PortDock

PortDock Port Inspector Guide

Read-only inspector for COM ports, network adapters, PC settings and wireless

About

PortDock Port Inspector gathers, for one COM port, what you would otherwise dig out of Device Manager, Event Viewer and the registry: the device and driver (provider, version, date, INF), the Device Manager problem code and what it means, the USB chip (VID/PID), device settings such as the FTDI latency timer, the Windows port default, USB power saving, recent plug and driver history, and COM number reservations.

It only reads, without administrator rights. It never changes the registry, device settings or drivers, and it does not scan other programs' handles.

With TX tied to RX, «Connection test» checks that bytes come back unchanged at each speed and measures the round trip (ms); it also tells whether a 2-wire RS-485 adapter receives what it sends (echo).

Results are marked «No issue found (in what was read) / Worth a look / Problem / Could not read». It speaks only about what the PC can read, so what the PC cannot see — wiring, termination, bias, ground — is always listed at the bottom.

Getting started

  • 1. Click a port in the «COM ports» list on the left. To include devices plugged in earlier, turn on «Show devices not connected now».
  • 2. Cards appear in the middle: device and driver, USB path (for USB devices), settings, power saving, history, COM number reservations, connection test, network adapters, this PC. Each card header shows a result; for «Worth a look» or «Problem» the reason is on the line below.
  • 3. For a problem report or question, use «Copy text» (or «Save…») at the top. User folder paths are masked as «~».
  • On first start these steps show as a card in the empty area. «Don't show again» turns it into a one-line hint.

Screen layout

  • Left: the COM port list (connected first, by COM number). Devices with a problem code show a red number, devices not connected now show «not connected», and COMs not in the port device list (modems, virtual COM drivers …) show «no device info». ↻ reloads the list.
  • Tabs at the very top of the middle: «COM ports» (the cards below) and «Wireless (Wi-Fi, Bluetooth)» — the wireless tab looks at this PC's Wi-Fi and Bluetooth regardless of the chosen COM port (see «Wireless»).
  • Top toolbar: the chosen port and the overall result (the heaviest of the cards), read time, «Refresh» (F4), «Copy text», «Copy JSON», «Save…».
  • Click a card header to fold or unfold it (remembered per card). With «Expand all» in Settings every card starts open.
  • The «What the PC cannot see» box with portdock.dev guide links is always shown at the bottom.
  • 📌 in the header: always on top — keeps this window above others (same as «Always on top» in Settings).
  • The window title shows the current state (e.g. «COM3 115200 8N1 · Connected ● REC — PortDock Serial»), so you can tell windows apart on the taskbar.
  • At 900 px wide or less (e.g. half-screen snap) the left panel folds away and a summary line with «⚙ Connection» (Port Inspector: «⚙ Ports», Net Scan: «⚙ Scan settings», Hardware Tester: «⚙ Checks») and the connect button appears. The language, 📌, !, AI, ? and ⚙ buttons move to the right end of that line. «⚙ …» opens the panel; ✕ or clicking outside closes it.
  • AI in the header: Copy for asking AI — builds text for an AI chat with a question template («list likely causes and the order to check them»): program, version, connection settings, errors in this session and recent traffic (HEX, text and note lines; check results in Port Inspector and Hardware Tester, found devices in Net Scan). The template fits the app: device and wiring for the communication apps, PC and wireless setup for Hardware Tester, finding network devices for Net Scan, ports and drivers for Port Inspector. Review the preview and «Copy» — it only goes to the clipboard. Above 8,000 characters the oldest traffic lines are removed and the count is noted. User folders, default Windows PC names (DESKTOP-… etc.), the last 3 bytes of MAC addresses and public IPs are hidden; private IPs are kept by default because causes such as different subnets need them («Hide private IPs too» hides them).
  • Whatever you paste goes to that AI service. Check device and company details before pasting.
  • Text size: Ctrl+mouse wheel or Ctrl+= / Ctrl+- makes it larger or smaller, and Ctrl+0 returns to the default (13 px). It is the same value as «Font size» in Settings, so it is kept next time.

