UDP Port Setup |
UDP, or User Datagram Protocol, provides a method for application programs to send data to other programs over a network with only a minimum of protocol overhead. It is a much more efficient transport mechanism than TCP.
Although efficient, the use of UDP is not without risks. UDP offers only a minimal transport service and cannot guarantee complete datagram delivery. Because delivery and duplicate protection are not guaranteed, applications requiring the ordered, reliable delivery of data streams should use TCP.
The NetRS supports several streaming services on its UDP ports. You can create a UDP port from the I/O Port Summary page by selecting Create New UDP Port. You must enter a UDP Port Number. See the discussion below for guidance on picking those. You must also pick a UDP Timeout value, which is used by the keepalive system that maintains active UDP connections. You can also choose whether to use Port Authentication when clients attempt to make connections. Beyond that, select a Service type and enter the service-specific options.
The exact method for using a configured UDP port depends on the client platform, and the user's application program. At the lowest level, all that is usually needed is to send a small UDP data packet (whose contents are unimportant) to the NetRS IP address and the selected port. This will trigger the NetRS to begin streaming data back to the source of that packet. Data will continue to be sent to that location until the the UDP timeout elapses. The data flow can be maintained by the client by periodically sending keepalive packets at a rate faster than the UDP timeout. Multiple clients can establish UDP channels to the same UDP Port at the same time, and the same data will flow to all of the clients. Each of the clients must maintain their own channel using the keepalive mechanism.
It should be noted that once a UDP channel is triggered on the NetRS, data will be sent to the source of the triggering packet until the timeout occurs, regardless of whether the client is actually listening for the data. UDP is a connectionless protocol that does not actively monitor the other end of its channel. Nor does the UDP sender care whether its data packets manage to get through to the client.
The IANA, Internet Assigned Numbers Authority, manages the assignment of TCP and UDP ports from 0-1023.
Port Ids from 0-1023 should not be used. These ports are designated as well-known ports and have been assigned specific functions by the IANA. On most systems these ports can only be used by system processes or processes executed by priveledged users.
Port numbers 1024 - 49151 are called registered ports. They are used as logical connections to carry on long term conversations. On most systems these ports can be used by ordinary user processes. They are not controlled by the IANA, although the IANA registers their use as a convenience to the user community.
Port numbers 49152 - 65535 are called dynamic and/or private ports, and use of these ports should be avoided.
The IANA provides a list of accepted port number assignments that can be found at the following location: