fix: handle EPIPE and ERR_STREAM_DESTROYED in StdioServerTransport#1679
Open
kai-agent-free wants to merge 2 commits intomodelcontextprotocol:mainfrom
Open
fix: handle EPIPE and ERR_STREAM_DESTROYED in StdioServerTransport#1679kai-agent-free wants to merge 2 commits intomodelcontextprotocol:mainfrom
kai-agent-free wants to merge 2 commits intomodelcontextprotocol:mainfrom
Conversation
When a client disconnects abruptly, stdout.write() can emit an EPIPE or ERR_STREAM_DESTROYED error that crashes the server process. This adds: - An error listener on stdout that catches EPIPE/ERR_STREAM_DESTROYED and triggers graceful close() instead of crashing - try/catch in send() for synchronous write errors - A writable check before writing - Cleanup of the stdout error listener in close() Fixes modelcontextprotocol#1564
🦋 Changeset detectedLatest commit: 9a96b23 The changes in this PR will be included in the next version bump. This PR includes changesets to release 4 packages
Not sure what this means? Click here to learn what changesets are. Click here if you're a maintainer who wants to add another changeset to this PR |
@modelcontextprotocol/client
@modelcontextprotocol/server
@modelcontextprotocol/express
@modelcontextprotocol/hono
@modelcontextprotocol/node
commit: |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Problem
When an MCP client disconnects abruptly (closes stdin/stdout pipes),
StdioServerTransport.send()throws an unhandled EPIPE error that fatally crashes the Node.js process. This is a DoS vector for any MCP server using stdio transport.Solution
Minimal change to
StdioServerTransport:Added
_onstdouterrorlistener — registered onstdoutinstart(), catchesEPIPEandERR_STREAM_DESTROYEDerrors and callsclose()gracefully instead of letting them propagate as unhandled exceptions. Other errors are forwarded toonerror.Added error handling in
send()— checksstdout.writablebefore writing, and wrapswrite()in try/catch for synchronous throw protection.Cleanup in
close()— removes the stdout error listener to prevent leaks.Tests
Added 5 new tests:
All existing tests continue to pass.
Fixes #1564