fix: restore ZMQ ipc:// Unix domain socket support

[JohnnyLawDGB]

Summary

• Restores ZMQ Unix domain socket (ipc://) support that broke in v8.26 during the Bitcoin Core v26.2 merge
• Splits the port validation loop so ZMQ options skip validation for ipc:// addresses while TCP-only options (-rpcbind, -proxy, etc.) retain strict validation
• Backward compatible with DigiByte v8.22.2 configurations and existing documentation (doc/zmq.md:88)

Background

Port validation added in the v26.2 merge rejects ipc:// addresses because SplitHostPort() expects host:port format. Unix domain sockets use filesystem paths (ipc:///tmp/dgb.hashblock), not ports. This causes nodes configured with zmqpubhashblock=ipc:///tmp/dgb.hashblock to crash on startup with "Invalid port specified".

Bitcoin Core fixed this in v28.0 (PRs #27375, #27679) using a unix: prefix with internal ipc:// conversion. This PR takes a simpler approach — directly allowing ipc:// — since DigiByte v8.22.2 already used ipc:// and libzmq natively supports it.

Targeting feature/digidollar-v1 for testnet validation, intended for inclusion in v9.26 mainnet release.

Fixes #340

Test plan

• Verify zmqpubhashblock=ipc:///tmp/dgb.hashblock no longer crashes on startup
• Verify zmqpubhashblock=tcp://127.0.0.1:212024 still works (TCP validation intact)
• Verify invalid TCP addresses (e.g. zmqpubhashblock=tcp://badhost) are still rejected
• Verify non-ZMQ options (-rpcbind, -proxy) still require valid ports

🤖 Generated with Claude Code

[DigiSwarm]

Hey @JohnnyLawDGB — did a full audit of this PR and I appreciate the work here. The ZMQ ipc:// fix is correct and well-executed. The root cause is right: the v26.2 port validation merge broke Unix domain socket support by folding ZMQ options into the same SplitHostPort() loop as -rpcbind. Splitting the loop and adding the ipc:// bypass is the right approach — clean, minimal, and backward compatible with v8.22.2 configs.

Note: the macOS CI failure appears to be a pre-existing flaky test issue unrelated to your change (Ubuntu passes clean). The actual diff is only the src/init.cpp change — the rest of the Files changed view was divergence from our branch moving forward since you forked.

Merging — thanks for tracking down and fixing this one. 🙏

[8eS3rz4sDu8oUx4q39hhv8o2k2e72dkb]

Hello everyone! Thank you for taking the time to deep dive into this issue. I hope it has been solved by now.

Does that mean I can test it on a testnet using version DigiByte v9.26.0-rc24 ?