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Port 45 (mpm)

IANA assigns port 45 to mpm: Message Processing Module [recv].

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
mpm TCP Message Processing Module [recv] - -
mpm UDP Message Processing Module [recv] - -

Check what is listening on port 45

Linux: is anything listening on TCP 45?
sudo ss -tlnp 'sport = :45'
Linux: UDP 45
sudo ss -ulnp 'sport = :45'
Linux / macOS: which process owns the port
sudo lsof -nP -i :45
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':45 '
Windows (Command Prompt)
netstat -ano | findstr :45
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 45 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 45
From Windows
Test-NetConnection HOST -Port 45
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 45

Block port 45 in the firewall

ufw
sudo ufw deny 45/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 45 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 45 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 45' -Direction Inbound -Protocol TCP -LocalPort 45 -Action Block
ufw
sudo ufw deny 45/udp
iptables
sudo iptables -A INPUT -p udp --dport 45 -j DROP
nftables
sudo nft add rule inet filter input udp dport 45 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 45' -Direction Inbound -Protocol UDP -LocalPort 45 -Action Block

Related ports

43nicname44mpm-flags46mpm-snd48auditd

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