How can I set up virtual serial ports (Linux null modem emulator) using tty0tty

tty serial-port emulation

51,750

Installation

Download the tty0tty package from one of these sources:
- http://sourceforge.net/projects/tty0tty/files/
- clone the repo https://github.com/freemed/tty0tty:
```
git clone https://github.com/freemed/tty0tty
```
Extract it:
```
tar xf tty0tty-1.2.tgz
```
Build the kernel module from provided source:
```
 cd tty0tty-1.2/module
 make
```

Copy the new kernel module into the kernel modules directory:

 sudo cp tty0tty.ko /lib/modules/$(uname -r)/kernel/drivers/misc/

Load the module:
```
 sudo depmod
 sudo modprobe tty0tty
```
You should see new serial ports in /dev/ (ls /dev/tnt*)
Give appropriate permissions to the new serial ports:
```
 sudo chmod 666 /dev/tnt*
```

You can now access the serial ports as /dev/tnt0 (1,2,3,4 etc) Note that the consecutive ports are interconnected. For example, /dev/tnt0 and /dev/tnt1 are connected as if using a direct cable.

Persisting across boots

Edit the file /etc/modules (Debian) or /etc/modules.conf

sudo nano /etc/modules.conf

and add the following line:

tty0tty

Warning

Note that this method will not make the module persist over kernel updates so if you ever update your kernel, make sure you build tty0tty again repeat the process.

If you don't move the module on every kernel update systemctl --failed will return that service systemd-modules-load.service ended "failed". Also on journalctl -xe | grep "Failed to find".

51,750

yuva

Updated on September 18, 2022

Comments

yuva almost 2 years
I want to set up a virtual serial port emulator in Linux. I want the ports to be permanent, so that I can use them every time I restart. I tried using socat for that purpose in this way,
```
socat -d -d pty,raw,echo=0 pty,raw,echo=0
```
But I often get "port busy" issues during the usage of these VSPs (Virtual Serial Ports) in my test programs. Also, I find it hard to create permanent/persistent VSPs.

I now want to try out tty0tty for my purposes. But I have found little documentation on how to use it. Can anyone enlighten me on this? Please do comment if there are any solutions for socat as well.
yuva over 9 years

Thanks mate, that worked pretty fine. Wasn't being able to find this anywhere else.
Ruraj over 9 years

:) glad I could help!
Foad over 5 years

Does tty0tty also support mac OS?
Ruraj almost 5 years

You might be able to build it and load the kernel module using kextutil, but I have never tried it!
master_clown almost 5 years

Gorgeous explanation. Every point is nice and neat. Always glad to see such responses