Using ser2net to remotely access a serial terminal or port

Tutorials
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In this tutorial, we will guide you through the process of setting up and using ser2net to remotely access a serial terminal on a Linux computer. This setup is particularly useful for managing embedded systems, IoT devices, or any device that communicates over a serial interface.

Prerequisites

  • A Linux computer with a serial port (e.g., /dev/ttyS0 or /dev/ttyUSB0).
  • Basic knowledge of Linux command-line operations.
  • We will assume a Ubuntu/Debian style system, instructions might need adaptation for other distributions.

Installation

Installing Ser2net

ser2net is a simple TCP-to-serial port redirector. To install ser2net, use the following command:

sudo apt-get install ser2net

Getting started

ser2net uses a configuration file to define the mappings. This configuration file can hold a large number of exposed connections, but we will stick to the minimal case of one here.

Create a Configuration File

Create the configuration file for ser2net. The expected location is /etc/ser2net/ser2net.yaml.

sudo nano /etc/ser2net/ser2net.yaml

Add Configuration Entries

Add entries to the configuration file to define the mappings. For example:

connection: &ttyUSB0
  accepter: tcp,2000
  options:
    banner: mybox - ttyUSB0
  connector: serialdev,/dev/ttyUSB0,115200n81,local

This entry maps TCP port 2000 to /dev/ttyUSB0 with a baud rate of 115200, 8 data bits, no parity, and 1 stop bit. The banner option displays a message when a connection is established.

Test ser2net

Start the ser2net service:

sudo ser2net -d

This starts ser2net in non-detached mode, so you can see eventual error messages. This is particularly helpful when working on the configuration file.

From a remote machine, use telnet to connect to the exposed serial port:

telnet <linux_computer_ip or hostname> 2000

You should see the configured banner message and be able to interact with the serial port. telnet can be closed by entering command mode with Ctrl-] and then issueing quit.

Permanently enable ser2net

Once you are done with setting the correct configuration up, you can have the ser2net service started automatically. Enable ser2net to start on boot:

sudo systemctl enable ser2net

And if you want to use it right away without rebooting, you can also start the service with:

sudo systemctl start ser2net

Accessing the serial terminal remotely

From a remote machine, use a terminal emulator like telnet to connect to the Linux computer:

telnet <linux_computer_ip or hostname> 2000

Alternative tools are nc or socat, depending on the specific use case.

Further Resources

By following this tutorial, you should be able to set up and use ser2net to remotely access a serial terminal on a Linux computer. This setup provides a flexible and powerful way to manage serial communications over a network.

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