Selecting UDP ports

Last published : Sep 11, 2026
When you select a UDP port, select an available 16-bit integer from the range that follows:
  • Use available ports in the private range 49152 to 65535
  • Do not use the following ports:
    • Ports from the range of well-known ports, 0 to 1023
    • Ports from the range of registered ports, 1024 to 49151
To check which ports are defined as defaults for a node, examine the file /etc/services. You should also use the netstat command to list the UDP ports currently in use. For example:
\# netstat -a | more
Active Internet connections (including servers)
Proto Recv-Q Send-Q  Local Address   Foreign Address   (state)
tcp        0      0  *.32778*.*               LISTEN
tcp        0      0  *.32781*.*               LISTEN
udp4       0      0  *.daytime*.*udp4       0      0*.time          *.*udp4       0      0*.sunrpc        *.*udp        0      0*.snmp          *.*
Look in the UDP section of the output; the UDP ports that are listed under Local Address are already in use. If a port is listed in the /etc/services file, its associated name is displayed rather than the port number in the output.