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Port 3733 (multip-msg)

IANA assigns port 3733 to multip-msg: Multipuesto Msg Port.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
multip-msg TCP Multipuesto Msg Port Felisa Ares -
multip-msg UDP Multipuesto Msg Port Felisa Ares -

Registry dates for this port: registered 2003-04.

Check what is listening on port 3733

Linux: is anything listening on TCP 3733?
sudo ss -tlnp 'sport = :3733'
Linux: UDP 3733
sudo ss -ulnp 'sport = :3733'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3733
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3733 '
Windows (Command Prompt)
netstat -ano | findstr :3733
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3733 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3733
From Windows
Test-NetConnection HOST -Port 3733
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3733

Block port 3733 in the firewall

ufw
sudo ufw deny 3733/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3733 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3733 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3733' -Direction Inbound -Protocol TCP -LocalPort 3733 -Action Block
ufw
sudo ufw deny 3733/udp
iptables
sudo iptables -A INPUT -p udp --dport 3733 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3733 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3733' -Direction Inbound -Protocol UDP -LocalPort 3733 -Action Block

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3731smap3732m-wnn3734synel-data3735pwdis

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