HTTPfy

Port 5191 (aol-1)

IANA assigns port 5191 to aol-1: AmericaOnline1.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
aol-1 TCP AmericaOnline1 Bruce Mackey -
aol-1 UDP AmericaOnline1 Bruce Mackey -

Check what is listening on port 5191

Linux: is anything listening on TCP 5191?
sudo ss -tlnp 'sport = :5191'
Linux: UDP 5191
sudo ss -ulnp 'sport = :5191'
Linux / macOS: which process owns the port
sudo lsof -nP -i :5191
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':5191 '
Windows (Command Prompt)
netstat -ano | findstr :5191
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 5191 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 5191
From Windows
Test-NetConnection HOST -Port 5191
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 5191

Block port 5191 in the firewall

ufw
sudo ufw deny 5191/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 5191 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 5191 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 5191' -Direction Inbound -Protocol TCP -LocalPort 5191 -Action Block
ufw
sudo ufw deny 5191/udp
iptables
sudo iptables -A INPUT -p udp --dport 5191 -j DROP
nftables
sudo nft add rule inet filter input udp dport 5191 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 5191' -Direction Inbound -Protocol UDP -LocalPort 5191 -Action Block

Related ports

5172pcoip-mgmt5190aol5192aol-25193aol-3

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.