Serial Monitor over SSH

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The Serial Monitor over SSH plugin allows you to monitor all the serial ports activity initiated by applications on a remote machine. It’s just like Serial Monitor, but instead of monitoring a locally attached serial port, you will see requests from applications to serial ports of another machine.

Basic Setup

Prerequisites

Enabling SSH

On most Linux machines, SSH is enabled by default. However, if it is not, you will need to enable it.

On Raspbian and many other popular distros, you can perform the following command:

systemctl enable --now sshd

For other Linux distributions, please refer to their documentation.

Installing Tibbo Device Monitor

For the Serial Monitor over SSH plugin to function properly, the target machine must have the Device Monitor (tdevmon) service version 3.3.2 or above installed and available via PATH. Then it’s possible to establish an SSH connection to the target machine, start the tdevmon process in machine interface mode remotely and then read and decode notifications from tdevmon over SSH.

See Installation of Tibbo Device Monitor on Linux for full instructions.

Identifying the Port

Later on, you will need to know what port your serial device is connected to.

On your Linux machine, perform the following command:

ioninja-hwc --ser-enum

The terminal should print a new line, similar to this:

/dev/ttyUSB0

This string of text will be entered into IO Ninja later, so make a note of it.

Alternatively, you can perform the following command:

dmesg --follow | grep -i tty

While the process is running, reconnect your device.

The terminal should print a new line, similar to this:

usb 1‑1.1: FIDI USB Serial Device converter now attached to ttyUSB0

In this case, the output indicates the port used is ttyUSB0, but yours may be different.

Serial Monitor SSH’ing into your Linux Machine with IO Ninja

In IO Ninja, click “New Session” and select a new “Serial Monitor over SSH” session.

Type the host address of your remote Linux machine into the “Address:” field.

Type the port we identified earlier into the “Port:” field, prefixed by /dev/.

Click the “Open” button to the right of the “Port:” field to initiate a connection.

You will be prompted for SSH credentials.

Adjust settings as needed via the “Settings” button (see “Settings” section below for details).

Some of these settings are also available in the “Control” pane for easy access.

Monitor your Serial Device as Usual

See all communications in the Ninja Scroll Engine.

Add a layer such as Modbus Analyzer to make the most out of Modbus communications.

Settings

Setting	Description	Default
Remote address	Remote address to connect to. Can be specified via IPv4 (`127.0.0.1`), IPv6 (`::1`), or a domain name (`localhost`). Remote address can be suffixed with the remote port after a colon, e.g. `ioninja.com:443`.
Remote port (default)	Remote port to connect to in cases when a port is not explicitly specified in Remote address.	80
Use local address	Bind socket to the specified local address.	False
Adapter	Local network adapter to bind to. Pick one from the list of installed network adapters (or bind to all installed `IP4` or all `IP6` adapters at once).	Auto
Local port	Local port to bind to. Setting this to `0` auto-selects an available port.	8080
Reuse address	Allow multiple sockets to share the same local address. Maps to the `SO_REUSEADDR` socket option. Please note, the support and details of implementation for this option are highly platform-specific.	False
TCP Nagle algorithm	Delay transmission to reduce the number of small TCP packets. Maps to the `TCP_NODELAY` socket option.	False
TCP reset	Drop TCP connections abruptly with a TCP RST packet. Maps to the `SO_LINGER` socket option.	False
TCP keep-alives	Detect connection loss with TCP keep-alive probes. Maps to the `TCP_KEEPALIVE` socket option.	False
User name	User name for SSH authentication.
User authentication	SSH authentication method (password or private key)	Password
Private key file	Private key file for SSH authentication (PEM format).
Remember last password	Re-use the last entered password during subsequent connect attempts.	True
Read block size (B)	The size of each individual read block submitted to the underlying transport.	4KB
RX buffer size (B)	The full size of the incoming data (RX) buffer. Affects read throughput.	16KB
TX buffer size (B)	The full size of the outbound data (TX) buffer. Affects write throughput..	16KB
Keep read block size	Don’t merge read blocks in RX buffer. Incoming data blocks coming in quick succession can be merged together so that IO Ninja writes them to log as a whole. When this option is set to `True`, blocks are written to the log without merging, i.e., exactly as they are received from the underlying transport..	False
Keep write block size	Don’t merge write blocks in TX buffer. Outbound data blocks sent in quick succession can be merged together before submission to the underlying transport. When this option is set to `True`, blocks are submitted to the transport without merging, i.e., exactly as they are sent by the Transmit or Script panes..	False
RX buffer full notifications	Toggle warnings in log about the incoming data (RX) buffer getting full.	False
Serial setting changes	Toggle notifications about serial setting (baud rate, data size, parity, stop bits, flow control) changes in the log.	on
DTR/RTS changes	Toggle notifications about control line (`DTR`, `RTS`) changes in the log.	on
DSR/CTS/DCD/RI changes	Toggle notifications about status line (`DSR`, `CTS`, `DCD`, `RI`) changes in the log.	on
Serial line errors	Toggle warning about serial line errors (`PARITY`, `FRAMING` and `BREAK`) in the log.	on

FAQ (Frequently Asked Questions)

1. Can I timestamp each line of serial data based on carriage return (CR) rather than fixed-size blocks, and export it for use in external software?

IO Ninja timestamps entire data blocks as they are received from the operating system, not individual bytes. Since bytes within a block arrive in quick succession, the block timestamp provides a reliable indication of when the data was received. Although you cannot assign timestamps to each CR-terminated line directly, the existing timestamps offer millisecond-level accuracy and can be exported for use in test or simulation systems.