What This Port Is
Port 3608 is officially assigned to trendchip-dcp — the TrendChip control protocol — registered with IANA in September 2002 by Ming-Jen Chen of TrendChip Technologies Corp.1
TrendChip no longer exists.
The Range It Belongs To
Port 3608 sits in the registered port range (1024-49151). These ports are maintained by IANA and assigned to specific services on a first-come, first-served basis. Unlike the well-known ports (0-1023), registered ports don't require IANA approval — just a registration request. They're also not reserved in any hard sense: if TrendChip's protocol never ran on your network, port 3608 was just an empty number.2
Who TrendChip Was
TrendChip Technologies Corp. was a Hsinchu, Taiwan-based semiconductor company founded in 2001. They built the chips that powered ADSL and ADSL2+ routers — the little boxes that connected millions of homes to the Internet in the early 2000s. Their TC3162 chipset was among the first ADSL2+ solutions in Asia.3
They registered port 3608 for DCP (device control protocol) — a protocol for managing and controlling router hardware running their chips. If you had a budget DSL router from that era, there's a reasonable chance it had TrendChip silicon inside.
In 2012, Ralink Technology acquired TrendChip. Ralink was then acquired by MediaTek. MediaTek folded TrendChip's broadband technology into EcoNet (HK) Limited, which was later acquired by Airoha, another MediaTek subsidiary.4
TrendChip's chipsets — including those that ran DCP on port 3608 — had shipped over 200 million units worldwide before the brand ceased to exist. The protocol quietly died with the company. The IANA registration did not.
What Runs on It Now
Nothing registered. If you see traffic on port 3608 today, it's not the TrendChip control protocol. It's something that chose an available-looking number. Malware, custom applications, and misconfigured services all sometimes land on ports like this one — obscure enough to feel uncrowded, registered enough to look legitimate.
How to Check What's Listening
On Linux or macOS:
Or with the older tool:
On Windows:
If something is listening on port 3608 and you didn't put it there, investigate. The legitimate TrendChip DCP protocol almost certainly isn't running on your system.
Why Unowned Ports Matter
The registered port range has over 48,000 ports. Many are assigned to protocols that, like trendchip-dcp, belong to companies or products that no longer exist. These orphaned registrations are harmless but useful to understand: they mean the port looks assigned when you check a database, without there being any active service to conflict with. They're the Internet's equivalent of a name on an office door for someone who left years ago.
IANA doesn't actively reclaim ports from defunct organizations. The registry grows; it rarely shrinks.
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