HTTPfy

Port 128 (gss-xlicen)

IANA assigns port 128 to gss-xlicen: GSS X License Verification.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
gss-xlicen TCP GSS X License Verification John Light -
gss-xlicen UDP GSS X License Verification John Light -

Check what is listening on port 128

Linux: is anything listening on TCP 128?
sudo ss -tlnp 'sport = :128'
Linux: UDP 128
sudo ss -ulnp 'sport = :128'
Linux / macOS: which process owns the port
sudo lsof -nP -i :128
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':128 '
Windows (Command Prompt)
netstat -ano | findstr :128
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 128 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 128
From Windows
Test-NetConnection HOST -Port 128
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 128

Block port 128 in the firewall

ufw
sudo ufw deny 128/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 128 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 128 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 128' -Direction Inbound -Protocol TCP -LocalPort 128 -Action Block
ufw
sudo ufw deny 128/udp
iptables
sudo iptables -A INPUT -p udp --dport 128 -j DROP
nftables
sudo nft add rule inet filter input udp dport 128 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 128' -Direction Inbound -Protocol UDP -LocalPort 128 -Action Block

Related ports

126nxedit127locus-con129pwdgen130cisco-fna

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