Features

Features for protocol tracing, device bring-up and field diagnostics.

Scan the capabilities by real debugging jobs: connect ports, inspect bytes, validate protocols and keep field-service records aligned.

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Windows, macOS and Linux Version 6.6.4

Serial Port Utility desktop workspace

Real interface from Serial Port Utility.

Connect

Five ways to reach a device, up to sixteen at a time.

Serial, TCP client and server, UDP client, server and multicast, plus a remote serial port over RFC 2217 — every mode opens in the same window, so a gateway and the port behind it are never two separate tools.

  • Up to 16 connections on screen, in four layouts
  • Custom baud rates beyond the presets
  • Data bits, parity, stop bits and flow control
  • TCP server (multi-client) and TCP client
  • UDP client, server and multicast (UDP group)
  • RFC 2217 serial control, as a server or on a remote port
Serial connection parameters TCP and UDP debugging RFC 2217 server RFC 2217 client
The Serial Port Utility workspace with several connections open side by side

Real interface from Serial Port Utility.

Inspect

Read the bytes the device actually sent.

Switch between text and hex, pick the encoding each connection speaks, and timestamp every line so a capture taken tonight still answers questions next week.

  • Switch between ASCII and Hex
  • Per-connection send and receive encodings: UTF-8, GBK, GB18030, Big5, Shift-JIS and more
  • Configurable time formats
  • Rotate logs by size or time
  • TX/RX and control-line lamps show the link is alive
Text, Hex and encodings Logs and long-running capture Indicator lamps and control lines
The encoding selector beside Text and Hex in the Receive and Send settings

Real interface from Serial Port Utility.

Compose

Build a frame once, then replay it.

Keep the frames you send often in a reusable list, let the checksum be appended for you, and hand Modbus RTU frames to the request builder instead of counting bytes by hand.

  • Modbus request builder in the Tools menu
  • CRC-8/16/32 family: MODBUS, USB, CCITT, XMODEM and more
  • Custom CRC parameters, fed straight into the send frame
  • Auto-append the checksum when sending
  • Loop send at a fixed interval, or line by line
Automatic send and command lists CRC and Modbus checks
The Modbus request builder assembling an RTU frame

Real interface from Serial Port Utility.

Bridge

Turn this machine into a serial device server.

Link two connections and a program on the network reads and writes the local serial port directly, while both sides of the traffic stay on screen. A fast network feeding a slow port is throttled automatically, and whatever still has to be dropped is counted until you clear it.

  • Transparent forwarding, in one direction or both
  • RFC 2217 server: a remote machine sets baud rate, framing and control lines as if the port were local
  • Modbus gateway converts TCP frames to RTU, and serves masters on a shared RS-485 bus one at a time
  • Several clients handled exclusively, by broadcast, or in turn
  • An address allowlist keeps strangers off the port
  • Both directions recorded into one time-ordered capture file
The bridge editor linking a serial connection to a TCP/UDP endpoint in both directions

Real interface from Serial Port Utility.

Deliver

Flash it, save the session, hand it over.

Push firmware into a bootloader over the connection you already have, keep the session in a project file, and carry device and licence records into Cloud Sync when debugging continues after deployment.

  • XMODEM, XMODEM-CRC, XMODEM-1K, YMODEM and YMODEM-G, both directions
  • Works over serial, TCP and RFC 2217 remote serial ports
  • Sessions saved as .spu project files and reopened on launch
  • Cloud Sync connects device records, licence status and message history
File transfer (XMODEM / YMODEM) Web remote debugging with Cloud Console
The Cloud Console showing connected devices and their status

Real interface from Serial Port Utility.

Use Cases

Worked scenarios, from wiring to verification.

Each one names the topology, the settings that matter and the result you should be able to observe.

See all scenarios

Debug a serial port from anywhere on the Web

Use Cloud Console across locations and NAT without routing directly to the site or opening an inbound TCP port.

  1. On-site SPU
  2. Cloud Console
  3. Browser anywhere
Open scenario

Connect directly with RFC 2217

Reach a serial server directly over a LAN or VPN and control its serial parameters as well as its data.

  1. RFC 2217 Client
  2. Reachable LAN or VPN
  3. On-site serial server
Open scenario

Connect an isolated site outward

Use an outbound TCP client when the device site cannot accept inbound connections.

  1. Serial device
  2. SPU TCP Client
  3. Central server
Open scenario

Monitor a serial conversation inline

Capture both directions between an existing host and device without changing the protocol.

  1. Existing host
  2. SPU bridge
  3. Serial device
Open scenario

Forward serial telemetry over UDP

Turn NMEA or sensor messages into correctly framed UDP datagrams for a LAN collector.

  1. Sensor
  2. SPU framing
  3. UDP collector
Open scenario

Poll a Modbus RTU device reliably

Build a repeatable request, verify CRC and separate timeout from framing failures.

  1. SPU poll command
  2. RS-485 adapter
  3. Modbus device
Open scenario

Capture an intermittent fault overnight

Record timestamped traffic with bounded files and preserve a useful incident window.

  1. Serial link
  2. SPU logging
  3. Rotated evidence files
Open scenario

Update device firmware over serial

Send an image to a bootloader with YMODEM, locally or through a device server.

  1. Firmware image
  2. SPU YMODEM
  3. Device bootloader
Open scenario
Next Step

Try it against your own device.

Install the build for your system, then follow the scenario closest to the link you are debugging.

Get the Latest Build See all scenarios