Connection Error - Check if your MCP server is running and proxy token is correct

[yidasanqian]

mcp.run(transport="streamable-http")

log:

uv run mcp dev src/gen_images/bailian_mcpserver.py
Starting MCP inspector...
⚙️ Proxy server listening on localhost:6277
🔑 Session token: e05a5b929cf9f30564653a3411b3f4df6e55110e9d0383f3bb5000b680bb9a75
   Use this token to authenticate requests or set DANGEROUSLY_OMIT_AUTH=true to disable auth

🚀 MCP Inspector is up and running at:
   http://localhost:6274/?MCP_PROXY_AUTH_TOKEN=e05a5b929cf9f30564653a3411b3f4df6e55110e9d0383f3bb5000b680bb9a75

🌐 Opening browser...
New StreamableHttp connection request
Query parameters: {"url":"http://localhost:8000/mcp","transportType":"streamable-http"}
Created StreamableHttp server transport
Created StreamableHttp client transport
Client <-> Proxy  sessionId: a02ed93f-b1b9-49a3-8358-04018aa03101
Connection refused. Is the MCP server running?

how to fix?

[olaservo]

Hi @yidasanqian I'm testing latest Inspector with the latest Everything server using streamable http, and I can't repro your issue. So I think the issue might be with your server code - could you share that?

Here's what I tested with successfully:

To run inspector: npx -y @modelcontextprotocol/inspector@latest

To run the demo server: npx -y @modelcontextprotocol/server-everything@latest streamableHttp

[kartheekgp]

I know this issue is closed but I am still commenting in case anyone else is stuck in tutorial like me.
I had not installed uv. I was using venv to create a new environment.
Just installing uv solved my problem.
pip install uv

[maick400]

@kartheekgp thanks man, I solved too :)

[himanshuchuriwala]

still facing the same issue. using STDIO

[marksmith-II]

I'm also struggling to progress in the tutorial. I'm following the recommended setup instructions in the README.md file with no luck.

Here is my server code as well.

`from pydantic import Field # type: ignore
from mcp.server.fastmcp import FastMCP # type: ignore

mcp = FastMCP("DocumentMCP", log_level="ERROR")

docs = {
"deposition.md": "This deposition covers the testimony of Angela Smith, P.E.",
"report.pdf": "The report details the state of a 20m condenser tower.",
"financials.docx": "These financials outline the project's budget and expenditures.",
"outlook.pdf": "This document presents the projected future performance of the system.",
"plan.md": "The plan outlines the steps for the project's implementation.",
"spec.txt": "These specifications define the technical requirements for the equipment.",
}

@mcp.tool(
name="read_doc_contents",
description="Reads the contents of a specified document and returns it as a string.",
)
def read_document(
doc_id: str = Field(description="The ID of the document to read."),
):

if doc_id not in docs:
    raise ValueError(f"Document with ID '{doc_id}' not found.")
return docs[doc_id] 

@mcp.tool(
name="edit_document",
description="Edits the contents of a specified document with new content.",
)
def edit_document(
doc_id: str = Field(description="The ID of the document to edit."),
old_str: str = Field(description="The string to be replaced in the document."),
new_str: str = Field(description="The new content to write into the document."),
):
if doc_id not in docs:
raise ValueError(f"Document with ID '{doc_id}' not found.")
docs[doc_id] = docs[doc_id].replace(old_str, new_str)
return f"Document '{doc_id}' has been updated."

TODO: Write a resource to return all doc id's

TODO: Write a resource to return the contents of a particular doc

TODO: Write a prompt to rewrite a doc in markdown format

TODO: Write a prompt to summarize a doc

if name == "main":
mcp.run(transport="stdio")

`

[marksmith-II]

I know this issue is closed but I am still commenting in case anyone else is stuck in tutorial like me. I had not installed uv. I was using venv to create a new environment. Just installing uv solved my problem. pip install uv

Unfortunately, this route isn't working for me. Any other suggestions?

[priye-1]

I know this issue is closed but I am still commenting in case anyone else is stuck in tutorial like me. I had not installed uv. I was using venv to create a new environment. Just installing uv solved my problem. pip install uv

Thank youu, worked for me as well @kartheekgp