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Port 3858 (trap-port-mom)

IANA assigns port 3858 to trap-port-mom: Trap Port MOM.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
trap-port-mom TCP Trap Port MOM Norm Freedman -
trap-port-mom UDP Trap Port MOM Norm Freedman -

Registry dates for this port: registered 2003-08.

Check what is listening on port 3858

Linux: is anything listening on TCP 3858?
sudo ss -tlnp 'sport = :3858'
Linux: UDP 3858
sudo ss -ulnp 'sport = :3858'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3858
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3858 '
Windows (Command Prompt)
netstat -ano | findstr :3858
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3858 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3858
From Windows
Test-NetConnection HOST -Port 3858
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3858

Block port 3858 in the firewall

ufw
sudo ufw deny 3858/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3858 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3858 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3858' -Direction Inbound -Protocol TCP -LocalPort 3858 -Action Block
ufw
sudo ufw deny 3858/udp
iptables
sudo iptables -A INPUT -p udp --dport 3858 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3858 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3858' -Direction Inbound -Protocol UDP -LocalPort 3858 -Action Block

Related ports

3856informer3857trap-port3859nav-port3860sasp

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