Result marks

  • No issue found (in what was read): nothing in the values read looks wrong. It does not mean the wiring or device settings are fine.
  • Worth a look: a value that may or may not matter (e.g. FTDI latency timer 16 ms, power saving on, COM17 or higher). Usually fine as is; check it if it matches your symptom.
  • Problem: used only for facts — a Device Manager problem code, two devices holding the same COM number, bytes lost or changed in the loopback test.
  • Could not read: the value could not be read because of rights, policy or the driver. The other cards are still read; the card or the line below says what and why.

Device, driver and problem codes

  • Shows name, COM number, instance ID (⧉ copies it), VID:PID, chip, USB product name (as reported by the device), manufacturer, location (USB hub port), driver provider, version, date, INF, service name, status, last plugged in / removed and first install time.
  • Problem codes are the numbers Device Manager shows (10 cannot start, 28 no driver, 43 device reported problems …). Meanings are condensed from Microsoft's «Device Manager error messages»; «What to try» lists what to try first with a USB-serial adapter.
  • The chip comes from a VID/PID table (FTDI, Prolific PL2303, WCH CH34x, Silicon Labs CP210x … — only numbers listed by the vendors or public driver device tables). Clones reuse the same numbers, so it is «the name for the number the device reports».
  • Clues: FTDI PID 0000 (a 2014 driver rewrote clone chips' PID to 0) and Prolific + problem code 10 (common with discontinued revisions or clones) are flagged «Worth a look» — not conclusive.
  • «Devices above»: when a COM device sits under a separate USB device (as with FTDI), its name.

Settings — port default and FTDI latency timer

  • «Windows port default» is the value in the registry Ports key (e.g. 9600,n,8,1). The speed and parity a program sets when it opens the port take precedence, so it rarely matters for a device link.
  • «Device settings (Device Parameters)» shows the values the driver stored for the device, names and values as is. Explanations are added only for names confirmed by public documents (FTDI LatencyTimer, PortName).
  • FTDI latency timer (LatencyTimer, default 16 ms): unless the buffer fills, data waits this long before going to the PC. Fast short request/response traffic such as Modbus RTU polling can look slow, so 16 or more is «Worth a look».

USB path

  • For a USB adapter, each step from the device up through hubs and the root hub to the USB controller is shown on its own line — the same chain as Device Manager's «Devices by connection» view.
  • Port: which port of the hub just above it is plugged into. Negotiated speed: what that hub reports (Low 1.5 Mbps · Full 12 Mbps · High 480 Mbps · SuperSpeed 5 Gbps or more). Most USB-serial chips connect at Full Speed, which is far faster than the serial line, so it is not slow.
  • Hub power: bus-powered (power only over USB, no adapter) or self-powered. With several devices on a bus-powered hub, power can run short.
  • If a device that reports USB 3 capability is connected at a lower speed, it is marked «Worth a look» — the cable or a USB 2 port may be why. Going through hubs and bus-powered hubs are noted only, not judged.
  • Hubs are only sent status queries (no administrator rights needed). Hub reset counts and current draw are not read.

Power saving

  • «USB selective suspend» is the power options value (Advanced settings → USB settings), read for plugged in and on battery.
  • «Allow the computer to turn off this device to save power» is the Power Management tab in Device Manager. Only this device and the USB devices or hubs above it that have the setting are listed (the driver must support it).
  • When on it is «Worth a look». Usually harmless, but on a PC that monitors or logs for long periods, consider turning it off if the adapter drops now and then.

History

  • The last plugged-in and removed times from the device properties, plus events for this device and the USB device above it from the event logs (Microsoft-Windows-Kernel-PnP/Configuration, and Kernel-PnP / UserPnp in System) over the chosen period (7, 30 or 90 days), newest first, up to 200.
  • 410 is device started (every plug-in), 400 configured (driver install), 420 deleted, 411 start problem. The descriptions are written by Windows (in the PC's language).
  • Days with 3 or more reconnects, or start-problem / error events, are «Worth a look» — check the cable, hub and power saving.
  • On a PC where the event logs cannot be read (company policy), «Could not read» appears with the reason.

COM number reservations

  • Windows keeps a COM number reserved even after the device is removed (ComDB under COM Name Arbiter in the registry), which is why a new adapter may get a high number such as COM15.
  • «Reserved numbers» = ComDB, «Devices connected now» = numbers of plugged-in devices, «Numbers held by devices not connected now» = earlier devices, «Reserved numbers with no device» = reserved but no known device, «Numbers held by more than one device» = two devices got the same number (only one can be used at a time — «Problem»).
  • COM17 or higher is «Worth a look» — some older programs only offer COM1–16.
  • «COM names openable now (SERIALCOMM)» lists the COM names drivers have open right now.

