Which of the following is the valid port for remote desktop protocol?

Port 110 is assigned to POP3 (Post Office Protocol version 3), used for retrieving email from a mail server, not remote desktop access.

Port 443 is assigned to HTTPS (HTTP over TLS/SSL), used for secure web traffic, not remote desktop sessions.

RDP operates on TCP port 3389 by default, allowing a client to establish a remote graphical session to a Windows host. This port must be open on the firewall and the Remote Desktop service must be enabled on the target machine for connections to succeed.

Port 8080 is a common alternate port for HTTP web traffic or proxy services, not the RDP protocol.