Feature: Add WebSocket Transport for MCP Servers #3017
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servers using the WebSocket transport
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DouweM
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Sep 30, 2025
| return self.url == value.url | ||
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| class MCPServerWebSocket(_MCPServerHTTP): |
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Should this inherit from MCPServer instead of _MCPServerHTTP if it overrides most of what that class does?
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@Kludex Would it make sense to support this while modelcontextprotocol/modelcontextprotocol#1288 is still in review, but the feature is available on the Python SDK? |
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@DouweM Thanks for pointing that out. Since this feature is still under review in modelcontextprotocol/modelcontextprotocol#1288, I agree it makes sense to hold off until it becomes production-ready. I’ll keep track of its progress in the MCP repo and update this PR once it’s a stable feature we can reliably depend on. |
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Closes #3016
Description:
Summary
This pull request introduces support for WebSocket as a transport mechanism for MCP servers by adding a new
MCPServerWebSocketclass. This provides a robust alternative to the existing HTTP-based transports (SSE and Streamable HTTP).Motivation
In many production environments, especially within containerized services like Kubernetes, HTTP-based transports can lead to challenges with session management and load balancing. Sticky sessions are often required to ensure that requests for a given session ID are routed to the same pod, which can cause uneven load distribution and complications when pods are restarted or scaled.
As detailed in #3016 , using WebSockets for the MCP connection establishes a stable, long-lived, and stateful connection between the client and a specific server instance. This avoids the need for complex load balancer configurations and resolves issues related to session persistence being "nailed to the pod," leading to a more resilient and scalable architecture.
This implementation directly addresses feedback from users who rely on WebSockets as their primary connection method for MCP servers.