From df8051b975778a17381bf32d093bc1f29bd47e85 Mon Sep 17 00:00:00 2001
From: Ashwin Bhat <ashwin@anthropic.com>
Date: Thu, 10 Oct 2024 09:13:19 -0700
Subject: [PATCH] use proxy function

---
 server/src/index.ts    | 81 ++++++------------------------------------
 server/src/mcpProxy.ts | 30 ++++++++++++++++
 2 files changed, 40 insertions(+), 71 deletions(-)
 create mode 100644 server/src/mcpProxy.ts

diff --git a/server/src/index.ts b/server/src/index.ts
index 547c483..902ee03 100644
--- a/server/src/index.ts
+++ b/server/src/index.ts
@@ -3,22 +3,9 @@ import cors from "cors";
 import { Server } from "mcp-typescript/server/index.js";
 import { SSEServerTransport } from "mcp-typescript/server/sse.js";
 import express from "express";
-import {
-  CallToolRequestSchema,
-  GetPromptRequestSchema,
-  ListPromptsRequestSchema,
-  ListResourcesRequestSchema,
-  ListToolsRequestSchema,
-  ReadResourceRequestSchema,
-  ListResourcesResultSchema,
-  ReadResourceResultSchema,
-  ListPromptsResultSchema,
-  GetPromptResultSchema,
-  ListToolsResultSchema,
-  CallToolResultSchema,
-} from "mcp-typescript/types.js";
 import { Client } from "mcp-typescript/client/index.js";
 import { StdioClientTransport } from "mcp-typescript/client/stdio.js";
+import mcpProxy from "./mcpProxy.js";
 
 const app = express();
 app.use(cors());
@@ -47,65 +34,17 @@ app.get("/sse", async (req, res) => {
     await mcpClient.close();
   };
 
-  server.setRequestHandler(ListResourcesRequestSchema, () =>
-    mcpClient.request(
-      {
-        method: "resources/list",
-      },
-      ListResourcesResultSchema,
-    ),
-  );
-
-  server.setRequestHandler(ReadResourceRequestSchema, (params) =>
-    mcpClient.request(
-      {
-        method: "resources/read",
-        params: params.params,
-      },
-      ReadResourceResultSchema,
-    ),
-  );
-
-  server.setRequestHandler(ListPromptsRequestSchema, () =>
-    mcpClient.request(
-      {
-        method: "prompts/list",
-      },
-      ListPromptsResultSchema,
-    ),
-  );
-
-  server.setRequestHandler(GetPromptRequestSchema, (params) => {
-    return mcpClient.request(
-      {
-        method: "prompts/get",
-        params: params.params,
-      },
-      GetPromptResultSchema,
-    );
-  });
-
-  server.setRequestHandler(ListToolsRequestSchema, () =>
-    mcpClient.request(
-      {
-        method: "tools/list",
-      },
-      ListToolsResultSchema,
-    ),
-  );
-
-  server.setRequestHandler(CallToolRequestSchema, (params) =>
-    mcpClient.request(
-      {
-        method: "tools/call",
-        params: params.params,
-      },
-      CallToolResultSchema,
-    ),
-  );
-
   await webAppTransport.connectSSE(req, res);
   await server.connect(webAppTransport);
+
+  mcpProxy({
+    transportToClient: webAppTransport,
+    transportToServer: backingServerTransport,
+    onerror: (error) => {
+      console.error(error);
+      server.close();
+    },
+  });
 });
 
 app.post("/message", async (req, res) => {
diff --git a/server/src/mcpProxy.ts b/server/src/mcpProxy.ts
new file mode 100644
index 0000000..e6c4124
--- /dev/null
+++ b/server/src/mcpProxy.ts
@@ -0,0 +1,30 @@
+import { Transport } from "mcp-typescript/shared/transport.js";
+
+export default function mcpProxy({
+  transportToClient,
+  transportToServer,
+  onerror,
+}: {
+  transportToClient: Transport;
+  transportToServer: Transport;
+  onerror: (error: Error) => void;
+}) {
+  transportToClient.onmessage = (message) => {
+    transportToServer.send(message).catch(onerror);
+  };
+
+  transportToServer.onmessage = (message) => {
+    transportToClient.send(message).catch(onerror);
+  };
+
+  transportToClient.onclose = () => {
+    transportToServer.close().catch(onerror);
+  };
+
+  transportToServer.onclose = () => {
+    transportToClient.close().catch(onerror);
+  };
+
+  transportToClient.onerror = onerror;
+  transportToServer.onerror = onerror;
+}