- 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.
Port 4391: American Printware IMServer Protocol
Port 4391 is assigned by IANA to apwi-imserver (American Printware IMServer Protocol).
4391
How apwi-imserver works
Other servicesThe client sends a request to port 4391 and the apwi-imserver service answers.
- Transport
- TCP
- 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
Is port 4391 dangerous?
We have no specific security note for port 4391. Its risk depends on the program actually listening on it. General advice for other services services:
IANA registry entries for port 4391
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| apwi-imserver | 4391 | TCP | American Printware IMServer Protocol | - | 2009-02-12 |
| - | 4391 | - | Reserved | - | - |
// source: IANA service name and port number registry
Which program uses port 4391, and is it reachable?
Linux
sudo ss -ltnup 'sport = :4391' # process listening on 4391
sudo lsof -nP -i :4391macOS
sudo lsof -nP -i :4391
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4391 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 4391 netstat -ano | findstr :4391
From another machine
nmap -p 4391 -sV <host> nc -zv <host> 4391
Block it in the firewall
sudo ufw deny 4391/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 4391" -Direction Inbound -LocalPort 4391 -Protocol TCP -Action Block # Windows
What is port 4391 used for?
Port 4391 is assigned by IANA to apwi-imserver (American Printware IMServer Protocol).
Is port 4391 TCP or UDP?
Port 4391 is registered for TCP.
Is it safe to open port 4391?
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 4391 is open?
On Linux run "ss -ltnup 'sport = :4391'", on macOS "lsof -nP -i :4391", and on Windows "netstat -ano | findstr :4391" to see the local process. From another machine, "nmap -p 4391 <host>" shows whether it is reachable.
Other other services ports
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp