Port 873 is a port that is utilized by the User Datagram Protocol or can also be referred to as a Universal Datagram Protocol or in short, UDP. This protocol bears the protocol name rsync,rsync and a port description of rsync.'rsync'. This UDP port 873 is not a virus or a Trojan and it is not easily susceptible to the Trojans and the viruses. The UDP Port 873 may use a protocol that is defined for communication and it all depends on the application. Protocols are set of rules, which are formalized rules that explain how data is to be communicated across a network.
The rsync application essentially uses the port 873. This application can only be found on computers that are running on the UNIX OS. Rsync is utilized in the synchronization of folders and files in computers, even when the machines are not connected or physically close to each other. This information is transferred through the Local Access Network or the LAN or the Internet. The application associated with the port runs a background process and also listens to the port 873 on the TCP protocol. This information that is passing through this port 873 flows to and fro the computer.