Add configurable start port for Jupyter kernels and servers

[Copilot]

Overview

This PR adds a new configuration setting that allows users to configure the starting port number used when launching Jupyter kernels and servers. This addresses the need for users in corporate environments, restricted networks, or those running multiple VS Code instances to control which ports the extension uses.

Closes #10765

Problem

Previously, the Jupyter extension hardcoded the starting port to 9000 for both:

• Raw kernel launches (which require 5 ZeroMQ ports: shell, iopub, stdin, control, and heartbeat)
• Local Jupyter server launches

This caused issues for users who:

• Work in corporate environments with restricted port ranges
• Need to configure firewalls to allow specific ports
• Run multiple VS Code instances simultaneously and encounter port conflicts
• Have other applications already using ports in the 9000 range

Solution

Added a new VS Code setting: jupyter.kernels.portRange.startPort

Configuration:

• Type: number
• Default: 9000 (maintains backward compatibility)
• Range: 1024-65535 (enforced by VS Code validation)
• Scope: machine (applies system-wide, can be overridden per workspace)

Usage:

{
    "jupyter.kernels.portRange.startPort": 10000
}

Implementation Details

For Raw Kernels

Modified KernelLauncher to dynamically read the configured start port and use it when allocating the 5 required ZeroMQ ports. The implementation:

• Detects configuration changes automatically
• Re-initializes port allocation when the configured port changes
• Maintains backward compatibility with the default behavior

For Jupyter Servers

Modified JupyterServerStarter to pass --port=<configured_port> to the Jupyter server command line when a non-default port is configured. When using the default port (9000), Jupyter uses its own port selection mechanism to maintain backward compatibility.

Port Allocation Behavior

• If the configured port is available, it will be used
• If the configured port is in use, the extension automatically finds the next available port
• Multiple kernels each get their own set of ports starting from the configured range
• Port conflicts are handled gracefully with automatic fallback

Testing

Added comprehensive unit tests:

• ✅ Verified custom start port configuration works correctly
• ✅ All existing tests continue to pass (no regressions)
• ✅ Configuration service tests: 7/7 passing
• ✅ Kernel launcher tests: 3/3 passing

Backward Compatibility

This change is fully backward compatible:

• Default behavior unchanged (still uses port 9000)
• No breaking changes to existing functionality
• Opt-in feature (users must explicitly configure to change behavior)
• Graceful fallbacks if configured port is unavailable

Code Quality

• ✅ No compilation errors
• ✅ No linting warnings
• ✅ Code formatting compliant
• ✅ Comprehensive test coverage

Use Cases

Corporate Environment:

{
    "jupyter.kernels.portRange.startPort": 50000  // Use allowed port range
}

Multiple VS Code Instances:

// Instance 1
{
    "jupyter.kernels.portRange.startPort": 10000
}

// Instance 2
{
    "jupyter.kernels.portRange.startPort": 20000
}

Firewall Configuration:

{
    "jupyter.kernels.portRange.startPort": 12000  // Specific allowed range
}

Files Changed

• package.json - Added configuration setting with validation
• package.nls.json - Added localized description
• src/platform/common/types.ts - Added property to IJupyterSettings interface
• src/platform/common/configSettings.ts - Added property initialization
• src/kernels/raw/launcher/kernelLauncher.node.ts - Updated port allocation logic
• src/kernels/jupyter/launcher/jupyterServerStarter.node.ts - Added port argument generation
• src/kernels/raw/launcher/kernelLauncher.unit.test.ts - Added test coverage

Security Considerations

• Minimum port of 1024 prevents use of privileged ports (0-1023)
• Port validation ensures only valid port numbers can be configured
• No new network endpoints or attack surface added
• Existing port forwarding prevention continues to work

Original prompt

---

This section details on the original issue you should resolve

<issue_title>still needing a way to configure the start port as described in locked issues</issue_title>
<issue_description>

#10765

• i am no expert in vscode extension development

• it would be great to have this port as a setting

• other instructions for changing ports via flags did not work for me (i guess these are outdated)

  • https://stackoverflow.com/questions/57382404/how-to-change-port-used-by-anaconda-jupyter-notebooks-in-visual-studio-code

• i was not able to find the code of the extension (my goal would be to just replace the hardcoded port for testing purposes)
  </issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes #16810

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