HTTPfy

Port 653 (repscmd)

IANA assigns port 653 to repscmd: RepCmd.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
repscmd TCP RepCmd Scott Dale 2 -
repscmd UDP RepCmd Scott Dale 2 -

Check what is listening on port 653

Linux: is anything listening on TCP 653?
sudo ss -tlnp 'sport = :653'
Linux: UDP 653
sudo ss -ulnp 'sport = :653'
Linux / macOS: which process owns the port
sudo lsof -nP -i :653
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':653 '
Windows (Command Prompt)
netstat -ano | findstr :653
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 653 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 653
From Windows
Test-NetConnection HOST -Port 653
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 653

Block port 653 in the firewall

ufw
sudo ufw deny 653/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 653 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 653 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 653' -Direction Inbound -Protocol TCP -LocalPort 653 -Action Block
ufw
sudo ufw deny 653/udp
iptables
sudo iptables -A INPUT -p udp --dport 653 -j DROP
nftables
sudo nft add rule inet filter input udp dport 653 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 653' -Direction Inbound -Protocol UDP -LocalPort 653 -Action Block

Related ports

651ieee-mms652hello-port654aodv655tinc

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