Port allocation

Many web application modules need a TCP or UDP port to run a backend exposed by Traefik. Such modules can set the org.nethserver.tcp-ports-demand and org.nethserver.tcp-ports-demand which takes an integer number as value. Example:


The randomly-allocated TCP port number will be available inside the TCP_PORT environment variable and it will be available to all step scripts and inside systemd units. The available environment variables will be:

  • TCP_PORT, UDP_PORT: it is always present and it contains always the first port, i.e. 20001
  • TCP_PORTS_RANGE, UDP_PORTS_RANGE: only if value is greater than 1, it contains the list of ports in range format, i.e 20001-20002
  • TCP_PORTS, UDP_PORTS: only if value is greater than 1 and less or equal than 8, it contains a comma separated list of ports like, i.e. 20001,20002,20003

Currently last allocated port is saved inside Redis at node/<node_id>/tcp_ports_sequence, node/<node_id>/udp_ports_sequence.