Where a PBS or TORQUE batch server contacts its scheduler.
pbs_server looks for the scheduler on the loopback address at port 15004 unless started with -S; pbs_sched binds it. It completes the 15001-15005 block that TORQUE and PBS use (server, MOM, MOM resource manager, scheduler, trqauthd). Seeing it open means an HPC head node. The port is unassigned at IANA — the number comes from the PBS source, not a registration.
Do not expose
Normally a loopback-only conversation between two daemons on the head node; a scheduler port answering from outside the cluster is a misconfiguration.
$ sudo lsof -nP -iTCP:15004 -sTCP:LISTENSeen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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Corrections or a missing port? Reply @rimrocksystems.