Port 1723 PPTP
Port 1723 is the IANA-assigned pptp port for pptp (TCP / UDP).
What is port 1723 used for?
Port 1723 is assigned to pptp and uses TCP / UDP. The IANA registry describes the service as “pptp”. It sits in the registered range, the block used by databases, application servers and developer tooling. Port conflicts here are common when several local services start at once.
Ports are the transport-layer address a service listens on. A client that wants to reach pptp connects to port 1723. A TCP connection is refused when nothing is listening, while a UDP request simply goes unanswered. That is why a port conflict appears whenever two processes try to bind the same number.
Use the commands below to confirm whether port 1723 is actually in use before you change firewall rules. Blocking the port stops new inbound traffic at the firewall, but it does not stop a local process from listening, and it does not remove the service from the machine.
Browse all VPN and tunnelling ports
Source: IANA Service Name and Transport Protocol Port Number Registry. Registered assignee: [Ken_Crocker]. Reference: [RFC 2637].
Check and block port 1723
Copy-ready commands for the protocols assigned to this port. Run the check first, then block only what should not be reachable.
Check on Linux
sudo ss -tlpn 'sport = :1723'
sudo ss -ulpn 'sport = :1723'Check on Windows
Get-NetTCPConnection -LocalPort 1723 -State Listen -ErrorAction SilentlyContinue
Get-NetUDPEndpoint -LocalPort 1723 -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 1723/tcp
sudo ufw deny 1723/udpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 1723 -j DROP
sudo iptables -A INPUT -p udp --dport 1723 -j DROPThese commands are examples for a typical host. Check the listener before you change firewall rules, and persist iptables rules with iptables-save or netfilter-persistent. On Windows, use Windows Defender Firewall or New-NetFirewallRule for persistent blocks. The iptables rules here cover IPv4; mirror them with ip6tables if IPv6 is enabled.
Is port 1723 safe to expose?
PPTP's MS-CHAPv2 authentication is cryptographically broken and the protocol is obsolete. Replace it with WireGuard, OpenVPN or IPsec. Treat this port as sensitive. Restrict it to trusted networks or a VPN, require authentication and logging, and never expose it directly to the public internet without a hardened gateway in front.
Where port 1723 is usually used
Most traffic on port 1723 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Remote workers establishing an encrypted tunnel to the office or cloud network.
- Site-to-site links between networks that must not expose internal services.
- Road-warrior clients roaming between Wi-Fi and mobile networks.
Probe the PPTP control port
PPTP is obsolete and insecure; this probe only confirms the TCP control listener is reachable.
nc -vz 127.0.0.1 1723Common problems with port 1723
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 1723. A timeout more often means a firewall drop, a wrong host or a service bound to a different interface.
Port already in use
Find the process holding the port with sudo ss -tlpn 'sport = :1723' or sudo lsof -i :1723. Stop that process or configure it to bind another port; killing it without identifying it can take down a production service.
Firewall rule did not survive a reboot
UFW and Windows Firewall keep rules across restarts. Raw iptables rules do not: save them with iptables-save or the netfilter-persistent package, and re-apply after upgrades that reset the ruleset.
The port is blocked but still reachable
A firewall rule filters inbound traffic; it does not close the listener. Confirm with the check command above and bind the service to 127.0.0.1 when only local clients need it.
Port 1723 at a glance
| Port number | 1723 |
|---|---|
| Service name | pptp |
| Transport protocol | TCP / UDP |
| Category | VPN and tunnelling |
| Range | Registered port (1024–10000) |
| Risk level | High |
| Registered assignee | [Ken_Crocker] |
| Reference | [RFC 2637] |
| Registry description | pptp |
| Source | IANA Service Name and Transport Protocol Port Number Registry |
Frequently asked questions
What is port 1723 used for?
Port 1723 (PPTP) uses TCP / UDP. pptp.
How do I check if port 1723 is open?
On Linux run `sudo ss -tlpn 'sport = :1723'` and `sudo ss -ulpn 'sport = :1723'`. On Windows run `Get-NetTCPConnection -LocalPort 1723 -State Listen -ErrorAction SilentlyContinue` and `Get-NetUDPEndpoint -LocalPort 1723 -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 1723; empty output usually means nothing is bound to it.
How do I block port 1723?
With UFW run `sudo ufw deny 1723/tcp` and `sudo ufw deny 1723/udp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 1723 -j DROP` and `sudo iptables -A INPUT -p udp --dport 1723 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 1723 safe to expose?
PPTP's MS-CHAPv2 authentication is cryptographically broken and the protocol is obsolete. Replace it with WireGuard, OpenVPN or IPsec. Nevertheless, treat this port as sensitive. Restrict it to trusted networks or a VPN, require authentication and logging, and never expose it directly to the public internet without a hardened gateway in front.
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Primary data: IANA Service Name and Transport Protocol Port Number Registry.
Last reviewed 2026-10-30 · Methodology · About · Privacy