536

Port 536/udp carries the IANA-registered service name opalis-rdv, associated with the Opalis Windows job-automation product line; it has no documented legitimate reason to be reachable from the public internet and should stay confined to whatever internal network still runs that software, if any does.

IANA lists opalis-rdv identically on both 536/tcp and 536/udp, assignee Laurent_Domenech, with a blank Reference field — no RFC or other spec backs the registration. The registry's description string is simply the service name itself, so little beyond the name and its product-line association is independently documented.

Opalis Software made a Windows workflow/job-automation product; Microsoft acquired the company in 2009 and folded it into Opalis Integration Server, later renamed System Center Orchestrator. Microsoft's own connectivity-requirements documentation for that successor product lists TCP 1433, TCP 135 plus dynamic RPC, TCP 5314, and TCP 139/445 as the ports it uses — port 536 does not appear anywhere in that document.

A prior version of this entry described opalis-rdv as a Dynamic Data Exchange (DDE) rendezvous channel bound to a specific "Opalis Robot Server" component. That framing has been dropped: the cited sources do not carry it. GRC's port-536 page contains only the bare service name and purpose string, with no mention of DDE, rendezvous, or a Robot Server component, and no independent source was found that does.

Exposure

opalis-rdv is a legacy Windows automation service-name registration with no evidence of current mainstream deployment; treat any host answering on 536/udp as an internal legacy artifact, never as something meant to face the public internet.

Notable CVE

none recorded in the NVD as of an August 2026 search.

Malware association

none found; GRC's port-536 listing shows only the bare service name with no trojan/malware note.

Prevalence

essentially unseen in the wild — nmap-services open-frequency for 536/udp is 0.000428 (~0.04%), and for 536/tcp 0.000025 (~0.003%).

IANA assignment

opalis-rdv — description "opalis-rdv"; reference (blank — no RFC cited); assignee Laurent_Domenech; dual-registered 536/tcp + 536/udp [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry opalis-rdv 536/udp

Range class

well-known (0–1023) [Confirmed]

Prevalence

nmap-services open-frequency 536/udp ≈ 0.000428 (~0.04%); 536/tcp ≈ 0.000025 (~0.003%) [Confirmed] — this site's own tooling

Related ports

536/tcp (identical dual registration); Opalis Integration Server ports TCP 1433, 135(+dynamic RPC), 5314, 139/445 [Confirmed] — https://learn.microsoft.com/it-it/archive/blogs/opalis/overview-of-opalis-integration-server-connectivity-requirements

Primary use

IANA-registered service name opalis-rdv, associated with the Opalis product line (Opalis Software's Windows job-automation tools, later Opalis Integration Server / System Center Orchestrator after Microsoft's 2009 acquisition); the registry carries no description beyond the bare name and no live source ties the assignment to a Dynamic Data Exchange mechanism or a specific "Robot Server" component

Other/unofficial uses

none found beyond the general Opalis product-line naming association; Microsoft's connectivity docs for the successor product (Opalis Integration Server / System Center Orchestrator) do not list port 536

Security implications

no CVE or malware association found as of an August 2026 search; legacy/obscure service-name registration with negligible real-world exposure today

Typically seen on

legacy Windows hosts running Opalis-era automation software (pre-Microsoft-acquisition era); otherwise essentially never seen [Likely]

Analyst note

An open port 536/udp is unusual today; investigate as a legacy automation artifact rather than assume malicious intent, but do not expect a modern Opalis/System Center Orchestrator deployment to use it.