CAMEL-22525: Fix flaky AS2 tests by eliminating port allocation race condition

[gnodet]

CAMEL-22525

Summary

• Add getLocalPort() to AS2ServerConnection and AS2AsyncMDNServerConnection to expose the actual bound port
• Eliminate the TOCTOU race condition in AS2 tests by binding to port 0 (OS assigns a free port atomically) instead of pre-allocating a port with AvailablePortFinder which probes then closes a socket, leaving a window for another process to steal the port
• Rename non-final static fields to camelCase (TARGET_PORT → targetPort, RECIPIENT_DELIVERY_ADDRESS → recipientDeliveryAddress)

Root Cause

AvailablePortFinder.find() opens a ServerSocket on port 0, records the assigned port, then closes the socket. When AS2ServerConnection later tries to bind to that port, another process may have already claimed it — a classic TOCTOU (time-of-check-to-time-of-use) race condition. This was particularly flaky on s390x CI where multiple processes compete for ports.

The prior fix (SO_REUSEADDR in #22095) helped with TIME_WAIT state but didn't eliminate the fundamental race.

Fix

Instead of pre-allocating a port number, tests now:

1. Create AS2ServerConnection with port 0 — the OS assigns a free port atomically during bind()
2. Read the actual port back via the new getLocalPort() method
3. Use that port to configure the client

This completely eliminates the race condition since port assignment and binding happen in a single atomic operation.

Test plan

• All 94 camel-as2-api tests pass
• All 12 camel-as2-component tests pass (1 skipped: manual Mendelson test)
• Code formatted with mvn formatter:format impsort:sort

[github-actions]

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[github-actions]

🧪 CI tested the following changed modules:

• components/camel-as2/camel-as2-api
• components/camel-as2/camel-as2-component

All tested modules (9 modules)

• Camel :: AS2 :: API
• Camel :: AS2 :: Component
• Camel :: JBang :: MCP
• Camel :: JBang :: Plugin :: Route Parser
• Camel :: JBang :: Plugin :: TUI
• Camel :: JBang :: Plugin :: Validate
• Camel :: Launcher :: Container
• Camel :: YAML DSL :: Validator
• Camel :: YAML DSL :: Validator Maven Plugin

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[apupier]

given that it is no more a final attribute:

"Rename this field "RECIPIENT_DELIVERY_ADDRESS" to match the regular expression '^[a-z][a-zA-Z0-9]*$'."

[gnodet]

Claude Code on behalf of Guillaume Nodet

Good catch — renamed RECIPIENT_DELIVERY_ADDRESS to recipientDeliveryAddress since it's no longer a constant. Fixed in 7413a4a.

[apupier]

given that it is no more a final attribute:

"Rename this field "RECIPIENT_DELIVERY_ADDRESS" to match the regular expression '^[a-z][a-zA-Z0-9]*$'."

[gnodet]

Claude Code on behalf of Guillaume Nodet

Good catch — renamed TARGET_PORT to targetPort since it's no longer a constant. Fixed in 7413a4a.

[apupier]

shouldn't we return 0 to let the system pick an ephemeral port?

[gnodet]

Claude Code on behalf of Guillaume Nodet

Returning -1 is intentional — it follows the ServerSocket.getLocalPort() convention where -1 means "not bound / closed". Returning 0 would be misleading since 0 means "pick an ephemeral port" in socket APIs, which could cause silent bugs if the value is accidentally passed to another new ServerSocket(0) or bind() call. The -1 sentinel makes the error explicit.