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Port 400 (osb-sd)

IANA assigns port 400 to osb-sd: Oracle Secure Backup.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
osb-sd TCP Oracle Secure Backup
Formerly was Workstation Solutions Steven Wertheimer -
osb-sd UDP Oracle Secure Backup
Formerly was Workstation Solutions Steven Wertheimer -

Registry dates for this port: registered 2008-06-06, last modified 2023-12-27.

Check what is listening on port 400

Linux: is anything listening on TCP 400?
sudo ss -tlnp 'sport = :400'
Linux: UDP 400
sudo ss -ulnp 'sport = :400'
Linux / macOS: which process owns the port
sudo lsof -nP -i :400
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':400 '
Windows (Command Prompt)
netstat -ano | findstr :400
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 400 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 400
From Windows
Test-NetConnection HOST -Port 400
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 400

Block port 400 in the firewall

ufw
sudo ufw deny 400/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 400 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 400 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 400' -Direction Inbound -Protocol TCP -LocalPort 400 -Action Block
ufw
sudo ufw deny 400/udp
iptables
sudo iptables -A INPUT -p udp --dport 400 -j DROP
nftables
sudo nft add rule inet filter input udp dport 400 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 400' -Direction Inbound -Protocol UDP -LocalPort 400 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.