Internet-Security.com TCP port 3129 details

Malware use: MyDoom/Novarg variants opened a backdoor on 3127–3129/TCP (including 3129), enabling remote control; after the outbreak, widespread Internet scans probed 3129 to find infected hosts.
This association is exploitative: attackers leveraged the 3129 backdoor to issue commands or install additional payloads on compromised systems.
Aside from this malware-related use, there is no widely documented, standard legitimate software that defaults to TCP 3129.

TCP 3129