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Port 3936 (mailprox)

IANA assigns port 3936 to mailprox: Mailprox.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
mailprox TCP Mailprox Christof Drescher -
mailprox UDP Mailprox Christof Drescher -

Registry dates for this port: registered 2003-11.

Check what is listening on port 3936

Linux: is anything listening on TCP 3936?
sudo ss -tlnp 'sport = :3936'
Linux: UDP 3936
sudo ss -ulnp 'sport = :3936'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3936
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3936 '
Windows (Command Prompt)
netstat -ano | findstr :3936
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3936 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3936
From Windows
Test-NetConnection HOST -Port 3936
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3936

Block port 3936 in the firewall

ufw
sudo ufw deny 3936/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3936 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3936 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3936' -Direction Inbound -Protocol TCP -LocalPort 3936 -Action Block
ufw
sudo ufw deny 3936/udp
iptables
sudo iptables -A INPUT -p udp --dport 3936 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3936 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3936' -Direction Inbound -Protocol UDP -LocalPort 3936 -Action Block

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3934sunfm-port3935sdp-portmapper3937dvbservdsc3938dbcontrol-agent, dbcontrol_agent

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