Port 2401: CVS pserver
Port 2401 is CVS pserver, the password-authenticated server mode for the CVS version control system. CVS has largely been replaced by Subversion and Git, but the port is still occasionally seen on legacy infrastructure.
| Port number | 2401 |
|---|---|
| Service | CVS pserver |
| Protocol | TCP |
| Category | Version control |
| Default encryption | No |
How do I check whether port 2401 is open?
Port 2401 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 2401 | 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 2401 | 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 ':2401 ' | Lists the process bound to port 2401 on Linux. On macOS use lsof -nP -iTCP:2401 -sTCP:LISTEN, on Windows netstat -ano | findstr :2401 |
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 2401 used for?
Port 2401 is CVS pserver, the password-authenticated server mode for the CVS version control system. CVS has largely been replaced by Subversion and Git, but the port is still occasionally seen on legacy infrastructure.
Is port 2401 TCP or UDP?
Port 2401 (CVS pserver) uses TCP.
Is port 2401 secure?
Port 2401 is not encrypted by default. Where possible, use an encrypted alternative or tunnel it over TLS or a VPN.
Should I open port 2401 on my firewall?
Only if you specifically need CVS pserver. Expose it to the smallest set of trusted sources, and never open database or Windows-service ports to the whole internet.