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Port 3684 (faxstfx-port)

IANA assigns port 3684 to faxstfx-port: FAXstfX.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
faxstfx-port TCP FAXstfX Alec Carlson -
faxstfx-port UDP FAXstfX Alec Carlson -

Registry dates for this port: registered 2003-01.

Check what is listening on port 3684

Linux: is anything listening on TCP 3684?
sudo ss -tlnp 'sport = :3684'
Linux: UDP 3684
sudo ss -ulnp 'sport = :3684'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3684
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3684 '
Windows (Command Prompt)
netstat -ano | findstr :3684
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3684 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3684
From Windows
Test-NetConnection HOST -Port 3684
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3684

Block port 3684 in the firewall

ufw
sudo ufw deny 3684/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3684 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3684 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3684' -Direction Inbound -Protocol TCP -LocalPort 3684 -Action Block
ufw
sudo ufw deny 3684/udp
iptables
sudo iptables -A INPUT -p udp --dport 3684 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3684 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3684' -Direction Inbound -Protocol UDP -LocalPort 3684 -Action Block

Related ports

3682cas-mapi3683bmc-ea3685dsx-agent3686tnmpv2

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