HTTPfy

Port 8901 (jmb-cds2)

IANA assigns port 8901 to jmb-cds2: JMB-CDS 2.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
jmb-cds2 TCP JMB-CDS 2 Curtis Bray -
jmb-cds2 UDP JMB-CDS 2 Curtis Bray -

Check what is listening on port 8901

Linux: is anything listening on TCP 8901?
sudo ss -tlnp 'sport = :8901'
Linux: UDP 8901
sudo ss -ulnp 'sport = :8901'
Linux / macOS: which process owns the port
sudo lsof -nP -i :8901
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':8901 '
Windows (Command Prompt)
netstat -ano | findstr :8901
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 8901 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 8901
From Windows
Test-NetConnection HOST -Port 8901
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 8901

Block port 8901 in the firewall

ufw
sudo ufw deny 8901/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 8901 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 8901 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 8901' -Direction Inbound -Protocol TCP -LocalPort 8901 -Action Block
ufw
sudo ufw deny 8901/udp
iptables
sudo iptables -A INPUT -p udp --dport 8901 -j DROP
nftables
sudo nft add rule inet filter input udp dport 8901 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 8901' -Direction Inbound -Protocol UDP -LocalPort 8901 -Action Block

Related ports

8899ospf-lite8900jmb-cds18908dpp8910manyone-http

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