The serial port
The port list is live and shows descriptions, so you can tell COM7 — USB-SERIAL CH340 from the modem that has been in the machine since 2011.
| Setting | What to know |
|---|---|
| Rate | Up to 3 000 000 baud; changeable without reopening the port |
| Parity and stop bits | Also changeable on the fly |
| Flow control | Hardware or software, or none — most industrial devices use none |
| DTR and RTS | Manual control; on RS-485 adapters RTS often drives the direction |
| BREAK | Sent as a button, for devices that use it to enter a bootloader |
TCP client and server
- Client. Connects to a device that listens.
TCP_NODELAYis set, because a request-response protocol suffers badly from packet coalescing. Reconnection after a drop has a configurable delay. - Server. Accepts several clients, lists them, and sends either to all of them or only to the one that connected last — which is what you want when a device dials in and you are answering it.
Quick commands
The panel on the right holds the frames you send repeatedly. Each is edited in a dialog that previews the exact bytes, so a command with a checksum can be checked before it goes out rather than after the device has done something unexpected.
Buttons are reordered by dragging, and the arrangement is part of the workspace, so it survives a restart.
The speed test
Measures the round trip — request out, answer back — and charts it with statistics. It is the tool for comparing a direct serial link with the same device reached through a converter and a network, when somebody claims the network is “too slow” and nobody has measured it.
When the line is silent
| Symptom | Where to look |
|---|---|
| The port will not open | Another program is holding it — a previous instance, or a vendor tool in the tray |
| Nothing arrives at all | Baud rate, or A and B reversed on RS-485; the modem-line display shows whether anything is connected |
| Garbled characters | The wrong baud rate or parity; the hex view shows whether the bytes are close to correct or completely wrong |
| Answers arrive but are truncated | The end-of-line rule is splitting frames that are not line-based — use the hex view |
| TCP connects and immediately drops | The device only accepts one connection and another client already has it |
| The SSH tab fails to connect | Wrong credentials, or the gateway does not permit forwarding to that address |