Serial Tap over SSH

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The Serial Tap over SSH plugin extends the power of the IO Ninja Serial Tap to remote Linux devices, enabling monitoring of serial ports on machines like headless Raspberry Pi boards.

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 the Hardware Client

The Serial Tap over SSH plugin uses the IO Ninja Hardware Client (ioninja-hwc).

This hardware client needs to be installed and configured on the remote machine.

Note

See Installing the Hardware Client for instructions.

Serial SSH’ing into your Linux Machine with IO Ninja

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

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

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

Note

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

Note

Before capturing, you should select the proper baud rate (and other serial parameters).

Click the “Capture” button to the right of the “Address:” field to initiate a connection.

Note

You will be prompted for SSH credentials.

Monitor your Serial Communications as Usual

See all communications in the Ninja Scroll Engine.

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
Baud rate	The serial baud rate.	38400 bps
Data bits	Serial data bit count (word size). See available options.	8 bits
Parity	Serial parity check type. See available options.	None
Stop bits	Serial stop bit count. See available options.	1 bit
Flip DTE/DCE	Flip logical sides of the tap cable. All serial lines can be split into `IN`/`OUT` pairs. The `TX` line for one side of the link is the `RX` for the other side, the same goes for `DTR`-`RTS` and `RTS`-`CTS`. When “Flip DTE/DCE” is enabled, those pairs are flipped. This allows you to view the communication from the perspective of any side of the link, without physical rewiring.	False
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

Data Bit Options

Option
5 bits
6 bits
7 bits
8 bits

Parity Options

Option	Description
None	No parity bit is used
Odd	Odd parity (parity bit is set when the number of logical ones in the UART frame is odd).
Even	Even parity (parity bit is set when the number of logical ones in the UART frame is even).
Mark	Parity bit is present and always set.
Space	Parity bit is present and always clear.

Stop Bit Options

Option
1 bit
1.5 bits
2 bits