Port 3130Internet Cache Protocol v2

ICPv2 lets web-cache proxies query peer caches about whether they have a requested object.

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

also known as icpv2, ICP

Technical Details

what runs on :3130

ICPv2 (Internet Cache Protocol version 2, RFC 2186) coordinates web-cache hierarchies. A cache sends a query containing a URL to a peer and receives a response such as HIT or MISS; messages are compact and carry an opcode, request identifier, and URL. The protocol has no connection handshake and is conventionally sent as UDP datagrams on port 3130. IANA lists both TCP and UDP, but ordinary ICPv2 deployments use UDP. Squid commonly uses 3130 for ICP; this is separate from the HTTP proxy listener, often on port 3128.

Security Information

exposure of :3130

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 3.2 across 183 ports — this one sits 1.2 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

ICPv2 is unencrypted and does not authenticate peers, so cache operators should allow it only between explicitly trusted cache hosts, not expose it broadly to the internet. Unrestricted access can reveal cache-hit information and consume proxy resources; unauthenticated UDP also makes spoofed messages possible. It is cache-coordination traffic rather than a service intended for public clients.

Record

iana registry entry

port: :3130
service: Internet Cache Protocol v2
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 2/10safe
category: Web Services Network Services
usage: ICPv2 is used between cooperating web caches, notably Squid proxies, to ask whether a peer has a URL cached and receive a hit or miss response. Engineers typically encounter it as UDP traffic on port 3130 between cache peers, not as a client-facing web service.
lookups: 0rank 993
added: 2026-09-27
updated: 2026-09-27
references: IANA service name registry — port 3130

Something wrong?

This record is maintained by the engineers who use port 3130. 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 2026-09-27.

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edit this record →back to the registry

Related Ports

all 183 in web services →

the 8 most looked-up other ports in web services — 183 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 :3130Internet Cache Protocol v2

Technical Details

Security Information

Related Ports

Port 3130Internet Cache Protocol v2