A port is a communication resource identified by a transport protocol (TCP or UDP) and a number between 1 and 65,535. Ports are associated to connections. A device connects to a destination through a particular port.
In reality, two ports are needed to establish a connection: one port in the device and another port in the destination. However, only the port of the destination is important, because it is the one that usually determines the network service. Server applications on destinations listen to connection requests on well-known ports that are associated to standardized network services. For example, the SMTP mail service uses TCP port 25 for incoming requests. For this reason, Nexthink stores information about the destination ports only.
The type of the port is determined by the transport protocol. There are two types of ports:
In addition to TCP and UDP ports, there are two other special types of ports in Nexthink which are associated to connections identified as port scans:
- TCP port scan
- UDP port scan
These special types of ports are not linked to just one but to multiple port numbers. To reflect this particularity, Nexthink assigns to these ports the port number 0. which is actually a reserved port number that is never used.