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Port 731 (netviewdm3)

IANA assigns port 731 to netviewdm3: IBM NetView DM/6000 receive/tcp.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
netviewdm3 TCP IBM NetView DM/6000 receive/tcp Philippe Binet -
netviewdm3 UDP IBM NetView DM/6000 receive/tcp Philippe Binet -

Check what is listening on port 731

Linux: is anything listening on TCP 731?
sudo ss -tlnp 'sport = :731'
Linux: UDP 731
sudo ss -ulnp 'sport = :731'
Linux / macOS: which process owns the port
sudo lsof -nP -i :731
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':731 '
Windows (Command Prompt)
netstat -ano | findstr :731
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 731 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 731
From Windows
Test-NetConnection HOST -Port 731
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 731

Block port 731 in the firewall

ufw
sudo ufw deny 731/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 731 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 731 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 731' -Direction Inbound -Protocol TCP -LocalPort 731 -Action Block
ufw
sudo ufw deny 731/udp
iptables
sudo iptables -A INPUT -p udp --dport 731 -j DROP
nftables
sudo nft add rule inet filter input udp dport 731 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 731' -Direction Inbound -Protocol UDP -LocalPort 731 -Action Block

Related ports

729netviewdm1730netviewdm2741netgw742netrcs

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