Port 1723 (PPTP)

Point-to-Point Tunneling Protocol VPN (control channel; data uses GRE, IP protocol 47).

Registered (user) port, 1024-49151 TCP VPN Do not expose to the internet

What port 1723 is used for

Point-to-Point Tunneling Protocol VPN (control channel; data uses GRE, IP protocol 47).

Security: should port 1723 be open?

Do not expose to the internet. PPTP's MS-CHAPv2 authentication is broken and can be cracked; do not use it. Replace with WireGuard, OpenVPN or IKEv2.

IANA assignment

Service nameProtoDescriptionAssigneeReference

pptp TCP pptp Ken Crocker RFC 2637

pptp UDP pptp Ken Crocker RFC 2637

Registry dates for this port: last modified 2021-09-21.

Check what is listening on port 1723

Linux: is anything listening on TCP 1723?

sudo ss -tlnp 'sport = :1723'

Linux / macOS: which process owns the port

sudo lsof -nP -i :1723

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':1723 '

Windows (Command Prompt)

netstat -ano | findstr :1723

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 1723 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine

nc -vz -w 5 HOST 1723

From Windows

Test-NetConnection HOST -Port 1723

Block port 1723 in the firewall

ufw

sudo ufw deny 1723/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 1723 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 1723 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 1723' -Direction Inbound -Protocol TCP -LocalPort 1723 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.