select random ports if defaults are taken (#695)

* select random port if default ports are taken

* add changeset

5 files changed, 17 insertions, 6 deletions

diff --git a/.changeset/empty-otters-smell.md b/.changeset/empty-otters-smell.md
new file mode 100644
index 000000000..7c73a3b94
--- /dev/null
+++ b/.changeset/empty-otters-smell.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Allow multiple Astro servers to be running simultaneously by choosing random ports if the defaults are taken.
diff --git a/packages/astro/package.json b/packages/astro/package.json
index d3ec16d1a..bb970fa02 100644
--- a/packages/astro/package.json
+++ b/packages/astro/package.json
@@ -68,6 +68,7 @@
     "fast-xml-parser": "^3.19.0",
     "fdir": "^5.0.0",
     "find-up": "^5.0.0",
+    "get-port": "^5.1.1",
     "gzip-size": "^6.0.0",
     "hast-to-hyperscript": "~9.0.0",
     "kleur": "^4.1.4",
diff --git a/packages/astro/snowpack-plugin.cjs b/packages/astro/snowpack-plugin.cjs
index 30f381e56..3e1edecc7 100644
--- a/packages/astro/snowpack-plugin.cjs
+++ b/packages/astro/snowpack-plugin.cjs
@@ -1,4 +1,5 @@
 const { readFile } = require('fs').promises;
+const getPort = require('get-port');
 // Snowpack plugins must be CommonJS :(
 const transformPromise = import('./dist/compiler/index.js');
 
@@ -48,9 +49,12 @@ module.exports = (snowpackConfig, options = {}) => {
         configManager.markDirty();
       }
     },
-    config(snowpackConfig) {
+    async config(snowpackConfig) {
       if(!isNaN(snowpackConfig.devOptions.hmrPort)) {
         hmrPort = snowpackConfig.devOptions.hmrPort;
+      } else {
+        hmrPort = await getPort({ port: DEFAULT_HMR_PORT, host: snowpackConfig.devOptions.hostname });
+        snowpackConfig.devOptions.hmrPort = hmrPort;
       }
     },
     async load({ filePath }) {
diff --git a/packages/astro/src/config.ts b/packages/astro/src/config.ts
index a1e5556a4..7e2aeec4e 100644
--- a/packages/astro/src/config.ts
+++ b/packages/astro/src/config.ts
@@ -1,6 +1,7 @@
 import type { AstroConfig } from './@types/astro';
 import path from 'path';
 import { existsSync } from 'fs';
+import getPort from 'get-port';
 
 /** Type util */
 const type = (thing: any): string => (Array.isArray(thing) ? 'Array' : typeof thing);
@@ -48,7 +49,7 @@ function validateConfig(config: any): void {
 }
 
 /** Set default config values */
-function configDefaults(userConfig?: any): any {
+async function configDefaults(userConfig?: any): Promise<any> {
   const config: any = { ...(userConfig || {}) };
 
   if (!config.projectRoot) config.projectRoot = '.';
@@ -57,7 +58,7 @@ function configDefaults(userConfig?: any): any {
   if (!config.dist) config.dist = './dist';
   if (!config.public) config.public = './public';
   if (!config.devOptions) config.devOptions = {};
-  if (!config.devOptions.port) config.devOptions.port = 3000;
+  if (!config.devOptions.port) config.devOptions.port = await getPort({ port: getPort.makeRange(3000, 3050) });
   if (!config.buildOptions) config.buildOptions = {};
   if (!config.markdownOptions) config.markdownOptions = {};
   if (typeof config.buildOptions.sitemap === 'undefined') config.buildOptions.sitemap = true;
@@ -86,9 +87,9 @@ export async function loadConfig(rawRoot: string | undefined, configFileName = '
   // load
   let config: any;
   if (existsSync(astroConfigPath)) {
-    config = configDefaults((await import(astroConfigPath.href)).default);
+    config = await configDefaults((await import(astroConfigPath.href)).default);
   } else {
-    config = configDefaults();
+    config = await configDefaults();
   }
 
   // validate
diff --git a/yarn.lock b/yarn.lock
index 8634fb4f2..5865a2d02 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -4988,7 +4988,7 @@ get-pkg-repo@^1.0.0:
 
 get-port@^5.1.1:
   version "5.1.1"
-  resolved "https://registry.npmjs.org/get-port/-/get-port-5.1.1.tgz"
+  resolved "https://registry.yarnpkg.com/get-port/-/get-port-5.1.1.tgz#0469ed07563479de6efb986baf053dcd7d4e3193"
   integrity sha512-g/Q1aTSDOxFpchXC4i8ZWvxA1lnPqx/JHqcpIw0/LX9T8x/GBbi6YnlN5nhaKIFkT8oFsscUKgDJYxfwfS6QsQ==
 
 get-stdin@^4.0.1: