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// Other services

Port 5053: RLM License Server

Port 5053 is assigned by IANA to rlm (RLM License Server), rlm-disc (RLM Discovery Server).

5053

How rlm works

Other services
client:5053rlmresponse client:5053rlmresponse

The client sends a request to port 5053 and the rlm service answers.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned2 registered services
Range
Registered (1024-49151)
Category
Other services
01 Security

Is port 5053 dangerous?

We have no specific security note for port 5053. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 5053

ServicePortTransportDescriptionReferenceUpdated
rlm 5053 TCP RLM License Server - 2008-07-28
rlm-disc 5053 UDP RLM Discovery Server - 2012-11-06

// source: IANA service name and port number registry

03 Check it

Which program uses port 5053, and is it reachable?

Linux

sudo ss -ltnup 'sport = :5053'      # process listening on 5053
sudo lsof -nP -i :5053

macOS

sudo lsof -nP -i :5053

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5053 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 5053
netstat -ano | findstr :5053

From another machine

nmap -p 5053 -sV <host>
sudo nmap -sU -p 5053 <host>
nc -zv <host> 5053

Block it in the firewall

sudo ufw deny 5053/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 5053" -Direction Inbound -LocalPort 5053 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 5053 used for?

Port 5053 is assigned by IANA to rlm (RLM License Server), rlm-disc (RLM Discovery Server).

Is port 5053 TCP or UDP?

Port 5053 is registered for TCP and UDP.

Is it safe to open port 5053?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Close the port if nothing on the host needs it.

How do I check if port 5053 is open?

On Linux run "ss -ltnup 'sport = :5053'", on macOS "lsof -nP -i :5053", and on Windows "netstat -ano | findstr :5053" to see the local process. From another machine, "nmap -p 5053 <host>" shows whether it is reachable.

05 Related
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