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Port 29 (msg-icp)

IANA assigns port 29 to msg-icp: MSG ICP.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
msg-icp TCP MSG ICP Robert Thomas -
msg-icp UDP MSG ICP Robert Thomas -

Check what is listening on port 29

Linux: is anything listening on TCP 29?
sudo ss -tlnp 'sport = :29'
Linux: UDP 29
sudo ss -ulnp 'sport = :29'
Linux / macOS: which process owns the port
sudo lsof -nP -i :29
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':29 '
Windows (Command Prompt)
netstat -ano | findstr :29
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 29 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 29
From Windows
Test-NetConnection HOST -Port 29
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 29

Block port 29 in the firewall

ufw
sudo ufw deny 29/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 29 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 29 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 29' -Direction Inbound -Protocol TCP -LocalPort 29 -Action Block
ufw
sudo ufw deny 29/udp
iptables
sudo iptables -A INPUT -p udp --dport 29 -j DROP
nftables
sudo nft add rule inet filter input udp dport 29 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 29' -Direction Inbound -Protocol UDP -LocalPort 29 -Action Block

Related ports

25SMTP27nsw-fe31msg-auth33dsp

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