fix(node): handle EADDRINUSE port conflict on serve

src/adapters/node.ts

@@ -62,7 +62,6 @@ class NodeServer implements Server {
     errorPlugin(this);
 
     const fetchHandler = (this.fetch = wrapFetch(this));
-
     const handler = (nodeReq: NodeServerRequest, nodeRes: NodeServerResponse) => {
       const request = new NodeRequest({ req: nodeReq, res: nodeRes });
       request.waitUntil = this.#wait?.waitUntil;
@@ -120,20 +119,37 @@ class NodeServer implements Server {
     this.node.server = server;
 
     if (!options.manual) {
-      this.serve();
+      this.serve().catch(() => {});
     }
   }
 
-  serve() {
+  serve(): Promise<this> {
     if (this.#listeningPromise) {
-      return Promise.resolve(this.#listeningPromise).then(() => this);
+      return this.#listeningPromise.then(() => this);
     }
-    this.#listeningPromise = new Promise<void>((resolve) => {
-      this.node!.server!.listen(this.serveOptions, () => {
+
+    const server = this.node?.server as
+      | NodeHttp.Server
+      | NodeHttps.Server
+      | NodeHttp2.Http2SecureServer;
+    this.#listeningPromise = new Promise<void>((resolve, reject) => {
+      const onError = (error: Error) => {
+        server.off("listening", onListening);
+        reject(error);
+      };
+
+      const onListening = () => {
+        server.off("error", onError);
         printListening(this.options, this.url);
         resolve();
-      });
+      };
+
+      server.once("error", onError);
+      server.once("listening", onListening);
+      server.listen(this.serveOptions);
     });
+
+    return this.#listeningPromise.then(() => this);
   }
 
   get url() {

test/node-adapters.test.ts

@@ -1,4 +1,6 @@
+import { createServer } from "node:http";
 import { describe, expect, test } from "vitest";
+import { getRandomPort } from "get-port-please";
 
 import type { NodeHttp1Handler, NodeServerRequest, NodeServerResponse } from "../src/types.ts";
 import { fetchNodeHandler, serve, toNodeHandler, toFetchHandler } from "../src/adapters/node.ts";
@@ -257,3 +259,42 @@ describe("request signal", () => {
     await server.close(true); // Force close all connections
   });
 });
+
+describe("node server startup", () => {
+  test("port conflict rejects with EADDRINUSE", async () => {
+    const port = await getRandomPort("localhost");
+    const blocker = createServer((_req, res) => res.end("blocked"));
+
+    await new Promise<void>((resolve) => blocker.listen(port, "127.0.0.1", () => resolve()));
+
+    try {
+      const server = serve({
+        port,
+        hostname: "127.0.0.1",
+        manual: true,
+        fetch: () => new Response(""),
+      });
+      await expect(server.serve()).rejects.toMatchObject({ code: "EADDRINUSE" });
+    } finally {
+      await new Promise<void>((resolve) => blocker.close(() => resolve()));
+    }
+  });
+
+  test("auto-serve port conflict surfaces via ready()", async () => {
+    const port = await getRandomPort("localhost");
+    const blocker = createServer((_req, res) => res.end("blocked"));
+
+    await new Promise<void>((resolve) => blocker.listen(port, "127.0.0.1", () => resolve()));
+
+    try {
+      const server = serve({
+        port,
+        hostname: "127.0.0.1",
+        fetch: () => new Response(""),
+      });
+      await expect(server.ready()).rejects.toMatchObject({ code: "EADDRINUSE" });
+    } finally {
+      await new Promise<void>((resolve) => blocker.close(() => resolve()));
+    }
+  });
+});