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// Other services

Port 5191: AmericaOnline1

Port 5191 is assigned by IANA to aol-1 (AmericaOnline1).

5191

How aol-1 works

Other services
client:5191aol-1response client:5191aol-1response

The client sends a request to port 5191 and the aol-1 service answers.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Other services
01 Security

Is port 5191 dangerous?

We have no specific security note for port 5191. 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 5191

ServicePortTransportDescriptionReferenceUpdated
aol-1 5191 TCP, UDP AmericaOnline1 - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 5191, and is it reachable?

Linux

sudo ss -ltnup 'sport = :5191'      # process listening on 5191
sudo lsof -nP -i :5191

macOS

sudo lsof -nP -i :5191

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5191 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 5191
netstat -ano | findstr :5191

From another machine

nmap -p 5191 -sV <host>
sudo nmap -sU -p 5191 <host>
nc -zv <host> 5191

Block it in the firewall

sudo ufw deny 5191/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 5191" -Direction Inbound -LocalPort 5191 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 5191 used for?

Port 5191 is assigned by IANA to aol-1 (AmericaOnline1).

Is port 5191 TCP or UDP?

Port 5191 is registered for TCP and UDP.

Is it safe to open port 5191?

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 5191 is open?

On Linux run "ss -ltnup 'sport = :5191'", on macOS "lsof -nP -i :5191", and on Windows "netstat -ano | findstr :5191" to see the local process. From another machine, "nmap -p 5191 <host>" shows whether it is reachable.

05 Related
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