SSE Timeout Error After 5 Minutes

Bug Reports
1

After running the AspNetCoreSseServer sample(csharp-sdk/samples/AspNetCoreSseServer at main · modelcontextprotocol/csharp-sdk · GitHub) with Cursor, I encounter the following error after 5 minutes of idle time:

SSE error: TypeError: terminated: Body Timeout Error`

To Reproduce
Steps to reproduce the behavior:

  1. Run the sample SSE server:
    cd samples/AspNetCoreSseServer && dotnet run --configuration Debug
  2. Register the server in MCP config:
    { "mcpServers": { "sse-test-5": { "url": "http://localhost:3001/sse" } } }
  3. Observe that it connects successfully and appears online in Cursor
  4. Wait for 5 minutes (no interaction)
  5. Observe the error:
    SSE error: TypeError: terminated: Body Timeout Error

Expected behavior
The SSE connection should remain open indefinitely (or at least longer than 5 minutes) if idle, without triggering a timeout or client termination error.

Logs

SSE Server Logs:
info: Microsoft.Hosting.Lifetime[14]
Now listening on: http://localhost:3001
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Development
info: Microsoft.Hosting.Lifetime[0]
Content root path: /Users/shaykeren/work/csharp-sdk/samples/AspNetCoreSseServer
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0) method ‘initialize’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘initialize’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0) method ‘initialize’ request handler called.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0) method ‘initialize’ request handler called.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0) method ‘initialize’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘initialize’ request handler completed.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘initialize’ request handler completed.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘initialize’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) method ‘tools/list’ request handler completed.
info: ModelContextProtocol.Server.McpServer[2103773711]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) message processing canceled.
info: ModelContextProtocol.Server.McpServer[2081236114]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) shutting down.
info: ModelContextProtocol.Server.McpServer[613617602]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) shut down.
info: ModelContextProtocol.Server.McpServer[2103773711]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) message processing canceled.
info: ModelContextProtocol.Server.McpServer[2081236114]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) shutting down.
info: ModelContextProtocol.Server.McpServer[613617602]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) shut down.
info: ModelContextProtocol.Server.McpServer[2103773711]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) message processing canceled.
info: ModelContextProtocol.Server.McpServer[2081236114]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) shutting down.
info: ModelContextProtocol.Server.McpServer[613617602]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) shut down.
info: ModelContextProtocol.Server.McpServer[2103773711]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) message processing canceled.
info: ModelContextProtocol.Server.McpServer[2081236114]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) shutting down.
info: ModelContextProtocol.Server.McpServer[613617602]
Server (AspNetCoreSseServer 1.0.0.0), Client (cursor-vscode 1.0.0) shut down.

Cursor MCP Output:
2025-04-23 08:21:43.090 [info] test: Reusing existing sse client
2025-04-23 08:21:43.090 [info] test: Connected to sse server, fetching offerings
2025-04-23 08:21:43.094 [info] listOfferings: Found 2 tools
2025-04-23 08:21:43.094 [info] test: Found 2 tools, 0 resources, and 0 resource templates
2025-04-23 08:21:43.095 [info] -mcp: Client closed for command
2025-04-23 08:21:43.095 [error] -mcp: Error in MCP: Client closed
2025-04-23 08:21:43.096 [info] test: Handling CreateClient action
2025-04-23 08:21:43.096 [info] test: getOrCreateClient for sse server. process.platform: darwin isElectron: true
2025-04-23 08:21:43.096 [info] test: Reusing existing sse client
2025-04-23 08:21:43.097 [info] -mcp: Handling ListOfferings action
2025-04-23 08:21:43.097 [error] -mcp: No server info found
2025-04-23 08:21:43.097 [info] test: Handling ListOfferings action
2025-04-23 08:21:43.097 [info] test: Listing offerings
2025-04-23 08:21:43.097 [info] test: getOrCreateClient for sse server. process.platform: darwin isElectron: true
2025-04-23 08:21:43.097 [info] test: Reusing existing sse client
2025-04-23 08:21:43.097 [info] test: Connected to sse server, fetching offerings
2025-04-23 08:21:43.101 [info] listOfferings: Found 2 tools
2025-04-23 08:21:43.101 [info] test: Found 2 tools, 0 resources, and 0 resource templates
2025-04-23 08:21:43.152 [info] -mcp: Client closed for command
2025-04-23 08:21:43.152 [error] -mcp: Error in MCP: Client closed
2025-04-23 08:21:43.170 [info] -mcp: Client closed for command
2025-04-23 08:21:43.170 [error] -mcp: Error in MCP: Client closed
2025-04-23 08:26:45.289 [error] test: Client error for command SSE error: TypeError: terminated: Body Timeout Error
2025-04-23 08:26:45.290 [error] test: Error in MCP: SSE error: TypeError: terminated: Body Timeout Error

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