Whenever an AppServer Internet Adapter (AIA) or WebSpeed Messenger instance communicates with a NameServer, the instance is assigned a UDP port. The NameServer uses this port to send a response message to the instance. By default this port is dynamically assigned by the operating system within the UDP port range of 1024 to 65535.
If there is a firewall between the instance and the NameServer, the default setting requires that all UDP ports in that range must be open from the network where the NameServer exists to the network where the AIA or Messenger instance exists. Otherwise, communication between the instance and the NameServer cannot occur.
However, the only port that must be open in the firewall is the controlling NameServer port for UDP traffic going from the network containing the AIA or Messenger instance to the network containing the NameServer. To increase security, you can limit the range of ports from which an AIA or Messenger instance can be assigned an UDP port. The NameServer Client Port Minimum (minNSClientPort) and the NameServer Client Port Maximum (maxNSClientPort) properties can be used to reduce the number of UDP ports that you must open in the firewall. When you set these properties, OpenEdge chooses the first port in that range that is not currently used by some other application for UDP broadcast communications. If no port in this range is available, the default behavior is to retry the ports for a period of time.
