user/ttyS110
echo "hello" > /home/user/ttyS111
Works!
Try open:
using System;
using System.IO.Ports;
namespace qqq
{
class MainClass
{
public static void Main (string[] args)
{
SerialPort fSerialPort = new SerialPort();
fSerialPort.PortName = "/home/user/ttyS111";
fSerialPort.BaudRate = 115200;
fSerialPort.Parity = Parity.None;
fSerialPort.DataBits = 8;
fSerialPort.StopBits = StopBits.One;
fSerialPort.ReadTimeout = 500;
fSerialPort.WriteTimeout = 500;
try
{
fSerialPort.Open();
Console.WriteLine("Open port");
}
catch (Exception e)
{
Console.WriteLine("Open port ERROR! " + e.Message);
}
}
}
}
Catch exception "Invalid argument".
How open virtual port from c# (Mono)?

Answer 1

It would seem this has something to do with socat not emulating a serial port correctly. All I could find that was of help was the info below, which relates to a USB to Serial adapter, but I'm guessing socat is behaving the same way.
When opening the serial port, System.IO.Ports.SerialPort indirectly
calls SetSignal, which calls the TIOCMGET ioctl, which, as it happens,
ISN'T IMPLEMENTED in the mos7720 driver!
http://advogato.org/person/tripp/diary/18.html