71

Port 71/tcp is registered with IANA as netrjs-1 with the description "Remote Job Service" and a blank reference field; the same name and description are dual-registered on 71/udp, and every optional column in the registry (Assignee, Contact, Registration Date, Modification Date, Reference, Service Code, Unauthorized Use Reported, Assignment Notes) is blank. The port belongs to the NETRJS (Network Remote Job Entry Service) suite that occupies ports 71–74, an ARPANET-era protocol for submitting batch jobs to IBM mainframes from remote hosts. Port 71 specifically served as the contact socket: a client opened an Initial Connection Protocol (ICP) connection to socket 71 to establish a Telnet-style operator console channel, and from that console the server spawned the subsequent simplex data-transfer channels — card reader, line printer, and card punch — at fixed offsets on the neighboring ports. Users submitted Job Control Language (JCL), monitored job status, and retrieved print and punch output through this console connection. The protocol is documented in RFC 740 (NETRJS Protocol, 1977), with earlier specifications in RFC 88 (1971) and RFC 325 (1972); CCN's RJS software at UCLA was the reference implementation. For an analyst, port 71 is effectively a historical curiosity: the NETRJS protocol is fully obsolete, no modern software is known to use it, and there is no documented internet exposure, no associated CVE, and no known malware channel. The blank IANA reference field is recorded honestly — the registry cites no RFC for this entry, so none is fabricated. A responsive port 71 on a modern host is therefore anomalous and worth investigating as a non-standard service, decoy, or backdoor rather than a legitimate NETRJS deployment.

IANA assignment

netrjs-1 — "Remote Job Service"; reference (blank — no RFC cited in IANA registry); assignee (blank); dual-registered 71/tcp + 71/udp [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry (the IANA Service Name and Transport Protocol Port Number Registry lines 166–167)

Range class

well-known / System Ports (0–1023) [Confirmed] — IANA registry

Related ports

72/tcp, 73/tcp, 74/tcp (rest of the NETRJS suite — data-transfer channels)

Primary use

ARPANET-era remote batch job submission to IBM mainframes via NETRJS; port 71 is the contact socket for the Telnet-style operator console channel, from which card-reader/printer/punch data channels are spawned. Effectively obsolete; no known active deployments

Protocol lineage

NETRJS suite, ports 71–74; defined in RFC 740 (1977), earlier RFC 88 (1971) and RFC 325 (1972)

Common software

CCN's RJS (Remote Job Service) mainframe software (UCLA, ARPANET era); no modern software known to use this port

Security implications

no CVEs or documented vulnerabilities; protocol predates modern TCP/IP security concerns; no significant scanning activity or internet-exposed NETRJS hosts documented; not a known malware channel. Internet exposure assessed as negligible given complete obsolescence (no specific scan data found)

Typically seen on

nothing in modern infrastructure; a responsive port 71 is anomalous and worth investigating

Analyst note

NETRJS is fully obsolete. An open port 71 is statistically rare and not a normal modern service — treat as an anomaly, decoy, or backdoor and investigate.

Port 71/udp is registered with IANA as netrjs-1 with the description "Remote Job Service" and a blank reference field; the same name is dual-registered on 71/tcp at the adjacent registry row, with every optional column (assignee, contact, registration date, modification date, reference) left blank. The entry is one of four consecutive ports — 71 through 74, netrjs-1 through netrjs-4 — set aside for NETRJS, a Network Remote Job Service developed by the UCLA Campus Computing Network (CCN) to submit card-image batch jobs to an IBM 360 Model 91 over the ARPANET. The protocol is documented in RFC 740 (R. Braden, November 1977), which obsoleted RFCs 189 and 599; it defines "virtual remote batch terminals" with separate logical connections for an operator console (Telnet-based), a card reader, a line printer, and a card punch. The four port numbers distinguished character sets: port 71 was the EBCDIC endpoint, with sibling assignments covering ASCII-68 and ASCII-63 variants. NETRJS is now a historic protocol with no modern implementations: it belongs to the same Remote Job Entry (RJE) family as mainframe batch submission, but no current commercial or open-source software ships it. For an analyst, a responsive port 71 is essentially never a legitimate NETRJS service. Note one nuance worth recording honestly: RFC 740 describes TCP-only operation, so while IANA carries the 71/udp assignment, the UDP transport was never standardized with a protocol specification — the registry reserves the number but no document defines NETRJS-over-UDP. There are no CVEs or notable internet-scan exposure (Shodan/Censys) for port 71/udp, and standard perimeter hardening that blocks unused legacy well-known ports covers it.

IANA assignment

netrjs-1 — "Remote Job Service"; reference (blank — no RFC cited in IANA registry); assignee/contact/dates blank; dual-registered 71/tcp + 71/udp [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry (the IANA Service Name and Transport Protocol Port Number Registry, line 167; 71/tcp at line 166)

Range class

well-known (0–1023) [Confirmed]

Status

historic / obsolete; no modern implementations; IANA retains the assignment [Confirmed] — RFC 740 (historic)

Related ports

71–74 (netrjs-1 through netrjs-4); the broader Remote Job Entry (RJE) family

Primary use

NETRJS Remote Job Service — ARPANET-era batch job submission to IBM mainframes (UCLA CCN), one of four ports (71–74) by character set; port 71 = EBCDIC endpoint

Common software

none known current; original UCLA CCN implementation for ARPANET IBM mainframe use (~1971–1980s)

Security implications

no documented CVEs; no notable Shodan/Censys exposure; original protocol used only short terminal-ID/password auth with no encryption, but is effectively extinct; perimeter blocking of legacy well-known ports covers it

UDP caveat

RFC 740 describes TCP-only operation; 71/udp assignment exists in the registry but NETRJS-over-UDP was never standardized [Confirmed] — RFC 740, IANA registry

Reference reading

Wikipedia "Remote job entry" (no dedicated NETRJS page) [Likely] — en.wikipedia.org/wiki/Remote_job_entry

Analyst note

A responsive port 71 is not a normal modern service; treat as an anomaly worth investigating rather than legitimate NETRJS.