Debugging

Debugging & Remote Attach (VS Code) — Deep Guide

This page shows local and remote debugging setups for Python, Node.js, Java, PHP, and .NET using VS Code, including remote attach and container/VM workflows.

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1) Python (debugpy)

Local attach

1. pip install debugpy

2. Inject into the target app:

import debugpy
print('[*] starting debug server on 0.0.0.0:5678')
debugpy.listen(('0.0.0.0', 5678))
debugpy.wait_for_client()  # optional if you want to break immediately

1. VS Code → Run & Debug → launch.json:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Attach (debugpy)",
      "type": "python",
      "request": "attach",
      "host": "127.0.0.1",
      "port": 5678
    }
  ]
}

Remote attach (SSH/VM/container)

• Open folder via Remote‑SSH / Dev Containers.

• Expose 5678 (VM security groups / container port mapping).

• Same launch.json but host is remote IP.

Breakpoints & Watch

• Set breakpoints in source files; use Call Stack and Variables panes.

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2) Node.js (Inspector)

Start with inspector

node --inspect=0.0.0.0:9229 app.js
# or attach to running process: node --inspect-port=9229 --pid <PID>

VS Code attach

{
  "version": "0.2.0",
  "configurations": [
    {
      "type": "node",
      "request": "attach",
      "name": "Attach Node",
      "address": "127.0.0.1",
      "port": 9229,
      "restart": true,
      "protocol": "inspector"
    }
  ]
}

Debugging WebSockets & front‑end

• Use Chrome DevTools (Sources, Network → WS frames); set breakpoints in bundled JS via source maps.

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3) Java (JDWP)

Enable remote debug flags

Add to JVM args:

-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005

VS Code (Extension Pack for Java)

{
  "version": "0.2.0",
  "configurations": [
    {
      "type": "java",
      "name": "Attach Java",
      "request": "attach",
      "hostName": "127.0.0.1",
      "port": 5005
    }
  ]
}

Tips

• If classpaths differ, attach to correct process; use break on thrown exceptions.

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4) PHP (Xdebug)

Install & configure

1. pecl install xdebug or enable distro pkg.

2. php.ini:

xdebug.mode=debug
xdebug.start_with_request=yes
xdebug.client_host=127.0.0.1
xdebug.client_port=9003

1. Restart web server.

VS Code

Install PHP Debug extension; launch.json:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Listen for Xdebug",
      "type": "php",
      "request": "launch",
      "port": 9003
    }
  ]
}

Remote

• Set xdebug.client_host to your workstation IP; open port 9003; map paths with pathMappings if containerized.

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5) .NET (vsdbg)

Remote debugging Linux

1. Download vsdbg:

curl -sSL https://aka.ms/getvsdbgsh | bash /dev/stdin -v latest -l ~/vsdbg

1. Start your app with symbols (dotnet run).

2. VS Code launch.json:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Attach .NET",
      "type": "coreclr",
      "request": "attach",
      "processId": "${command:pickProcess}",
      "pipeTransport": {
        "pipeProgram": "ssh",
        "pipeArgs": ["user@remote"],
        "debuggerPath": "~/vsdbg/vsdbg"
      }
    }
  ]
}

Windows

• Use processId attach; ensure Just My Code disabled for mixed sources.

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6) Remote Attach JavaScript file (front‑end)

Live editing & breakpoints

• Open site in Chrome → Sources → locate bundle → set breakpoints.

• For remote files, enable workspace mapping in DevTools → use local copies.

VS Code Edge/Chrome Debugging

{
  "type": "pwa-chrome",
  "request": "launch",
  "name": "Launch App",
  "url": "http://localhost:8080",
  "sourceMaps": true
}

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7) Containers & SSH

• Use Dev Containers to mount repo; include debug servers in Dockerfile.

• Remote‑SSH: ~/.ssh/config host entries; open debug ports in security groups.

8) Breakpoint Strategy

• Start at controllers; add conditional breakpoints on user == 'admin' branches.

• Watch values: session objects, cookies, JWT claims.

Tip: In exam VMs, avoid noisy logs; use minimal debug prints and remove them after analysis.