diff --git a/server/src/index.ts b/server/src/index.ts index 51e30a083..37327fa27 100644 --- a/server/src/index.ts +++ b/server/src/index.ts @@ -91,7 +91,7 @@ const serverTransports: Map = new Map(); / const createTransport = async (req: express.Request): Promise => { const query = req.query; - console.log("Query parameters:", query); + console.log("Query parameters:", JSON.stringify(query)); const transportType = query.transportType as string; @@ -103,7 +103,7 @@ const createTransport = async (req: express.Request): Promise => { const { cmd, args } = findActualExecutable(command, origArgs); - console.log(`Stdio transport: command=${cmd}, args=${args}`); + console.log(`STDIO transport: command=${cmd}, args=${args}`); const transport = new StdioClientTransport({ command: cmd, @@ -113,8 +113,6 @@ const createTransport = async (req: express.Request): Promise => { }); await transport.start(); - - console.log("Spawned stdio transport"); return transport; } else if (transportType === "sse") { const url = query.url as string; @@ -132,8 +130,6 @@ const createTransport = async (req: express.Request): Promise => { }, }); await transport.start(); - - console.log("Connected to SSE transport"); return transport; } else if (transportType === "streamable-http") { const headers = getHttpHeaders(req, transportType); @@ -147,7 +143,6 @@ const createTransport = async (req: express.Request): Promise => { }, ); await transport.start(); - console.log("Connected to Streamable HTTP transport"); return transport; } else { console.error(`Invalid transport type: ${transportType}`); @@ -176,11 +171,10 @@ app.get("/mcp", async (req, res) => { app.post("/mcp", async (req, res) => { const sessionId = req.headers["mcp-session-id"] as string | undefined; - console.log(`Received POST message for sessionId ${sessionId}`); let serverTransport: Transport | undefined; if (!sessionId) { try { - console.log("New streamable-http connection"); + console.log("New StreamableHttp connection request"); try { serverTransport = await createTransport(req); } catch (error) { @@ -196,16 +190,17 @@ app.post("/mcp", async (req, res) => { throw error; } - console.log("Connected MCP client to server transport"); + console.log("Created StreamableHttp server transport"); const webAppTransport = new StreamableHTTPServerTransport({ sessionIdGenerator: randomUUID, onsessioninitialized: (sessionId) => { webAppTransports.set(sessionId, webAppTransport); serverTransports.set(sessionId, serverTransport!); - console.log("Created streamable web app transport " + sessionId); + console.log("Client <-> Proxy sessionId: " + sessionId); }, }); + console.log("Created StreamableHttp client transport"); await webAppTransport.start(); @@ -224,6 +219,7 @@ app.post("/mcp", async (req, res) => { res.status(500).json(error); } } else { + console.log(`Received POST message for sessionId ${sessionId}`); try { const transport = webAppTransports.get( sessionId, @@ -272,15 +268,15 @@ app.delete("/mcp", async (req, res) => { app.get("/stdio", async (req, res) => { try { - console.log("New connection"); + console.log("New STDIO connection request"); let serverTransport: Transport | undefined; try { serverTransport = await createTransport(req); + console.log("Created server transport"); } catch (error) { if (error instanceof SseError && error.code === 401) { console.error( - "Received 401 Unauthorized from MCP server:", - error.message, + "Received 401 Unauthorized from MCP server. Authentication failure.", ); res.status(401).json(error); return; @@ -289,31 +285,43 @@ app.get("/stdio", async (req, res) => { throw error; } - console.log("Connected MCP client to backing server transport"); - const webAppTransport = new SSEServerTransport("/message", res); + console.log("Created client transport"); + webAppTransports.set(webAppTransport.sessionId, webAppTransport); serverTransports.set(webAppTransport.sessionId, serverTransport); - console.log("Created client/server transports"); await webAppTransport.start(); (serverTransport as StdioClientTransport).stderr!.on("data", (chunk) => { - webAppTransport.send({ - jsonrpc: "2.0", - method: "notifications/stderr", - params: { - content: chunk.toString(), - }, - }); + if (chunk.toString().includes("MODULE_NOT_FOUND")) { + webAppTransport.send({ + jsonrpc: "2.0", + method: "notifications/stderr", + params: { + content: "Command not found, transports