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Port 183 (ocbinder)

IANA assigns port 183 to ocbinder: OCBinder.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
ocbinder TCP OCBinder - -
ocbinder UDP OCBinder - -

Check what is listening on port 183

Linux: is anything listening on TCP 183?
sudo ss -tlnp 'sport = :183'
Linux: UDP 183
sudo ss -ulnp 'sport = :183'
Linux / macOS: which process owns the port
sudo lsof -nP -i :183
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':183 '
Windows (Command Prompt)
netstat -ano | findstr :183
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 183 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 183
From Windows
Test-NetConnection HOST -Port 183
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 183

Block port 183 in the firewall

ufw
sudo ufw deny 183/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 183 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 183 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 183' -Direction Inbound -Protocol TCP -LocalPort 183 -Action Block
ufw
sudo ufw deny 183/udp
iptables
sudo iptables -A INPUT -p udp --dport 183 -j DROP
nftables
sudo nft add rule inet filter input udp dport 183 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 183' -Direction Inbound -Protocol UDP -LocalPort 183 -Action Block

Related ports

181unify182audit184ocserver185remote-kis

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