Connection test — loopback and echo

  • Disconnect the device from the line or bus first. Test bytes could reach a device as commands, so «Start test» asks once more.
  • Loopback: on a DB9 tie pin 2 (RX) to pin 3 (TX); on a TTL adapter tie TX to RX. For each chosen speed (default 9600, 19200, 38400, 57600, 115200) it sends 256 random bytes in 32-byte chunks and compares what comes back (sent, same, lost, changed), then times 20 one-byte round trips (median and max, ms). If nothing comes back in the first chunk, that speed ends early.
  • The round trip includes USB latency, driver and program time. A median of 10 ms or more is «Worth a look» — possibly a USB adapter setting such as the FTDI latency timer (default 16 ms).
  • Error flags (framing, parity, overrun, break) are asked from the driver at the end (ClearCommError). Whether a USB adapter driver raises them varies by chip, so «none» does not guarantee there were no errors.
  • 2-wire RS-485 echo: with no device on the bus it sends «PortDock echo» at the chosen speed; if the same bytes come back it reports an echo. With such an adapter your own bytes show up before the reply (PortDock Serial's echo handling and the Modbus tools' echo skip deal with this).
  • If another program has the port open you get «busy». To find which one, search for the «Service» name from the device card (e.g. FTSER2K, usbser) with «Find → Find Handle or DLL» in Microsoft Process Explorer.
  • A 4-wire (RS-422) adapter can be loopback-tested by tying TX+ to RX+ and TX− to RX− (check the terminal names in the adapter manual).

Network adapters on this PC

  • «Read adapters» lists each physical adapter with connection, link speed, duplex (full/half), IPv4 and gateway.
  • Link speed and duplex are what the adapter negotiated with the switch. With 10 Mbps or half duplex, check the cable and auto-negotiation on the switch port. To find device IPs, use PortDock Net Scan.
  • For each adapter it also reads the Device Manager «Advanced» tab values (jumbo frames, receive/transmit buffers, interrupt moderation, EEE, flow control, speed/duplex, RSS — shown value and registry value), «allow the computer to turn off this device», receive errors and discards (cumulative), the network profile (Public, Private, Domain) and whether the firewall is on for it. All without administrator rights.
  • Pick a «Use» to look at it for that use. «General» looks at link, duplex and errors only; «GigE camera» adds jumbo frames, receive buffers, power saving, Public profile, firewall and EEE; «PLC / Modbus TCP device» adds power saving, Public profile and EEE. Either way it marks at most «Worth a look», never «Problem».
  • With «GigE camera», values from camera vendors' public docs (Basler, MathWorks, Balluff, Teledyne) are shown side by side with links. They are not PortDock recommendations; where vendors differ (interrupt moderation rate, for example) both are shown.
  • Jumbo frames must match on the PC, the camera and the switch — the PC value alone cannot show there is no issue. If a driver does not use the standard keyword, that item shows «not reported by this driver».
  • For the firewall, only whether each profile is on is read. Per-port and per-program rules are not read here.
  • To change values, use Device Manager → Network adapters → the adapter → Properties → «Advanced» and «Power Management» tabs (administrator).

This PC — equipment PC settings

  • «Read this PC's settings» reads, without administrator rights, the Windows settings and recent records that often matter on a PC running equipment. These are PC-wide values, not tied to the chosen COM port.
  • Power and sleep: fast startup (not in effect when hibernation is off), the current power plan's sleep, hibernate and display-off times, PCI Express Link State Power Management and USB selective suspend — plugged in and on battery.
  • Updates and restarts: update policy (group policy values — automatic updates, AUOptions, no auto-restart with logged-on users, drivers excluded), active hours, and pending restarts (Windows Update RebootRequired, component servicing RebootPending, files scheduled to be replaced at next start).
  • Screen saver and time: the screen saver with its wait time and logon screen, the time sync type (NTP, domain, no sync), server and W32Time service start type, and from time service events the last «synchronizing with time source» record and the warning count.
  • Recent records: counts and last times of unexpected shutdowns (Kernel-Power 41, EventLog 6008) and hardware warnings and errors (WHEA-Logger, disk, Ntfs) in the chosen period (7, 30 or 90 days). The PC cannot tell what caused an unexpected shutdown (power cut, power button, hang).
  • With «Use» set to «General PC», settings are only listed and just the records (unexpected shutdowns, hardware errors) are marked «Worth a look». With «Equipment PC», fast startup on, sleep, USB selective suspend, no policy holding back automatic restarts, a pending restart and an unsynced clock are marked too.
  • The right values differ from site to site. Most of them (updates, sleep) are right to keep on an office PC, so it marks at most «Worth a look», never «Problem». It never advises turning updates off — for active hours and restart policies see Microsoft's «Configure policy settings on IoT devices».
  • Each item shows «Where to change» (Settings, Control Panel or group policy path). This program does not change them.
  • What only an administrator can read — programs keeping the PC awake (powercfg /requests), Microsoft Defender exclusions, disk SMART — is not read and is listed as «Administrator only».

