Unable to connect to MCP Server, tested using multiple AI Agent: VSCode, OpenCode, Claude Code

[Entropt]

My setup:

• Windows 11
• Python 3.11.9 (https://www.python.org/downloads/windows/)
• IDA Pro 9.1
• Tried both Python and virtual environment.

Tried on multiple AI Agent, even Claude Desktop, the error code seems to be the same so I will list out only the error on Claude Desktop:

2026-02-03T02:10:04.104Z [ida-pro-mcp] [info] Using MCP server command: C:\Users\tuandm4\mcp_env\Scripts\python.exe with args and path: {
  metadata: {
    args: [
      'C:\\Users\\tuandm4\\mcp_env\\Lib\\site-packages\\ida_pro_mcp\\server.py',
      '--ida-rpc',
      'http://127.0.0.1:13337',
      [length]: 3
    ],
    paths: [
      'C:\\Program Files\\Python311',
      'C:\\Python311',
      'C:\\Program Files\\Git\\cmd',
      'C:\\Program Files\\Git\\mingw64\\bin',
      'C:\\Python311\\Scripts\\',
      'C:\\Python311\\',
      'C:\\Program Files\\Common Files\\Oracle\\Java\\javapath',
      'C:\\Windows\\system32',
      'C:\\Windows',
      'C:\\Windows\\System32\\Wbem',
      'C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\',
      'C:\\Windows\\System32\\OpenSSH\\',
      'C:\\Program Files\\NVIDIA Corporation\\NVIDIA App\\NvDLISR',
      'C:\\Program Files (x86)\\NVIDIA Corporation\\PhysX\\Common',
      'C:\\Program Files\\dotnet\\',
      'C:\\Program Files\\Go\\bin',
      'C:\\Program Files\\Docker\\Docker\\resources\\bin',
      'C:\\Users\\tuandm4\\AppData\\Local\\nvm',
      'C:\\nvm4w\\nodejs',
      'C:\\Users\\tuandm4\\AppData\\Local\\Microsoft\\WindowsApps',
      'C:\\Users\\tuandm4\\AppData\\Local\\Programs\\Microsoft VS Code\\bin',
      'C:\\Users\\tuandm4\\go\\bin',
      'C:\\Users\\tuandm4\\AppData\\Local\\Packages\\PythonSoftwareFoundation.Python.3.13_qbz5n2kfra8p0\\LocalCache\\local-packages\\Python313\\Scripts',
      'C:\\Users\\tuandm4\\platform-tools',
      'C:\\Users\\tuandm4\\.local\\bin',
      'C:\\Users\\tuandm4\\AppData\\Roaming\\Hex-Rays\\IDA Pro\\plugins',
      '',
      [length]: 27
    ]
  }
} %o
2026-02-03T02:10:04.401Z [ida-pro-mcp] [info] Server started and connected successfully { metadata: undefined }
2026-02-03T02:10:04.426Z [ida-pro-mcp] [info] Message from client: {"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"claude-ai","version":"0.1.0"}},"jsonrpc":"2.0","id":0} { metadata: undefined }
2026-02-03T02:10:04.764Z [ida-pro-mcp] [info] Message from server: {"jsonrpc":"2.0","id":0,"result":{"protocolVersion":"2025-06-18","capabilities":{"tools":{},"resources":{"subscribe":false,"listChanged":false},"prompts":{}},"serverInfo":{"name":"ida-pro-mcp","version":"1.0.0"}}} { metadata: undefined }
2026-02-03T02:10:04.912Z [ida-pro-mcp] [info] Message from client: {"method":"notifications/initialized","jsonrpc":"2.0"} { metadata: undefined }
2026-02-03T02:10:04.913Z [ida-pro-mcp] [info] Message from client: {"method":"tools/list","params":{},"jsonrpc":"2.0","id":1} { metadata: undefined }
2026-02-03T02:10:04.914Z [ida-pro-mcp] [info] Message from client: {"method":"prompts/list","params":{},"jsonrpc":"2.0","id":2} { metadata: undefined }
2026-02-03T02:10:04.914Z [ida-pro-mcp] [info] Message from client: {"method":"resources/list","params":{},"jsonrpc":"2.0","id":3} { metadata: undefined }
2026-02-03T02:10:04.933Z [ida-pro-mcp] [info] Message from server: {"jsonrpc":"2.0","id":1,"error":{"code":-32000,"message":"Failed to connect to IDA Pro! Did you run Edit -> Plugins -> MCP (Ctrl+Alt+M) to start the server?\nTraceback (most recent call last):\n  File \"C:\\Users\\tuandm4\\mcp_env\\Lib\\site-packages\\ida_pro_mcp\\server.py\", line 51, in dispatch_proxy\n    response = conn.getresponse()\n               ^^^^^^^^^^^^^^^^^^\n  File \"C:\\Python311\\Lib\\http\\client.py\", line 1390, in getresponse\n    response.begin()\n  File \"C:\\Python311\\Lib\\http\\client.py\", line 325, in begin\n    version, status, reason = self._read_status()\n                              ^^^^^^^^^^^^^^^^^^^\n  File \"C:\\Python311\\Lib\\http\\client.py\", line 286, in _read_status\n    line = str(self.fp.readline(_MAXLINE + 1), \"iso-8859-1\")\n               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\n  File \"C:\\Python311\\Lib\\socket.py\", line 706, in readinto\n    return self._sock.recv_into(b)\n           ^^^^^^^^^^^^^^^^^^^^^^^\nConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host\n","data":"[WinError 10054] An existing connection was forcibly closed by the remote host"}} { metadata: undefined }

Here is the settings from claude_desktop_config.json, already tried native python environment but no luck as well:

{
  "mcpServers": {
    "ida-pro-mcp": {
      "command": "C:\\Users\\tuandm4\\mcp_env\\Scripts\\python.exe",
      "args": [
        "C:\\Users\\tuandm4\\mcp_env\\Lib\\site-packages\\ida_pro_mcp\\server.py",
        "--ida-rpc",
        "http://127.0.0.1:13337"
      ]
    }
  }
}

Already set up the plugin and turn on in IDA Pro:

The MCP Server appears in UI or the list of MCP Servers in other cli tools, but can't seems to run normally to interact with the opened IDA Pro process.

And ideas on the potential error? Thanks!

[Entropt]

I forgot to mention, the installation directory of Python is C:\Python311

[mrexodia]

[WinError 10054] An existing connection was forcibly closed by the remote host

Seems like a rather clear error, the code cannot connect to the socket inside of IDA? Can you open the config.html listed in the log after starting the MCP server?

[Entropt]

Here is the output from a simple curl command:

C:\Users\tuandm4>curl -v -i http://127.0.0.1:13337/config.html
*   Trying 127.0.0.1:13337...
* Connected to 127.0.0.1 (127.0.0.1) port 13337
* using HTTP/1.x
> GET /config.html HTTP/1.1
> Host: 127.0.0.1:13337
> User-Agent: curl/8.13.0
> Accept: */*
>
* abort upload
* Empty reply from server
* shutting down connection #0
curl: (52) Empty reply from server

I did install as the instruction, I ran cmd as Administrator:

pip uninstall ida-pro-mcp
pip install https://github.com/mrexodia/ida-pro-mcp/archive/refs/heads/main.zip
ida-pro-mcp --install

I also debug using @modelcontextprotocol/inspector, but 2 connection modes also both do not work.
Did I miss something in the MCP Plugin of IDA Pro?

[mrexodia]

There is likely something else listening on that port, check that and stop it.

[Entropt]

Yes, the root cause is actually another program listening on on port 13337, thank you