From 427b4680864e5d14f2e4f857c0e697675cd8434e Mon Sep 17 00:00:00 2001
From: xsbchen <xsbchen@qq.com>
Date: Wed, 10 Apr 2019 17:48:53 +0800
Subject: [PATCH 1/2] just use portfinder when user not set port

---
 packages/@vue/cli-service/lib/commands/serve.js | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/packages/@vue/cli-service/lib/commands/serve.js b/packages/@vue/cli-service/lib/commands/serve.js
index 0852171c5b..8a9da103dc 100644
--- a/packages/@vue/cli-service/lib/commands/serve.js
+++ b/packages/@vue/cli-service/lib/commands/serve.js
@@ -76,8 +76,12 @@ module.exports = (api, options) => {
     const useHttps = args.https || projectDevServerOptions.https || defaults.https
     const protocol = useHttps ? 'https' : 'http'
     const host = args.host || process.env.HOST || projectDevServerOptions.host || defaults.host
-    portfinder.basePort = args.port || process.env.PORT || projectDevServerOptions.port || defaults.port
-    const port = await portfinder.getPortPromise()
+    let port = args.port || process.env.PORT || projectDevServerOptions.port
+    // just use portfinder when user not set port
+    if (!port) {
+      portfinder.basePort = defaults.port
+      port = await portfinder.getPortPromise()
+    }
     const rawPublicUrl = args.public || projectDevServerOptions.public
     const publicUrl = rawPublicUrl
       ? /^[a-zA-Z]+:\/\//.test(rawPublicUrl)

From c883eb18529897b86810e7b5ee4f08bdc5b22412 Mon Sep 17 00:00:00 2001
From: xsbchen <xsbchen@qq.com>
Date: Wed, 10 Apr 2019 19:47:56 +0800
Subject: [PATCH 2/2] feat(serve): add error handler & console message

---
 packages/@vue/cli-service/lib/commands/serve.js | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/packages/@vue/cli-service/lib/commands/serve.js b/packages/@vue/cli-service/lib/commands/serve.js
index 8a9da103dc..81f319e36b 100644
--- a/packages/@vue/cli-service/lib/commands/serve.js
+++ b/packages/@vue/cli-service/lib/commands/serve.js
@@ -1,5 +1,6 @@
 const {
   info,
+  error,
   hasProjectYarn,
   openBrowser,
   IpcMessenger
@@ -77,8 +78,10 @@ module.exports = (api, options) => {
     const protocol = useHttps ? 'https' : 'http'
     const host = args.host || process.env.HOST || projectDevServerOptions.host || defaults.host
     let port = args.port || process.env.PORT || projectDevServerOptions.port
+    let hasUserGivenPort = true
     // just use portfinder when user not set port
     if (!port) {
+      hasUserGivenPort = false
       portfinder.basePort = defaults.port
       port = await portfinder.getPortPromise()
     }
@@ -280,6 +283,14 @@ module.exports = (api, options) => {
         if (err) {
           reject(err)
         }
+      }).on('error', err => {
+        if (hasUserGivenPort && err.code === 'EADDRINUSE') {
+          console.log()
+          error(`Address already in use ${err.address}:${err.port}.`)
+          info(`You can change the port by ${chalk.cyan('--port')} option or ${chalk.cyan('vue.config.js')} or ${chalk.cyan('package.json')}.`)
+          process.exit(1)
+        }
+        reject(err)
       })
     })
   })