190

Port 190/tcp is registered with IANA as gacp, short for "Gateway Access Control Protocol," and is dual-registered on both TCP and UDP with an identical description on both rows. The assignee/contact on file is C. Philip Wood, and the registry's Reference field is blank — no RFC is cited for this assignment, and none was found independently, so the reference stays blank rather than invented. The assignment itself is old: port 190 already appears in RFC 1340 ("Assigned Numbers," July 1992), one of the early IANA numbers registries, showing the entry has existed since at least the early 1990s even though the current live IANA registry lists no formal specification document. Several third-party port-lookup databases (t1shopper, tcp-udp-ports.com, SpeedGuide) independently describe GACP's purpose the same way: a client/server protocol for establishing and managing a user's login session on a remote-access gateway or router, i.e., a mechanism for gateway/router devices to control and track remote access sessions. None of these secondary sources cite a protocol spec or RFC either, so that functional detail is treated as a corroborated-but-secondary characterization rather than a primary-source fact. No actively maintained modern software, appliance, or vendor product was found documenting current use of GACP on port 190, and no evidence surfaced of the port being associated with malware, trojans, or notable scanning activity; it appears to be a largely dormant, historical assignment today.

IANA assignment

gacp — "Gateway Access Control Protocol"; assignee/contact C. Philip Wood; dual-registered 190/tcp + 190/udp (identical rows) [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml

IANA reference/RFC

blank in the live registry — no RFC or spec document is cited there, and none was independently found, so this is left blank rather than fabricated [Confirmed] — https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml

Range class

well-known (0–1023) [Confirmed]

Historical depth

port 190 already appears as an assigned number in RFC 1340 (July 1992), indicating the assignment predates the modern registry by decades [Likely] — https://datatracker.ietf.org/doc/html/rfc1340

Primary/protocol purpose

client-server protocol to establish and manage a user login session on a remote-access gateway/router; description repeated consistently across three independent third-party port databases, but none cite a spec document, so treated as secondary-source characterization [Likely] — http://www.t1shopper.com/tools/port-number/190/, https://tcp-udp-ports.com/port-190.htm, https://www.speedguide.net/port.php?port=190

Current software/usage

no actively maintained software or vendor product documented as implementing GACP on port 190 today was found in this pass [Unknown]

Security/malware associations

no evidence found of port 190 being linked to malware, trojans, or backdoors, and it does not appear on common trojan-port reference lists checked; a responsive 190/tcp in a live scan is more plausibly a misconfigured/legacy or unrelated service than active GACP traffic, but this is a reasoned inference, not a dated report

[Unknown] — http://www.chebucto.ns.ca/~rakerman/trojan-port-table.html

Port 190/udp is registered with IANA under the service name gacp, described as "Gateway Access Control Protocol," with assignee C. Philip Wood. The registry's Registration Date, Modification Date, Reference (RFC), Service Code, Unauthorized Use Reported, and Assignment Notes fields are all blank for this row — there is no RFC that defines GACP, unlike many well-known-range services that point to a specific standards document. Port 190 is dual-registered: the TCP row (190/tcp) carries the identical service name, description, and assignee as the UDP row, meaning IANA reserved the number across both transports for the same nominal service rather than assigning them independently. Beyond the bare registry entry, verifiable information is thin. A handful of secondary port-reference sites describe GACP informally as a protocol for establishing an administrative login session on a remote-access gateway or router, but no primary specification could be located to confirm the mechanism, so that description is treated as unverified. No vendor, daemon, or product could be identified as implementing GACP on port 190 in current or historical use, and no CVEs, malware families, or scanning campaigns specifically target this port. Any UDP traffic observed on port 190 in the wild is more plausibly incidental background scan noise than evidence of a live, targeted service — the nmap-services dataset records an open-frequency of about 0.000428 for 190/udp (roughly 4 in 10,000 scanned hosts), and no other telemetry source confirms or contradicts that reading. In short, 190/udp is a formally reserved but functionally obscure and effectively unimplemented IANA assignment.

IANA assignment

gacp — "Gateway Access Control Protocol"; assignee C. Philip Wood [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry line 467

IANA reference (RFC)

blank in registry — no RFC defines GACP [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry line 467; cross-checked https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xml

Registration/modification dates, service code, unauthorized-use flag, assignment notes

all blank in the source registry, left null (not invented) [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry line 467

Range class

well-known (0–1023) [Confirmed]

Prevalence

nmap-services observed open-frequency 190/udp ≈ 0.000428 (very low — roughly 4 in 10,000 scanned hosts in the nmap-services sample); the dual-registered 190/tcp side is rarer still at ≈ 0.000013 [Confirmed] — nmap-services dataset

Related ports

190/tcp (dual-registered gacp counterpart) [Confirmed]

Protocol purpose/mechanism

secondary sources describe GACP as a client/server protocol for an administrative login session on a remote-access gateway/router; no primary spec exists to confirm this

Common software implementations

none identified [Unknown]

Exposure/scanning notes

no CVEs, malware, or targeted scanning campaigns found; observed UDP traffic most plausibly routine background scan noise, unconfirmed

Dual-registration

190/tcp carries identical service name, description, and assignee as 190/udp [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry lines 466–467