HTTPfy

Port 641 (repcmd)

IANA assigns port 641 to repcmd.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
repcmd TCP repcmd Scott Dale -
repcmd UDP repcmd Scott Dale -

Check what is listening on port 641

Linux: is anything listening on TCP 641?
sudo ss -tlnp 'sport = :641'
Linux: UDP 641
sudo ss -ulnp 'sport = :641'
Linux / macOS: which process owns the port
sudo lsof -nP -i :641
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':641 '
Windows (Command Prompt)
netstat -ano | findstr :641
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 641 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 641
From Windows
Test-NetConnection HOST -Port 641
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 641

Block port 641 in the firewall

ufw
sudo ufw deny 641/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 641 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 641 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 641' -Direction Inbound -Protocol TCP -LocalPort 641 -Action Block
ufw
sudo ufw deny 641/udp
iptables
sudo iptables -A INPUT -p udp --dport 641 -j DROP
nftables
sudo nft add rule inet filter input udp dport 641 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 641' -Direction Inbound -Protocol UDP -LocalPort 641 -Action Block

Related ports

639msdp640entrust-sps642esro-emsdp643sanity

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