In network terms, a port is a communication endpoint used by the transport protocol to facilitate the stream of information. Every single piece of data has a destination port associated with it, and this port is associated with a number to enable the server to sort traffic and deliver the data to the correct recipient.
Port numbers range from 0 to 65535. For VoIP traffic, the standard port is 5060, which is used for both TCP and UDP connections. Consider it the gateway for VoIP functions such as media streaming and video conferencing. Often, port 5004 UDP is preferred when transmitting packets of data within a computer network.
VoIP phone and communications providers use a variety of ports based on their specific product designs and requirements. They may also have a supplementary list of UDP ports for when they need to upgrade their products.
Apart from network ports, you may also need hardware ports in order to use complementary VoIP accessories. These can include headsets for devices not designed to be used like regular telephones and USB ports for USB phones.