Port 3389: RDP
Port 3389 is RDP, Windows Remote Desktop. It is one of the most-attacked ports on the internet, so put it behind a VPN or gateway rather than exposing it directly.
| Port number | 3389 |
|---|---|
| Service | Remote Desktop Protocol |
| Protocol | TCP |
| Category | Remote access |
| Default encryption | No |
How do I check whether port 3389 is open?
Port 3389 carries TCP, so a connection either completes its handshake or it does not, which makes the check definitive.
| Question | Command | What to know |
|---|---|---|
| Is it open on a remote host? | nc -vz example.com 3389 | A TCP handshake either completes or it does not, so netcat gives a definitive answer in one line. |
| Same check on Windows | Test-NetConnection example.com -Port 3389 | Built into PowerShell. TcpTestSucceeded in the output is the answer; telnet is not installed by default on modern Windows. |
| What is listening locally? | ss -tlnp | grep ':3389 ' | Lists the process bound to port 3389 on Linux. On macOS use lsof -nP -iTCP:3389 -sTCP:LISTEN, on Windows netstat -ano | findstr :3389 |
Replace example.com with the host you are testing. A blocked port and a port with nothing listening on it look identical from the outside, so if a service should be running, check locally before blaming the firewall.
Frequently asked questions
What is port 3389 used for?
Port 3389 is RDP, Windows Remote Desktop. It is one of the most-attacked ports on the internet, so put it behind a VPN or gateway rather than exposing it directly.
Is port 3389 TCP or UDP?
Port 3389 (RDP) uses TCP.
Is port 3389 secure?
Port 3389 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 3389 on my firewall?
Only if you specifically need RDP. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.