I need help redirecting a COM port on my Windows PC because an older device I use relies on a specific COM port number. After a recent update, the assigned port changed and now my device won’t connect. Can anyone walk me through the steps to redirect or reassign the COM port number so I can get my device working again?
Ugh, classic Windows update roulette strikes again. Been there—one of my old barcode scanners only worked on COM3 for whatever ancient reason the universe decided. Here’s the usual way to remap it:
- Hit Windows key + X, pick Device Manager.
- Expand “Ports (COM & LPT)”.
- Right-click your device > Properties > Port Settings tab > Advanced.
- You’ll see “COM Port Number” at the bottom—pick the COM port your device is obsessed with (probably shows as “(in use)” but ignore that if you know nothing else is using it).
- Click OK a bunch of times, unplug/replug the device if needed.
Half the time, Windows acts like you’ve asked for free pizza and pretends it can’t change the port because “it’s in use.” If so, unplug everything you can, reboot, and try again.
If you’re on a network or need to “move” the port to another PC (like virtual machines or remote setups), check out Serial to Ethernet Connector—it lets you create virtual copies of a COM port over your network, so the old device still thinks it’s talking to the right port number. Used it in a pinch with legacy CNC gear. Insanely helpful.
Also, if you find yourself working with legacy systems or need to fine-tune serial port management, this guide on streamlining legacy device connectivity with serial port mapping explains some tricks for enhancing compatibility.
Pro tip: Make note of that COM number, Windows loves to “forget” it after updates. Welcome to the joys of legacy tech!
Not to start an OS flame war, but why does Windows ALWAYS reshuffle COM ports like it’s playing musical chairs after every update? Anyway, @sternenwanderer nailed most of the standard tactics for mapping COM ports—but to add to the chaos, sometimes Windows gets “sticky” with old devices and COM assignments, especially after a cumulative update or plugging into a new USB slot.
Here’s another angle: Pop open regedit (yeah, I know, it’s dicey) and poke around at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter. Sometimes, deleting “phantom” devices or freeing up COM numbers stuck in the registry does the trick when Device Manager refuses to listen.
Also, if you’re dealing with software that’s impossibly stubborn (looking at you, 90s lab equipment), you might want to try a more robust solution than Windows’ half-baked serial management. Using a dedicated COM port redirector application is worth its weight in gold for this—something like Serial to Ethernet Connector. It lets you virtually assign and map those pesky COM ports locally or even route them over your network. Super handy when old gear needs “COM1 only or bust” and Windows is like “surprise, it’s now COM14 lol.”
And for snag-free downloads and more info about these pro-level tools, check out how you can unlock the potential of your legacy devices.
Last thing, don’t sleep on making a note (or screenshot) of successful port numbers/configs somewhere, because, let’s be real—Windows doesn’t love keeping your settings stable. Reboots break hearts (and ports). Anyone else fed up with this, or have even weirder port number voodoo to share?
Let’s get real: Windows COM port mapping is basically Jenga—you never know which block gets pulled next. The registry trick is gutsy, but unless you’re cool bricking your boot (been there), I’d stick with the Device Manager angle first. Sometimes though, Device Manager and the registry both gaslight you, especially if you’ve had a zillion devices plugged into your system over the years.
Here’s a curveball: try using Windows’ “Show hidden devices” (View menu in Device Manager), then nuke those ghostly leftover COM ports. They can block you from grabbing the number your legacy gadget wants, and sometimes removing these undead entries frees things up massively.
Not a fan of kludging things together every update? Enter Serial to Ethernet Connector. Besides what’s already been mentioned, one pro is it lets you centralize your legacy gear—so if your antiquated medical scale or label printer lives in a dank network closet, you can “pipe” its COM port anywhere on your LAN. No more musical USB chairs. Downside: it’s not free, and setup can be overkill if you’re strictly plugging in one device on one PC. Still, as compared to the solutions from competitors like those further upthread, it handles modern Windows quirks with less voodoo.
Bottom line: If Windows keeps reassigning ports or your software throws tantrums unless it sees COM1, consider both a thorough device sweep and something bulletproof like Serial to Ethernet Connector. But yeah, keep a sticky or screenshot of your settings, or next reboot you’ll be right back here.