BRev Port 1194 — OpenVPN
Port 1194/UDP is OpenVPN’s registered listener, and it is one of the few entries in this reference marked safe to expose — not as a concession but as the design. The whole point of a VPN endpoint is to be the single hardened door that lets everything else (RDP, SMB, databases, admin panels) stay closed. Authentication is certificate-based by default, the transport is TLS, and unauthenticated packets are dropped without a response.
UDP is the right default and the reason is TCP meltdown: run a TCP tunnel inside a TCP connection and the two retransmission timers fight each other, so a lossy link degrades far worse than it should. OpenVPN over UDP lets the inner TCP handle its own recovery. TCP mode exists for networks that block or mangle UDP, which is also why so many deployments move the listener to TCP 443 — it is indistinguishable from HTTPS to a naive filter and gets through hotel and corporate networks that drop everything else.
Being safe to expose is not being safe to neglect. tls-auth or tls-crypt adds an HMAC on the control channel so unauthenticated probes are dropped before any TLS work happens, which removes port-scan visibility and a class of denial-of-service. And the server still needs patching: this is code parsing hostile input from the internet by definition.
Port 1194 at a glance
| Field | Value | Detail |
|---|---|---|
| Port | 1194 | Registered |
| Service | OpenVPN | The classic OpenVPN listener. (UDP) |
| Category | Remote access | shells, desktops and VPNs |
| Exposure | Safe | Safe to expose |
Should port 1194 face the internet? Built to be the internet-facing door — that is the whole design.
Built to face the internet: authenticated, encrypted, and expected to take unsolicited connections. Still patch it.
What commonly goes wrong
You cannot tell whether the UDP port is open
You mostly cannot, and that is by design. A closed UDP port may return an ICMP port-unreachable, but firewalls usually suppress it; an open OpenVPN listener deliberately says nothing to an unauthenticated packet. So “no response” covers open, filtered and dropped alike. nmap -sU reports open|filtered honestly rather than guessing — the real test is whether a configured client completes a handshake.
The tunnel connects but no traffic flows
Connection and routing are separate problems. Check that the server pushes the routes you expect, that IP forwarding is enabled on the server, and that NAT (masquerade) covers the VPN subnet. On the client, a DNS leak or a missing route to the far subnet looks exactly like “the VPN is broken” while the tunnel itself is healthy.
Check port 1194 yourself
No browser can open a raw TCP socket, so no web page can honestly tell you whether this port is open on a remote host. These are the real commands, generated for port 1194 — swap example.com for the host you are actually testing.
Is port 1194 reachable on another host?
nc -vz example.com 1194"succeeded!" means the TCP handshake completed — the port is open. "Connection refused" is closed; a hang until timeout means filtered (a firewall dropped it silently).
nmap -Pn -p 1194 example.comThe only common tool that distinguishes open / closed / filtered. -Pn skips the ping sweep, so it still works against hosts that ignore ICMP.
Test-NetConnection example.com -Port 1194Read TcpTestSucceeded: True = open. It is built in — nothing to install.
telnet example.com 1194A blank screen or a banner means it connected. "Connection refused" means closed. Quit with Ctrl-] then `quit`.
curl -v --max-time 5 telnet://example.com:1194Handy when telnet is not installed: "Connected to …" proves the TCP handshake, without curl trying to speak HTTP.
What on this machine is holding port 1194?
sudo ss -tlnp | grep :1194Lists the listening socket and the PID/program holding it. Drop sudo and you get the socket but not the process name.
sudo lsof -i :1194The macOS answer to "address already in use". Kill it with `kill -9 <PID>` once you are sure what it is.
netstat -ano | findstr :1194The last column is the PID. Match it in Task Manager’s Details tab, or `taskkill /PID <pid> /F`.
No web page can tell you whether a port is open on a remote host
A browser cannot open a raw TCP socket — there is no API for it, by design. So a site that reports “port 3389 is OPEN on 203.0.113.10” is not checking from your browser; it is asking its own server to scan on your behalf. That works, but it means their server sees the host you asked about, scans from their address rather than yours, and answers a question about their network path, not yours.