Wireless — Wi-Fi and Bluetooth

  • The first time you open the «Wireless (Wi-Fi, Bluetooth)» tab at the top of the middle area, it reads this PC's Wi-Fi and Bluetooth without administrator or location permission. It is not tied to the chosen COM port. It sends no traffic such as pings and does not scan for nearby devices. F4 reads again.
  • Wi-Fi: the wireless adapter (product name, connected or not), its driver (provider, version, date), the device's «Allow the computer to turn off this device to save power», the power plan's «Wireless Adapter Settings → Power Saving Mode» (plugged in and on battery), disconnect records in the chosen period (7, 30 or 90 days — WLAN-AutoConfig event 8003 in Event Viewer, counted by reason with the last time), and driver warnings and errors (System log).
  • Windows ties the connected network name (SSID), signal and channel to location permission, so they are not read. From the disconnect records only the reason code and text are taken; network names are dropped. The reason text is what Windows logged (in the PC's language), so it may be a symptom rather than the cause.
  • Bluetooth: the adapter (radio), driver and device power saving, the USB path for a USB dongle (whether it goes through a hub), the state of the Bluetooth Support Service and the Audio Gateway service, BTHUSB and BTHPORT warnings and errors in the System log, and whether Bluetooth audio endpoints are hands-free (calls) or stereo and which one is the default.
  • Marked «Worth a look»: device power saving on, wireless power saving even when plugged in, disconnects averaging 5 or more a week, error-level driver or Bluetooth events, a Bluetooth dongle behind a USB hub, the Bluetooth Support Service stopped or disabled, a hands-free endpoint as the default output, and a Device Manager problem code. These are only possible causes, so it never says «Problem».
  • Hands-free: when a meeting or call app opens the headset microphone, a Bluetooth headset switches to the hands-free profile and the sound becomes mono and lower quality. For music and video, make the «Headphones» (stereo) endpoint the default output; setting the call app's microphone to the PC's own microphone avoids the switch.
  • Each item shows «Where to change», and the Bluetooth items link to Microsoft's support article «Bluetooth keeps disconnecting in Windows». This program does not change any setting.
  • «Copy text», «Copy JSON» and «Save…» on this tab contain only the wireless results and hide Bluetooth audio device names as «Device 1» and so on. The screen still shows the names.
  • What the PC cannot see: the network name, signal, channel and nearby Wi-Fi, the router and provider side and internet speed, 2.4 GHz interference (microwave ovens, USB 3 devices), the headset's battery and firmware, and the list of paired devices. The Windows wireless report (netsh wlan show wlanreport) needs administrator rights and is not read.
  • To log when and how often drops happen over time, use the «Wi-Fi / internet drop log» tab in PortDock Hardware Tester (also noted at the bottom of this tab).

What the PC cannot see

  • RS-485 A/B (+/−) swapped — makers label them differently.
  • Termination (120 Ω at both ends) and bias resistors, ground / common (GND) and shielding.
  • Device-side settings (Slave ID, baud, parity), cable length and noise.
  • Check these separately with the guides at the bottom (RS-485 wiring, bias and termination, USB serial latency, Modbus no response, RS-232 DB9 and null modem).

