Port 39Resource Location Protocol
Resource Location Protocol (RLP) enables networked devices to identify and locate resources unambiguously within a distributed computing environment. It facilitates efficient querying and retrieval of network resource information, making it easier for systems to manage connections and communicate with each other dynamically..
- transport
- tcp · udp
- in transit
- cleartext
- assignment
- official
- risk
- 4/10
- lookups
- 10,605
2 transports registered
payload readable on path
registered with iana
caution
rank 411 of 993 · top 41%
Technical Details
what runs on :39Resource Location Protocol (RLP) is designed to allow computers within a network to locate various resources, such as services or data repositories. It enables clients to broadcast queries and receive unambiguous responses pointing to the precise location of network resources, simplifying resource management in distributed systems.
RLP operates over both TCP and UDP on port 39, offering flexibility depending on the network environment—UDP for lightweight, low latency requests, and TCP for reliable, connection-oriented communication. The protocol supports resource identification through unique naming conventions and typically forms part of early network service discovery stacks.
While not widely used in modern architectures, RLP historically played a role in early network environments to facilitate dynamic resource lookup before technologies like DNS or more advanced discovery protocols were standardized. Due to its simplicity, it remains relevant in certain legacy or specialized network setups.
Security Information
exposure of :39risk score
4/ 10caution
worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.
network services averages 3.9 across 604 ports — this one sits 0.1 above.
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
Common vulnerabilities associated with RLP include:
- Susceptibility to spoofing attacks where an attacker responds to RLP queries with false information, redirecting clients to malicious endpoints.
- Denial of Service (DoS) possibilities if attackers flood the service with excessive resource location requests.
- Lack of encryption or authentication, leading to potential eavesdropping or data tampering.
Mitigations involve:
- Restricting access to port 39 at network perimeters to trusted hosts only.
- Applying firewalls or access control lists (ACLs) to prevent unsolicited external RLP traffic.
- Implementing network monitoring to detect abnormal query patterns.
- Transitioning to modern, secure service discovery protocols that support encryption and authentication when possible.
Related Ports
the 8 most looked-up other ports in network services — 604 ports carry that label.
| port | service | risk | |||
|---|---|---|---|---|---|
| :9080 | Groove RPC | TCPUDP | Web Services | caution | 70.8k |
| :6543 | Jetnet | UDP | Network Services | caution | 65.3k |
| :5938 | TeamViewer | TCPUDP | Remote Access | caution | 65.0k |
| :8291 | Winbox MikroTik Admin | TCP | Security | caution | 62.9k |
| :3233 | WhiskerControl Protocol | TCPUDP | Network Services | caution | 61.9k |
| :3268 | Microsoft Global Catalog (GC) | TCPUDP | Security | caution | 54.6k |
| :135 | Microsoft EPMAP | TCPUDP | Security | caution | 51.9k |
| :3128 | Tatsoft Default HTTP Proxy | TCP | Web Services | caution | 46.8k |
risk mix of the 8 listed
- caution100%
0 of 8 encrypted