We don't have a server here and won't pretend to. So this page does three honest things instead:
| Port | Proto | Service | What it is | Exposure | |
|---|---|---|---|---|---|
| 1194 | udp | OpenVPN | The classic OpenVPN listener.Built to be the internet-facing door — that is the whole design. | Safe |
http://host:port/ and times it. A connection that is established proves a socket is open; an instant refusal usually means nothing is listening; anything else is honestly reported as “can't tell”. Each attempt gives up after 2.5s.nc -vz example.com 443
nmap -Pn -p 443 example.com
telnet example.com 443
curl -v --max-time 5 telnet://example.com:443
This page cannot answer that, and neither can any other page — from your browser. Opening a TCP connection to an arbitrary host and port is not something JavaScript is allowed to do. Every “open port checker” that gives you a green tick is running the scan on their server. Which is fine, as long as you know what you are agreeing to: they learn which host and port you were worried about, and the answer they give you is about the route from their data centre — not from the internet as your users see it.
What to do instead
Run the check from outside your own network. Copy an nmap or nc line from the card above and run it from a machine that is not behind the same router — a phone on mobile data with a terminal app, a cheap VPS, a colleague's laptop. Running it from inside the LAN tests the LAN, not the internet, and will happily say “open” while the world sees nothing.
Then check the thing that is actually blocking it, in this order: the service is bound to0.0.0.0 and not 127.0.0.1 · the host firewall (ufw, firewalld, Windows Defender Firewall) · the cloud security group or the router's port-forward rule · and finally your ISP, which commonly blocks 25, 80 and 445 on residential lines whatever you configure.
What a browser genuinely can verify
One thing: that an HTTPS service answers. If what you actually want to know is “is my site up and how fast is it”, the latency test measures real round trips to a CORS-open URL. If the name doesn't resolve, or resolves somewhere unexpected, that is a DNS problem, not a port problem — and it is the more common cause of “my port is closed” than an actual firewall.
An IP address finds the machine; a port picks which program on it gets the traffic. TCP sets up a connection first — a handshake, ordered delivery, retransmission — which is why the web, email and SSH use it. UDP just sends the packet with no handshake and no guarantee it arrives, which is why DNS, video calls and games use it: late data is worse than lost data.
That difference is why a UDP port is so much harder to test. TCP either completes a handshake or it doesn't, so a tool can tell you. A UDP service that has nothing to say to an unexpected packet stays silent — and silence looks identical to a firewall dropping it.
The three ranges
0–1023Assigned by IANA to core services. On Unix, binding one needs root (or CAP_NET_BIND_SERVICE).1024–49151Registered by vendors for their applications. Any user can bind these — which is why every dev server lives here.49152–65535Never assigned. The OS hands these out as the SOURCE port of your outgoing connections. (Linux actually uses 32768–60999 by default.)Closed is not the same as filtered
Closed means the host answered: the packet arrived, nothing is listening, and you got an immediate refusal (a TCP RST). Filtered means nothing answered at all — a firewall dropped your packet in silence, so you wait for a timeout and learn nothing. The difference matters: closed proves the host is reachable and the port is free; filtered tells you only that something between you and it is discarding traffic.nmap reports the two separately. A browser cannot distinguish them, which is why this page reports a timeout as “can't tell” rather than guessing.
The one habit worth keeping
Bind services to 127.0.0.1 instead of 0.0.0.0 unless something outside the machine genuinely needs them, and reach them over SSH or a VPN. Every database on the never-expose list above ships with that advice, and the leaks all begin the same way: a default bind address, a cloud instance with a public IP, and a scanner that found it within the hour.
The blocked-port list this page uses is the WHATWG Fetch Standard's “bad port” table — the ports every browser refuses to connect to (Chrome calls it ERR_UNSAFE_PORT). Local probing is additionally gated by Chrome's Local Network Access permission, which replaced Private Network Access and ships in Chrome 142.
FAQ
Is it safe to expose port 1194 to the internet?
Yes — a VPN endpoint has to be reachable to be useful, and OpenVPN is built for it: certificate authentication, TLS transport, and silence toward unauthenticated packets. Add tls-crypt so probes are dropped before TLS, and keep the server patched.
Should I use UDP or TCP for OpenVPN?
UDP unless something forces otherwise. Tunnelling TCP inside TCP stacks two retransmission timers on the same loss and performs badly. TCP mode — usually on 443 — is the fallback for restrictive networks.
How does this compare to WireGuard on 51820?
WireGuard is smaller, faster and simpler to configure, and it is also UDP-only and equally silent to unauthenticated packets. OpenVPN’s advantages are maturity, TCP fallback and far richer authentication integration. Both are legitimate internet-facing endpoints; PPTP on 1723 is not.