removed", + }, + }); + webAppTransport.close(); + serverTransport.close(); + webAppTransports.delete(webAppTransport.sessionId); + serverTransports.delete(webAppTransport.sessionId); + console.error("Command not found, transports removed"); + } else { + webAppTransport.send({ + jsonrpc: "2.0", + method: "notifications/stderr", + params: { + content: chunk.toString(), + }, + }); + } }); mcpProxy({ transportToClient: webAppTransport, transportToServer: serverTransport, }); - - console.log("Set up MCP proxy"); } catch (error) { console.error("Error in /stdio route:", error); res.status(500).json(error); @@ -323,7 +331,7 @@ app.get("/stdio", async (req, res) => { app.get("/sse", async (req, res) => { try { console.log( - "New SSE connection. NOTE: The sse transport is deprecated and has been replaced by streamable-http", + "New SSE connection request. NOTE: The sse transport is deprecated and has been replaced by StreamableHttp", ); let serverTransport: Transport | undefined; try { @@ -331,32 +339,38 @@ app.get("/sse", async (req, res) => { } catch (error) { if (error instanceof SseError && error.code === 401) { console.error( - "Received 401 Unauthorized from MCP server:", - error.message, + "Received 401 Unauthorized from MCP server. Authentication failure.", ); res.status(401).json(error); return; + } else if (error instanceof SseError && error.code === 404) { + console.error( + "Received 404 not found from MCP server. Does the MCP server support SSE?", + ); + res.status(404).json(error); + return; + } else if (JSON.stringify(error).includes("ECONNREFUSED")) { + console.error("Connection refused. Is the MCP server running?"); + res.status(500).json(error); + } else { + throw error; } - - throw error; } - console.log("Connected MCP client to backing server transport"); + if (serverTransport) { + const webAppTransport = new SSEServerTransport("/message", res); + webAppTransports.set(webAppTransport.sessionId, webAppTransport); + console.log("Created client transport"); + serverTransports.set(webAppTransport.sessionId, serverTransport!); + console.log("Created server transport"); - const webAppTransport = new SSEServerTransport("/message", res); - webAppTransports.set(webAppTransport.sessionId, webAppTransport); - console.log("Created client transport"); - serverTransports.set(webAppTransport.sessionId, serverTransport); - console.log("Created server transport"); - - await webAppTransport.start(); - - mcpProxy({ - transportToClient: webAppTransport, - transportToServer: serverTransport, - }); + await webAppTransport.start(); - console.log("Set up MCP proxy"); + mcpProxy({ + transportToClient: webAppTransport, + transportToServer: serverTransport, + }); + } } catch (error) { console.error("Error in /sse route:", error); res.status(500).json(error); @@ -366,7 +380,7 @@ app.get("/sse", async (req, res) => { app.post("/message", async (req, res) => { try { const sessionId = req.query.sessionId; - console.log(`Received message for sessionId ${sessionId}`); + console.log(`Received POST message for sessionId ${sessionId}`); const transport = webAppTransports.get( sessionId as string, diff --git a/server/src/mcpProxy.ts b/server/src/mcpProxy.ts index 126605042..9dee9de41 100644 --- a/server/src/mcpProxy.ts +++ b/server/src/mcpProxy.ts @@ -6,7 +6,15 @@ function onClientError(error: Error) { } function onServerError(error: Error) { - console.error("Error from MCP server:", error); + if ( + (error?.message && + error.message.includes("Error POSTing to endpoint (HTTP 404)")) || + (error?.cause && JSON.stringify(error.cause).includes("ECONNREFUSED")) + ) { + console.error("Connection refused. Is the MCP server running?"); + } else { + console.error("Error from MCP server:", error); + } } export default function mcpProxy({ @@ -19,6 +27,8 @@ export default function mcpProxy({ let transportToClientClosed = false; let transportToServerClosed = false; + let reportedServerSession = false; + transportToClient.onmessage = (message) => { transportToServer.send(message).catch((error) => { // Send error response back to client if it was a request (has id) and connection is still open @@ -38,6 +48,15 @@ export default function mcpProxy({ }; transportToServer.onmessage = (message) => { + if (!reportedServerSession) { + if (transportToServer.sessionId) { + // Can only report for StreamableHttp + console.error( + "Proxy <-> Server sessionId: " + transportToServer.sessionId, + ); + } + reportedServerSession = true; + } transportToClient.send(message).catch(onClientError); };