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MCP servers can not be accessed via Docker and docker-compose anymore. #790

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MCP servers can not be accessed via Docker and docker-compose anymore.#790
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@Vildnex
Vildnex
opened on May 23, 2025

Since the last update to version 1.9.1, any of the Docker setups that run any MCP servers are not working anymore.
This bug is because since 1.9.1, the host from line 90 in the mcp/server/fastmcp/server.py was set to be 127.0.0.1 instead of 0.0.0.0, which was in the beginning.

Is there a workaround to fix the Docker setups, or can a rollback be done to use the 0.0.0.0 again?

Currently, the only fix I found is to set all the Docker setups to use the older version 1.9.0

Activity

  1. wkwi2r commented on May 26, 2025

    @wkwi2r
    wkwi2r
    on May 26, 2025

    I'm facing the exact same issue as my n8n workflows are no longer able to connect to the MCP server with 1.9.1

  2. liquidhair commented on May 26, 2025

    @liquidhair
    liquidhair
    on May 26, 2025

    im sorry but this is getting ridiculous everytime i configure a new setup either with docker or outside of it something else needs a workaround. This is not rocket science just seems that N8N is doing everything to prevent self hosting with making it extremely difficult to have a cohesive setup
    . Any advice on how to downgrade my containers in Docker to previous version?

  3. Vildnex commented on May 26, 2025

    @Vildnex
    Vildnex
    on May 26, 2025
    Author

    @liquidhair, if you already have the containers and images created, I would suggest just changing that line I am talking about in the issue and restarting the containers afterward. This should do the trick for you. The other option is to rebuild the images with the previous version 1.9.0, this is what I did for my case.

  4. wkwi2r commented on May 30, 2025

    @wkwi2r
    wkwi2r
    on May 30, 2025

    I found a solution: define an environment variable FASTMCP_HOST=0.0.0.0

    This works for latest release v1.9.2

  5. cbcoutinho commented on Aug 14, 2025

    @cbcoutinho
    cbcoutinho
    on Aug 14, 2025
    Contributor

    Using FASTMCP_HOST=0.0.0.0 is broken since #1198 (v.1.12.3) , and using this to override the host no longer works

  6. maxisbey
    added
    bugSomething isn't working
    needs confirmationNeeds confirmation that the PR is actually required or needed.
    questionFurther information is requested
    and removed
    bugSomething isn't working
    on Sep 26, 2025

  7. maxisbey commented on Sep 26, 2025

    @maxisbey
    maxisbey
    on Sep 26, 2025
    Contributor

    As of #1198 the SDK's FastMCP no longer pulls in configuration from environment variables. The service you implement can instead pull in configuration on its own from environment variables.

    Although there is active discussion about bringing the previous functionality back here: #1244

    For now, I'm going to close this issue in favour of the other discussion thread.

  8. maxisbey
    closed this as completedon Sep 26, 2025
  9. maxisbey
    reopened this on Sep 26, 2025
  10. maxisbey
    closed this as completedon Sep 26, 2025
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