29

Port 29/tcp is registered with IANA as msg-icp with the description "MSG ICP," with both the assignee and contact listed as Robert Thomas (shown as [Robert_Thomas] in the registry), and a blank reference field (dual-registered on TCP and UDP with identical metadata). This is one of the oldest entries in the assigned-numbers lineage: RFC 790 ("Assigned Numbers," September 1981) lists decimal 29 on the literal line 29 35 MSG-3 ICP [29,RHT], where "RHT" is Robert H. Thomas. The "MSG" here refers to the MSG interprocess-communication facility built for the ARPA-era National Software Works (NSW) project, and "ICP" to its Initial Connection Procedure — the sub-protocol that handled connection setup between cooperating processes; this expansion comes from secondary documentation rather than a single canonical RFC for port 29 itself, so it is tagged accordingly. Note that "MSG ICP" should not be conflated with the similarly named Message Send Protocol (MSP), which is a distinct, later service assigned to port 18. The IANA reference field for port 29 is blank — no RFC is cited by IANA for this row — and all of the registry's date, service-code, unauthorized-use, and assignment-note columns are likewise empty, so no registration or modification date can be honestly attributed to this entry; the earliest verifiable dated reference is RFC 790 (September 1981). For an analyst, port 29 is effectively a legacy reservation: there is no known modern software that binds to it by default, and no specific named malware, CVE, or documented scanning campaign targeting it was found. A handful of port-information sites carry a generic "flagged as a virus" disclaimer, but this appears to be boilerplate rather than a verified attribution — it is absent from the Trend Micro and Chebucto trojan-port reference tables. A responsive port 29 today is best treated as an unhardened or misconfigured host, or simply noise from internet-wide scanners probing low-numbered well-known ports; deny-by-default is appropriate.

IANA assignment

msg-icp — "MSG ICP"; reference (blank — no RFC cited in IANA registry); assignee/contact Robert Thomas ([Robert_Thomas]); dual-registered 29/tcp + 29/udp [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry (CSV lines 65–66)

Range class

well-known (0–1023) [Confirmed]

Prevalence

nmap-services observed open-frequency 29/tcp ≈ 0.000025 (very low — roughly 2 to 3 in 100,000 scanned hosts in the nmap-services sample); the dual-registered 29/udp side is higher at ≈ 0.00056 [Confirmed] — nmap-services dataset. The figure records scan-observed openness on the port number, not confirmed MSG ICP traffic, and quantifies the de-facto-rare reading [Confirmed]

Registration / modification date

blank in the IANA registry — none cited; do not attribute a date to IEEE/IANA. Earliest verifiable dated reference is RFC 790 (September 1981) [Confirmed blank] — IANA CSV; RFC 790

Related ports

the small-services cluster (7, 9, 13, 17, 19, 37); contrast port 18 (msp, Message Send Protocol — a distinct service); 29/udp sibling

Primary use

legacy Initial Connection Procedure for the MSG interprocess-communication facility of the National Software Works (NSW); RFC 790 labels port 29 "MSG-3 ICP" [29,RHT]

Other/unofficial uses

none verified; no known modern software binds to port 29 by default

Security implications

no known CVE, named trojan, or documented scanning campaign specifically targeting port 29; a generic "virus-flagged" note on some port-info sites appears to be boilerplate, not a verified attribution (absent from Trend Micro and Chebucto trojan-port tables); legacy well-known ports can generate IDS false positives

Typically seen on

rare; an open 29 suggests a legacy/unhardened host or scanner noise rather than a normal service [Likely]

Analyst note

Treat an open port 29 as a legacy reservation with no known modern use — deny-by-default and investigate as a possible unhardened host or scan artifact rather than a recognized service.

Port 29/udp is registered with IANA as msg-icp with the description "MSG ICP," assignee Robert Thomas, contact Robert Thomas, and a blank reference field. The same service is dual-registered on TCP: port 29/tcp carries the identical service name, description, and assignee, so the two are companion entries rather than distinct protocols. The assignment traces back to RFC 1700 (the October 1994 "Assigned Numbers" list), where the entry appears as "MSG ICP" attributed to Robert Thomas of BBN (Bolt, Beranek and Newman). RFC 1700 lists only the name and contact — it points to no protocol-specification RFC, and none is linked in the current IANA registry, so the underlying wire protocol is undocumented in any public standards text. The name most plausibly denotes an early internal BBN messaging or inter-process communication service ("MSG" being a BBN message-handling lineage), but that reading is inference from the name and assignee, not a sourced specification. For a present-day analyst, port 29 is effectively a dead entry: port-reference databases note that modern services do not bind to it by default and that MSG ICP is absent from contemporary software ecosystems. No CVEs, malware families, or threat-intelligence reports specific to 29/udp surfaced in public sources as of June 2026, and no scan-frequency data singled the port out. Because there is no known active listener, the port presents no application-layer attack surface on a typical host; any traffic to it is most likely opportunistic UDP background noise, and the ordinary hardening practice of blocking unused ports at the firewall applies as it would to any unneeded registered port. Note that MSG ICP is unrelated to the Internet Cache Protocol (ICP, RFC 2186/2187, port 3130) despite the shared "ICP" abbreviation.

IANA assignment

msg-icp — "MSG ICP"; reference (blank — no RFC cited in IANA registry); assignee Robert Thomas; contact Robert Thomas; dual-registered 29/tcp + 29/udp [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry (cached the IANA Service Name and Transport Protocol Port Number Registry line 66; TCP counterpart line 65)

Range class

well-known (0–1023) [Confirmed]

Registration / modification date

none recorded in the IANA registry (blank) [Confirmed] — cached IANA CSV line 66

Status

obsolete / legacy — characterized as rarely or never seen in operational networks; no known modern software consumer; not referenced in post-RFC-1700 IANA updates [Likely] — portsmaster.org, WMU well-known-ports list

Related ports

29/tcp (companion msg-icp registration); not to be confused with ICP/Internet Cache Protocol on 3130 (RFC 2186/2187)

Primary use

registered as "MSG ICP" (Message ICP), attributed to Robert Thomas (BBN) in RFC 1700 (October 1994); no protocol-specification RFC is linked; original purpose undocumented beyond the name — likely an early internal BBN messaging / inter-process communication service

Common software

none documented in public sources; modern services do not bind to port 29 by default and MSG ICP is absent from contemporary software ecosystems

Security implications

no CVEs, active malware campaigns, or threat-intel reports specific to 29/udp found as of June 2026; AuditMyPC records no current virus/trojan association; no known active service means no application-layer attack surface — exposure limited to opportunistic UDP sweeps; block unused ports at the firewall

Assignee contact

Robert Thomas (BBN — Bolt, Beranek and Newman), as listed in RFC 1700 [Confirmed] — RFC 1700

Scanning exposure

no scan-frequency data specific to 29/udp found in Shodan, Censys, or published internet-wide scan reports; the port is not on high-traffic or frequently targeted lists [Unknown] — Shodan exposure dashboard (no entry found)

Analyst note

a present-day open port 29 has no known legitimate service behind it; treat traffic as background noise or investigate as an anomaly. Underlying protocol is undocumented — do not assume behavior.