fix(server-runtime): ignore duplicate websocket listener (#1829)

packages/server-runtime/src/server.test.ts

@@ -90,6 +90,19 @@ describe('createServer', async () => {
     await retryStart
   })
 
+  it('treats EADDRINUSE as an existing listener instead of failing startup', async () => {
+    const server = createServer({ hostname: '127.0.0.1', port: 6121 })
+
+    const startTask = server.start()
+    const error = new Error('listen EADDRINUSE: address already in use 127.0.0.1:6121') as NodeJS.ErrnoException
+    error.code = 'EADDRINUSE'
+    serveMocks.rejectServe(error)
+
+    await expect(startTask).resolves.toBeUndefined()
+    expect(serveMocks.disposeCall).toHaveBeenCalledTimes(1)
+    expect(serveMocks.closeCall).toHaveBeenCalledWith(true)
+  })
+
   it('merges nested config updates instead of replacing sibling logger settings', async () => {
     const server = createServer({
       hostname: '127.0.0.1',

packages/server-runtime/src/server/index.ts

@@ -32,6 +32,13 @@ export interface Server {
   updateConfig: (newOptions: ServerOptions) => void
 }
 
+function isAddressInUseError(error: unknown) {
+  return typeof error === 'object'
+    && error !== null
+    && 'code' in error
+    && (error as NodeJS.ErrnoException).code === 'EADDRINUSE'
+}
+
 /**
  * Collects local IP addresses that can be used to reach the server from the LAN.
  *
@@ -189,6 +196,10 @@ export function createServer(opts?: ServerOptions): Server {
         serverInstance = null
         h3App.dispose()
         await instance.close(true).catch(() => {})
+        if (isAddressInUseError(error)) {
+          log.withError(error).warn('WebSocket server port already in use, assuming an existing listener is available')
+          return
+        }
         log.withError(error).error('failed to start WebSocket server')
         throw error
       }