Port 3540Microsoft Peer Name Resolution Protocol (PNRP)

PNRP lets Windows peer-to-peer applications publish and resolve peer names to network endpoints, typically over UDP 3540.

inNetwork Services System

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

also known as pnrp-port, PNRP, MS-PNRP

Technical Details

what runs on :3540

PNRP is a decentralized name-resolution protocol: peers publish peer names and endpoint information into a PNRP cloud, and other peers query that cloud to resolve names to network endpoints. The IANA assignment lists both TCP and UDP; normal Windows PNRP traffic is commonly UDP on port 3540 and uses IPv6, with tunneling such as Teredo possible in some configurations. PNRP is not DNS and does not encrypt traffic by default; secure peer names can use cryptographic identities and signatures to authenticate name records.

Security Information

exposure of :3540

risk score

2/ 10safe

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

network services averages 2.7 across 1,410 ports — this one sits 0.7 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

This is generally a legacy or feature-dependent Windows service, not a routine public server. If PNRP is not needed, disable the feature or block unsolicited inbound traffic; otherwise limit access to the networks where peer discovery is intended. PNRP does not provide transport encryption, and an exposed listener can receive peer-protocol traffic, but this port is not ordinarily associated with remote administration or a widely deployed internet-facing service.

Record

iana registry entry

port: :3540
service: Microsoft Peer Name Resolution Protocol (PNRP)
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 2/10safe
category: Network Services System
usage: This is the port associated with Microsoft's Peer Name Resolution Protocol, used by Windows peer-to-peer networking to find peers without relying on conventional DNS. Engineers are most likely to encounter it on Windows systems where legacy P2P features or applications are enabled; it is not commonly exposed as an internet-facing service.
lookups: 0rank 993
added: 2026-09-30
updated: 2026-09-30
references: IANA service name registry — port 3540

Something wrong?

This record is maintained by the engineers who use port 3540. 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 2026-09-30.

01edit any field on a page of its own
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edit this record →back to the registry

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all 1,410 in network services →

the 8 most looked-up other ports in network services — 1,410 ports carry that label.

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:3128	Tatsoft Default HTTP Proxy	TCP	Web Services	caution	46.8k

risk mix of the 8 listed

caution100%

0 of 8 encrypted

Port :3540Microsoft Peer Name Resolution Protocol (PNRP)

Technical Details

Security Information

Related Ports

Port 3540Microsoft Peer Name Resolution Protocol (PNRP)