fix(test-conformance): stop leaking the conformance server and hanging on stale ports (#2276)

test/conformance/README.md

@@ -60,6 +60,8 @@ npx @modelcontextprotocol/conformance server \
   --scenario server-initialize
 ```
 
+Note: `pnpm run test:conformance:server` always starts (and tests) its own server, and refuses to run while anything is still listening on its port. Stop the manually started server first, or keep using the direct `--url` invocation above against it.
+
 ## Files
 
 - `src/everythingClient.ts` - Client that handles all client conformance scenarios

test/conformance/package.json

@@ -28,13 +28,13 @@
         "start": "npm run server",
         "server": "tsx watch --clear-screen=false scripts/cli.ts server",
         "client": "tsx scripts/cli.ts client",
-        "test:conformance:client": "conformance client --command 'npx tsx ./src/everythingClient.ts' --expected-failures ./expected-failures.yaml",
-        "test:conformance:client:all": "conformance client --command 'npx tsx ./src/everythingClient.ts' --suite all --expected-failures ./expected-failures.yaml",
-        "test:conformance:client:run": "npx tsx ./src/everythingClient.ts",
+        "test:conformance:client": "conformance client --command 'node --import tsx ./src/everythingClient.ts' --suite core --expected-failures ./expected-failures.yaml",
+        "test:conformance:client:all": "conformance client --command 'node --import tsx ./src/everythingClient.ts' --suite all --expected-failures ./expected-failures.yaml",
+        "test:conformance:client:run": "node --import tsx ./src/everythingClient.ts",
         "test:conformance:server": "scripts/run-server-conformance.sh --expected-failures ./expected-failures.yaml",
         "test:conformance:server:draft": "scripts/run-server-conformance.sh --suite draft --expected-failures ./expected-failures.yaml",
         "test:conformance:server:all": "scripts/run-server-conformance.sh --suite all --expected-failures ./expected-failures.yaml",
-        "test:conformance:server:run": "npx tsx ./src/everythingServer.ts",
+        "test:conformance:server:run": "node --import tsx ./src/everythingServer.ts",
         "test:conformance:all": "pnpm run test:conformance:client:all && pnpm run test:conformance:server:all"
     },
     "devDependencies": {
@@ -50,6 +50,7 @@
         "@modelcontextprotocol/test-helpers": "workspace:^",
         "cors": "catalog:runtimeServerOnly",
         "express": "catalog:runtimeServerOnly",
+        "tsx": "catalog:devTools",
         "zod": "catalog:runtimeShared"
     }
 }

test/conformance/scripts/run-server-conformance.sh

@@ -11,9 +11,21 @@ SERVER_URL="http://localhost:${PORT}/mcp"
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 cd "$SCRIPT_DIR/.."
 
-# Start the server in the background
+# Refuse to start if something is already listening on the port. The readiness
+# check below cannot tell our server apart from a stale one, so a leftover
+# listener would mean silently running conformance against old code — or
+# hanging forever if the listener never responds.
+if (: > "/dev/tcp/localhost/${PORT}") 2>/dev/null; then
+    echo "Error: port ${PORT} is already in use."
+    echo "Stop the stale process first (lsof -ti:${PORT} -sTCP:LISTEN | xargs kill) or set PORT to a free port."
+    exit 1
+fi
+
+# Start the server in the background. Use `node --import tsx` rather than
+# `npx tsx` so SERVER_PID is the server process itself — killing an npx/tsx
+# wrapper leaves the actual server running and squatting the port.
 echo "Starting conformance test server on port ${PORT}..."
-npx tsx ./src/everythingServer.ts &
+node --import tsx ./src/everythingServer.ts &
 SERVER_PID=$!
 
 # Function to cleanup on exit
@@ -24,11 +36,16 @@ cleanup() {
 }
 trap cleanup EXIT
 
-# Wait for server to be ready
+# Wait for server to be ready. --max-time keeps a hung listener from wedging
+# the loop forever, and a dead server process fails fast instead of retrying.
 echo "Waiting for server to be ready..."
 MAX_RETRIES=30
 RETRY_COUNT=0
-while ! curl -s "${SERVER_URL}" > /dev/null 2>&1; do
+while ! curl -s --max-time 2 "${SERVER_URL}" > /dev/null 2>&1; do
+    if ! kill -0 $SERVER_PID 2>/dev/null; then
+        echo "Server process exited unexpectedly"
+        exit 1
+    fi
     RETRY_COUNT=$((RETRY_COUNT + 1))
     if [ $RETRY_COUNT -ge $MAX_RETRIES ]; then
         echo "Server failed to start after ${MAX_RETRIES} attempts"

test/conformance/src/authTestServer.ts

@@ -412,12 +412,19 @@ async function startServer() {
     });
 
     // Start server
-    app.listen(PORT, () => {
+    const httpServer = app.listen(PORT, () => {
         console.log(`MCP Auth Test Server running at http://localhost:${PORT}/mcp`);
         console.log(`  - PRM endpoint: http://localhost:${PORT}/.well-known/oauth-protected-resource`);
         console.log(`  - Auth server: ${AUTH_SERVER_URL}`);
         console.log(`  - Introspection: ${asMetadata.introspection_endpoint}`);
     });
+    httpServer.on('error', (error: NodeJS.ErrnoException) => {
+        if (error.code !== 'EADDRINUSE') {
+            throw error;
+        }
+        console.error(`Port ${PORT} is already in use — is a stale auth test server still running?`);
+        process.exit(1);
+    });
 }
 
 // Start the server

test/conformance/src/everythingServer.ts

@@ -1020,7 +1020,14 @@ app.delete('/mcp', async (req: Request, res: Response) => {
 
 // Start server
 const PORT = process.env.PORT || 3000;
-app.listen(PORT, () => {
+const httpServer = app.listen(PORT, () => {
     console.log(`MCP Conformance Test Server running on http://localhost:${PORT}`);
     console.log(`  - MCP endpoint: http://localhost:${PORT}/mcp`);
 });
+httpServer.on('error', (error: NodeJS.ErrnoException) => {
+    if (error.code !== 'EADDRINUSE') {
+        throw error;
+    }
+    console.error(`Port ${PORT} is already in use — is a stale conformance server still running?`);
+    process.exit(1);
+});