Port 4827HTCP (Hypertext Caching Protocol)

HTCP lets HTTP caches query and manage peer caches, commonly over UDP on port 4827.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 2/10
lookups: 0

also known as Hypertext Caching Protocol, RFC 2756

Technical Details

what runs on :4827

HTCP (specified in RFC 2756) carries cache queries and management operations such as testing whether an object is cached or requesting that it be cleared. Implementations commonly exchange framed HTCP messages over UDP; the registry also assigns TCP, but that is not the transport most typically encountered. Squid commonly uses port 4827 for HTCP. This is distinct from HTTP client traffic, which normally uses ports 80 or 443.

Security Information

exposure of :4827

risk score

2/ 10safe

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

web services averages 3.1 across 192 ports — this one sits 1.1 below.

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

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

security overview

HTCP is not encrypted by default, and an exposed cache may reveal cache contents or metadata and accept cache-management requests, depending on its configuration. Do not expose it to the public internet; restrict it to trusted cache peers with firewall rules and the implementation's access controls.

Record

iana registry entry

port: :4827
service: HTCP (Hypertext Caching Protocol)
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 2/10safe
category: Web Services Network Services
usage: HTCP is a cache-to-cache protocol used by HTTP proxy caches, including Squid, to query peer caches and coordinate cache operations. Engineers are most likely to encounter it between configured proxy-cache peers, rather than on a public-facing service.
lookups: 0rank 993
added: 2026-10-06
updated: 2026-10-06
references: IANA service name registry — port 4827

Something wrong?

This record is maintained by the engineers who use port 4827. 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 2026-10-06.

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

all 192 in web services →

the 8 most looked-up other ports in web services — 192 ports carry that label.

port	service	proto	category	risk	views
:8888	Sun Answerbook & Alt HTTP	TCP	Web Services	caution	123.9k
:8000	Intel Remote Desktop / Alternate HTTP Port	TCP	Web Services	safe	84.3k
:8888	NewsEDGE	TCPUDP	Web Services	caution	83.3k
:8888	HTTP Alternative Port	TCP	Web Services	caution	76.5k
:8888	GNUmp3d Streaming HTTP	TCP	Web Services	caution	76.3k
:9080	Groove RPC	TCPUDP	Web Services	caution	70.8k
:8881	Atlasz Secure Server	TCP	Web Services	caution	67.6k
:80	HTTP	TCPUDP	Web Services	caution	67.3k

risk mix of the 8 listed

safe13%
caution88%

0 of 8 encrypted

Port :4827HTCP (Hypertext Caching Protocol)

Technical Details

Security Information

Related Ports

Port 4827HTCP (Hypertext Caching Protocol)