Port 200 (src)

IANA assigns port 200 to src: IBM System Resource Controller.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference

src TCP IBM System Resource Controller Gerald McBrearty -

src UDP IBM System Resource Controller Gerald McBrearty -

Linux: is anything listening on TCP 200?

sudo ss -tlnp 'sport = :200'

Linux: UDP 200

sudo ss -ulnp 'sport = :200'

Linux / macOS: which process owns the port

sudo lsof -nP -i :200

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':200 '

Windows (Command Prompt)

netstat -ano | findstr :200

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 200 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 200

From Windows

Test-NetConnection HOST -Port 200

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 200

ufw

sudo ufw deny 200/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 200 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 200 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 200' -Direction Inbound -Protocol TCP -LocalPort 200 -Action Block

ufw

sudo ufw deny 200/udp

iptables

sudo iptables -A INPUT -p udp --dport 200 -j DROP

nftables

sudo nft add rule inet filter input udp dport 200 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 200' -Direction Inbound -Protocol UDP -LocalPort 200 -Action Block

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