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Port 3311 (mcns-tel-ret)

IANA assigns port 3311 to mcns-tel-ret: MCNS Tel Ret.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
mcns-tel-ret TCP MCNS Tel Ret Randall Atkinson -
mcns-tel-ret UDP MCNS Tel Ret Randall Atkinson -

Check what is listening on port 3311

Linux: is anything listening on TCP 3311?
sudo ss -tlnp 'sport = :3311'
Linux: UDP 3311
sudo ss -ulnp 'sport = :3311'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3311
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3311 '
Windows (Command Prompt)
netstat -ano | findstr :3311
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3311 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3311
From Windows
Test-NetConnection HOST -Port 3311
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3311

Block port 3311 in the firewall

ufw
sudo ufw deny 3311/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3311 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3311 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3311' -Direction Inbound -Protocol TCP -LocalPort 3311 -Action Block
ufw
sudo ufw deny 3311/udp
iptables
sudo iptables -A INPUT -p udp --dport 3311 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3311 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3311' -Direction Inbound -Protocol UDP -LocalPort 3311 -Action Block

Related ports

3309tns-adv3310dyna-access3312appman-server3313uorb

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