Port 513: rlogin
Port 513 is rlogin, an old remote-login protocol from the Berkeley r-commands suite that offers no encryption. SSH on port 22 replaced it because rlogin trusted the client's claimed identity far too easily.
| Port number | 513 |
|---|---|
| Service | Remote login |
| Protocol | TCP |
| Category | Remote access |
| Default encryption | No |
How do I check whether port 513 is open?
Port 513 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 513 | 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 513 | 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 ':513 ' | Lists the process bound to port 513 on Linux. On macOS use lsof -nP -iTCP:513 -sTCP:LISTEN, on Windows netstat -ano | findstr :513 |
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 513 used for?
Port 513 is rlogin, an old remote-login protocol from the Berkeley r-commands suite that offers no encryption. SSH on port 22 replaced it because rlogin trusted the client's claimed identity far too easily.
Is port 513 TCP or UDP?
Port 513 (rlogin) uses TCP.
Is port 513 secure?
Port 513 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 513 on my firewall?
Only if you specifically need rlogin. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.