Fixing things (by hand)

  • This program never changes values. Change them yourself in Windows (administrator rights may be needed).
  • FTDI latency timer: Device Manager → Ports (COM & LPT) → device properties → Port Settings → Advanced → «Latency Timer (msec)». FTDI does not recommend 1, so try about 2–4. The adapter may need replugging to apply it.
  • Device power saving: Device Manager → device (or the USB device / hub above it) properties → Power Management → turn off «Allow the computer to turn off this device to save power».
  • USB selective suspend: Control Panel → Power Options → Change plan settings → Change advanced power settings → USB settings → USB selective suspend setting «Disabled».
  • This PC's settings (fast startup, sleep, updates, time sync …): use «Where to change» shown for each item in the This PC card.
  • Devices not connected now and orphan COM numbers: Device Manager → View → «Show hidden devices», then uninstall the dimmed port devices to free their numbers. Editing ComDB in the registry by hand is not recommended — a mistake can give two devices the same number.

Export

  • «Copy text»: copies each card's result, the values read, the connection test and «What the PC cannot see» as text (handy for issues and mail).
  • «Copy JSON»: copies every value read as JSON.
  • «Save…» (Ctrl+S): a .txt name saves text, a .json name saves JSON.
  • User folder paths (C:\Users\name\…) are masked as «~». Device instance IDs and serial numbers stay in, so have a look before pasting.
  • «Open in Serial»: opens PortDock Serial with the selected port (a device plugged in now) filled in. Press connect in that window. If Serial is not found on this PC, the port name is copied and the download page is offered.

Settings

  • ⚙ sets language, theme, font size, «Always on top» and problem reporting.
  • «Always on top»: keeps this window above other windows (same as 📌 in the header).
  • «Expand all (expert view)»: shows the groups that are normally collapsed (advanced connection, receive settings, fault injection, statistics, scan options, triggers, auto-reply …) open. Folding one while it is on lasts only for this run. Turning it off returns each group to its remembered state.
  • «Send usage statistics» (off by default): when on, the program sends an anonymous summary to Aptabase (EU) once, as you close the window — how many times each feature was used (connect, send, read … — counts only), minutes open, program/Windows version, display language and installed/portable edition. Traffic, IP addresses, ports, COM names, file paths and PC/user/device names are never sent. You're asked once on first run (closing the prompt without choosing means no), and you can turn it off here at any time. If you're offline or sending fails, the data is dropped. Builds without this option never send statistics.
  • Once you answer the usage-statistics question in one PortDock app (the prompt or this option), other PortDock apps on this PC that have not asked yet use that answer as their starting value instead of asking again (portable copies: those in the same folder). Each app can still change it here, and an imported settings file never turns it on. Only «asked» and your choice are stored (installed: %LOCALAPPDATA%\dev.portdock\shared-consent.json, portable: portdock-data\shared-consent.json).
  • «Check for new versions (once a day)» (off by default): when on, the program asks GitHub (api.github.com) once a day for PortDock's latest release only. If a newer version exists, a notice bar with a «Release page» button appears at the bottom of the window. No data is sent and nothing is downloaded or installed. «Don't remind me about this version» silences that version. The «Check for updates» button under «About» still just opens the release page.

Shortcuts and tips

  • F4: refresh (list, chosen port and history).
  • Ctrl+S: save the result.
  • F1 or the ? button: this help. Close it with Esc.
  • Hover over a field to see a tooltip.

Troubleshooting

  • Empty list: this PC has no COM port device. Plug an adapter in and press ↻; to see earlier devices, turn on «Show devices not connected now».
  • An adapter is plugged in but not listed: without a driver it may show under «Other devices» instead of «Ports» (problem code 28). Check Device Manager and install the chip vendor's driver.
  • «Could not read» (WMI, event log): appears on PCs where company policy blocks it. The other cards are still read.
  • Nothing comes back in the connection test: check the TX–RX link, adapter power and LEDs, and that the adapter accepts that speed.
  • The program does not open: Microsoft Edge WebView2 is required (included in Windows 11).

Terms

  • Problem code: The number Device Manager gives a device. For example 10 = the device cannot start, 28 = no driver installed.
  • Loopback: TX wired to RX (e.g. pins 2 and 3) so whatever is sent comes back. Used to test the port and cable alone.
  • Baud (bps) · 8N1: Bits per second; both sides must match. 8N1 = 8 data bits, no parity, 1 stop bit.
  • DTR · RTS: Serial control lines. Some devices only send while DTR is on, and some RS-485 adapters switch send/receive direction with RTS.