[JENKINS-16056] Numbered ports don't check whether the port is actually in use

If you create a numbered TCP port (e.g. "9876", as opposed to a named port), then the plugin doesn't appear to actually check whether this port is free on the slave.

i.e. It only checks that no other builds are using the port.

Preferably, as with named ports, the actual availability of the port on the slave should be checked.

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Originally reported by orrc, imported from: Numbered ports don't check whether the port is actually in use

• assignee: ramapulavarthi
  
• status: Open
  
• priority: Minor
  
• component(s): port-allocator-plugin
  
• resolution: Unresolved
  
• votes: 0
  
• watchers: 1
  
• imported: 20251216-225446
  

Raw content of original issue

If you create a numbered TCP port (e.g. "9876", as opposed to a named port), then the plugin doesn't appear to actually check whether this port is free on the slave.


i.e. It only checks that no other builds are using the port.


Preferably, as with named ports, the actual availability of the port on the slave should be checked.

Start in the port-allocator-plugin code path for numbered TCP port allocation and compare it with the existing named-port availability check. Reproduce the issue by occupying a numbered port on a slave, then verify that allocation rejects the occupied port while retaining build-level reservation behavior.

Written by the indexing model from the issue text.