Port 1021RFC 3692-style Experiment 1

Reserved for RFC 3692-style protocol experiments on TCP, UDP, and SCTP.

transport: tcp · udp · sctp
in transit: cleartext
assignment: official
risk: 1/10
lookups: 0

also known as exp1

Technical Details

what runs on :1021

This port has no defined application protocol, handshake, message framing, or default payload. It is designated for experimental use on TCP, UDP, and SCTP; the behavior depends entirely on the experiment using it. A listener on port 1021 should therefore be identified by its application or process rather than assumed to implement a common service.

Security Information

exposure of :1021

risk score

1/ 10safe

routine exposure. this port is rarely the way in on its own — keep it patched and logged and move on.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp · sctp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

The port has no inherent security weakness because it specifies no protocol. Internet exposure is generally unnecessary and should be avoided unless the experiment explicitly requires it; assess the actual listener for unauthenticated access, cleartext data, and implementation-specific vulnerabilities.

Record

iana registry entry

port: :1021
service: RFC 3692-style Experiment 1
transport: TCPUDPSCTP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: uncategorised
usage: Port 1021 is reserved for RFC 3692-style protocol experiments under IESG stewardship. Engineers may encounter a temporary test implementation listening on TCP, UDP, or SCTP, but there is no default production service associated with it.
lookups: 0rank 993
added: 2026-08-20
updated: 2026-09-22
references: IANA service name registry — port 1021
RFC 4727
RFC 6335

Something wrong?

This record is maintained by the engineers who use port 1021. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-09-22.

01edit any field on a page of its own
02a model checks it for accuracy and spam
03clean and confident goes live immediately

edit this record →back to the registry

Related Ports

browse categories →

ports registered around :1021, by lookups.

port	service	proto	category	risk	views
:981	Check Point Embedded HTTPS Management	TCPtls	Security	caution	28.5k
:992	Telnet over TLS/SSL	TCPUDPtls	Security	caution	23.5k
:989	FTPS Data	TCPUDPtls	Security	caution	22.5k
:990	FTPS Control	TCPUDPtls	Security	caution	21.8k
:995	POP3S	TCPtls	Email	caution	18.8k
:991	Netnews Administration System	TCPUDP	Network Services	caution	17.9k
:1080	SOCKS Proxy	TCPtls	Security	caution	16.1k
:1059	IBM AIX NIM	TCPUDP	Network Services	caution	15.6k

risk mix of the 8 listed

caution100%

6 of 8 encrypted

Port :1021RFC 3692-style Experiment 1

Technical Details

Security Information

Related Ports

Port 1021RFC 3692-style Experiment 1