Port 4990

busycal · TCP/UDP

RangeRegistered port (1024–49151)
ProtocolTCP/UDP
Servicebusycal
Registered2008-01-07

Frequently asked questions

What is port 4990 used for?

Port 4990 is registered with the IANA for busycal (TCP/UDP). Description: BusySync Calendar Synch. Protocol.

Is port 4990 a well-known port?

No. Port 4990 is in the range 1024–49151 (registered or user ports). Ordinary programs may open it without root privileges.

How do I check whether port 4990 is open?

Locally on Linux with ss -tulpn | grep ':4990\b', on Windows with netstat -ano | findstr :4990. To test a remote host use Test-NetConnection <host> -Port 4990 in PowerShell or nc -zv <host> 4990 on Linux/macOS.

How do I open port 4990 in the firewall?

Ubuntu/Debian (ufw): sudo ufw allow 4990/tcp. Fedora/RHEL (firewalld): sudo firewall-cmd --add-port=4990/tcp --permanent, then firewall-cmd --reload. Windows (PowerShell as administrator): New-NetFirewallRule -DisplayName "Port 4990" -Direction Inbound -Protocol TCP -LocalPort 4990 -Action Allow.

IANA registry entries

ProtocolServiceDescription (IANA)
TCPbusycalBusySync Calendar Synch. Protocol
UDPbusycalBusySync Calendar Synch. Protocol

Nearby entries