HTTPfy

Port 8991 (https-wmap)

IANA assigns port 8991 to https-wmap: webmail HTTPS service.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
https-wmap TCP webmail HTTPS service Chris Newman -
https-wmap UDP webmail HTTPS service Chris Newman -

Registry dates for this port: registered 2007-12-03.

Check what is listening on port 8991

Linux: is anything listening on TCP 8991?
sudo ss -tlnp 'sport = :8991'
Linux: UDP 8991
sudo ss -ulnp 'sport = :8991'
Linux / macOS: which process owns the port
sudo lsof -nP -i :8991
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':8991 '
Windows (Command Prompt)
netstat -ano | findstr :8991
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 8991 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 8991
From Windows
Test-NetConnection HOST -Port 8991
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 8991

Block port 8991 in the firewall

ufw
sudo ufw deny 8991/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 8991 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 8991 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 8991' -Direction Inbound -Protocol TCP -LocalPort 8991 -Action Block
ufw
sudo ufw deny 8991/udp
iptables
sudo iptables -A INPUT -p udp --dport 8991 -j DROP
nftables
sudo nft add rule inet filter input udp dport 8991 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 8991' -Direction Inbound -Protocol UDP -LocalPort 8991 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.