Fix/python tcpip socket read timeout

[jmthomas]

What changed

Python's select.select returns ([], [], []) on timeout, which fell into the retry branch and looped forever, so read_timeout never bounded an idle-but-open socket. Give the timeout its own branch matching the Ruby stream and write(), and treat only closed-socket errors from select as EOF.

Why it changed

closes #3751

Testing strategy

Unit tests

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.30%. Comparing base (b5ee05d) to head (441afd0).
⚠️ Report is 44 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3823      +/-   ##
==========================================
+ Coverage   79.27%   79.30%   +0.03%     
==========================================
  Files         895      896       +1     
  Lines       67271    67393     +122     
  Branches     2641     2659      +18     
==========================================
+ Hits        53327    53448     +121     
- Misses      13273    13275       +2     
+ Partials      671      670       -1     

Flag	Coverage Δ
frontend	66.48% <ø> (+0.27%)	⬆️
python	79.38% <ø> (+0.02%)	⬆️
ruby-api	82.36% <ø> (-0.14%)	⬇️
ruby-backend	84.58% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[Copilot]

🟡 Changes recommended

The new select() ValueError handling is overly broad (can mask real configuration/programming errors) and the new/updated tests still rely on fixed ports, which can make CI flaky.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Fixes Python TcpipSocketStream.read() so read_timeout correctly bounds an idle-but-open socket by distinguishing select() timeouts from “retry” readiness, aligning behavior with the Ruby implementation and the existing interface-level timeout handling.

Changes:

• Fix TcpipSocketStream.read() to raise TimeoutError("Read Timeout") when select.select times out, instead of looping forever.
• Treat only closed-socket failures from select as EOF while re-raising unexpected select failures.
• Add targeted unit tests covering timeout, retry-on-readable, disconnect signaling, and select error handling.

File summaries

File	Description
openc3/python/openc3/streams/tcpip_socket_stream.py	Adds explicit timeout handling and refines select() error handling in read() to prevent infinite retry loops.
openc3/python/test/streams/test_tcpip_socket_stream.py	Adds regression/unit tests for read timeout behavior and related select/EOF cases; introduces a reusable TCP server helper.
openc3/python/openc3/interfaces/tcpip_server_interface.py	Uses setblocking(False) for clarity/consistency.

Review details

Suppressed comments (2)

openc3/python/test/streams/test_tcpip_socket_stream.py:161

• This new test binds to a fixed TCP port (20004). Fixed ports can make the suite flaky under parallel runs or if the port is in use. Prefer binding to port 0 and connecting to server.server_address[1].

        server = ReusableTCPServer(("localhost", 20004), MyTCPHandler)
        threading.Thread(target=server.handle_request).start()
        rs = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
        rs.connect(("localhost", 20004))

openc3/python/test/streams/test_tcpip_socket_stream.py:183

• This test binds to a fixed TCP port (20002). To avoid intermittent failures due to port collisions, bind to an ephemeral port (0) and use server.server_address[1] for the client connection.

        server = ReusableTCPServer(("localhost", 20002), MyTCPHandler)
        threading.Thread(target=server.handle_request).start()
        rs = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
        rs.connect(("localhost", 20002))

• Files reviewed: 3/3 changed files
• Comments generated: 2
• Review effort level: Lite

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[ryanmelt]

Implement Copilot suggestions

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud