Port 191Prospero Directory Service

Prospero provides distributed directory and file-system lookup services over TCP or UDP.

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

Technical Details

what runs on :191

Prospero supports directory-service exchanges over both TCP and UDP, using requests and responses to retrieve directory entries, attributes, and references to resources. It was designed for distributed namespace and file-system access, with directory information able to lead clients to other services or locations. It is normally identified by service name rather than by a modern application protocol stack, and deployments are uncommon today.

Security Information

exposure of :191

risk score

1/ 10safe

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

file transfer averages 4.0 across 125 ports — this one sits 3.0 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

Prospero traffic is not encrypted by default. An exposed legacy instance may disclose directory structure and exported resources, so it should generally be restricted to trusted networks and monitored for unexpected requests; its rarity makes accidental exposure more likely than widespread automated exploitation.

Record

iana registry entry

port: :191
service: Prospero Directory Service
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 1/10safe
category: File Transfer Network Services
usage: Prospero is an older distributed directory service and virtual file-system protocol associated with B. Clifford Neuman and USC ISI. Engineers are most likely to encounter it on legacy research, academic, or archival systems rather than modern deployments.
lookups: 0rank 994
added: 2026-08-22
updated: 2026-08-22
references: IANA service name registry — port 191

Something wrong?

This record is maintained by the engineers who use port 191. 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 2026-08-22.

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Related Ports

all 125 in file transfer →

the 8 most looked-up other ports in file transfer — 125 ports carry that label.

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:548	Apple Filing Protocol	TCP	File Transfer	caution	36.8k
:7000	Vuze HTTPS Tracker	TCPtls	Security	caution	28.9k
:1337	PowerFolder P2P	TCP	Security	caution	27.1k
:9001	SharePoint Authoring		Web Services	caution	26.3k
:8080	FilePhile Relay	UDP	File Transfer	caution	25.6k
:1337	WASTE Encrypted Sharing	TCP	Security	caution	22.9k

risk mix of the 8 listed

caution100%

1 of 8 encrypted

Port :191Prospero Directory Service

Technical Details

Security Information

Related Ports

Port 191Prospero Directory Service